| 1 | \input texinfo @c -*-Texinfo-*- |
| 2 | @c Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 1998 |
| 3 | @c Free Software Foundation, Inc. |
| 4 | @c UPDATE!! On future updates-- |
| 5 | @c (1) check for new machine-dep cmdline options in |
| 6 | @c md_parse_option definitions in config/tc-*.c |
| 7 | @c (2) for platform-specific directives, examine md_pseudo_op |
| 8 | @c in config/tc-*.c |
| 9 | @c (3) for object-format specific directives, examine obj_pseudo_op |
| 10 | @c in config/obj-*.c |
| 11 | @c (4) portable directives in potable[] in read.c |
| 12 | @c %**start of header |
| 13 | @setfilename as.info |
| 14 | @c ---config--- |
| 15 | @c defaults, config file may override: |
| 16 | @set have-stabs |
| 17 | @c --- |
| 18 | @include asconfig.texi |
| 19 | @include gasver.texi |
| 20 | @c --- |
| 21 | @c common OR combinations of conditions |
| 22 | @ifset AOUT |
| 23 | @set aout-bout |
| 24 | @end ifset |
| 25 | @ifset ARM/Thumb |
| 26 | @set ARM |
| 27 | @end ifset |
| 28 | @ifset BOUT |
| 29 | @set aout-bout |
| 30 | @end ifset |
| 31 | @ifset H8/300 |
| 32 | @set H8 |
| 33 | @end ifset |
| 34 | @ifset H8/500 |
| 35 | @set H8 |
| 36 | @end ifset |
| 37 | @ifset SH |
| 38 | @set H8 |
| 39 | @end ifset |
| 40 | @ifset HPPA |
| 41 | @set abnormal-separator |
| 42 | @end ifset |
| 43 | @c ------------ |
| 44 | @ifset GENERIC |
| 45 | @settitle Using @value{AS} |
| 46 | @end ifset |
| 47 | @ifclear GENERIC |
| 48 | @settitle Using @value{AS} (@value{TARGET}) |
| 49 | @end ifclear |
| 50 | @setchapternewpage odd |
| 51 | @c %**end of header |
| 52 | |
| 53 | @c @smallbook |
| 54 | @c @set SMALL |
| 55 | @c WARE! Some of the machine-dependent sections contain tables of machine |
| 56 | @c instructions. Except in multi-column format, these tables look silly. |
| 57 | @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so |
| 58 | @c the multi-col format is faked within @example sections. |
| 59 | @c |
| 60 | @c Again unfortunately, the natural size that fits on a page, for these tables, |
| 61 | @c is different depending on whether or not smallbook is turned on. |
| 62 | @c This matters, because of order: text flow switches columns at each page |
| 63 | @c break. |
| 64 | @c |
| 65 | @c The format faked in this source works reasonably well for smallbook, |
| 66 | @c not well for the default large-page format. This manual expects that if you |
| 67 | @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the |
| 68 | @c tables in question. You can turn on one without the other at your |
| 69 | @c discretion, of course. |
| 70 | @ifinfo |
| 71 | @set SMALL |
| 72 | @c the insn tables look just as silly in info files regardless of smallbook, |
| 73 | @c might as well show 'em anyways. |
| 74 | @end ifinfo |
| 75 | |
| 76 | @ifinfo |
| 77 | @format |
| 78 | START-INFO-DIR-ENTRY |
| 79 | * As: (as). The GNU assembler. |
| 80 | END-INFO-DIR-ENTRY |
| 81 | @end format |
| 82 | @end ifinfo |
| 83 | |
| 84 | @finalout |
| 85 | @syncodeindex ky cp |
| 86 | |
| 87 | @ifinfo |
| 88 | This file documents the GNU Assembler "@value{AS}". |
| 89 | |
| 90 | Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc. |
| 91 | |
| 92 | Permission is granted to make and distribute verbatim copies of |
| 93 | this manual provided the copyright notice and this permission notice |
| 94 | are preserved on all copies. |
| 95 | |
| 96 | @ignore |
| 97 | Permission is granted to process this file through Tex and print the |
| 98 | results, provided the printed document carries copying permission |
| 99 | notice identical to this one except for the removal of this paragraph |
| 100 | (this paragraph not being relevant to the printed manual). |
| 101 | |
| 102 | @end ignore |
| 103 | Permission is granted to copy and distribute modified versions of this manual |
| 104 | under the conditions for verbatim copying, provided that the entire resulting |
| 105 | derived work is distributed under the terms of a permission notice identical to |
| 106 | this one. |
| 107 | |
| 108 | Permission is granted to copy and distribute translations of this manual |
| 109 | into another language, under the above conditions for modified versions. |
| 110 | @end ifinfo |
| 111 | |
| 112 | @titlepage |
| 113 | @title Using @value{AS} |
| 114 | @subtitle The @sc{gnu} Assembler |
| 115 | @ifclear GENERIC |
| 116 | @subtitle for the @value{TARGET} family |
| 117 | @end ifclear |
| 118 | @sp 1 |
| 119 | @subtitle Version @value{VERSION} |
| 120 | @sp 1 |
| 121 | @sp 13 |
| 122 | The Free Software Foundation Inc. thanks The Nice Computer |
| 123 | Company of Australia for loaning Dean Elsner to write the |
| 124 | first (Vax) version of @code{as} for Project @sc{gnu}. |
| 125 | The proprietors, management and staff of TNCCA thank FSF for |
| 126 | distracting the boss while they got some work |
| 127 | done. |
| 128 | @sp 3 |
| 129 | @author Dean Elsner, Jay Fenlason & friends |
| 130 | @page |
| 131 | @tex |
| 132 | {\parskip=0pt |
| 133 | \hfill {\it Using {\tt @value{AS}}}\par |
| 134 | \hfill Edited by Cygnus Support\par |
| 135 | } |
| 136 | %"boxit" macro for figures: |
| 137 | %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3) |
| 138 | \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt |
| 139 | \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil |
| 140 | #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline |
| 141 | \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box |
| 142 | @end tex |
| 143 | |
| 144 | @vskip 0pt plus 1filll |
| 145 | Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc. |
| 146 | |
| 147 | Permission is granted to make and distribute verbatim copies of |
| 148 | this manual provided the copyright notice and this permission notice |
| 149 | are preserved on all copies. |
| 150 | |
| 151 | Permission is granted to copy and distribute modified versions of this manual |
| 152 | under the conditions for verbatim copying, provided that the entire resulting |
| 153 | derived work is distributed under the terms of a permission notice identical to |
| 154 | this one. |
| 155 | |
| 156 | Permission is granted to copy and distribute translations of this manual |
| 157 | into another language, under the above conditions for modified versions. |
| 158 | @end titlepage |
| 159 | |
| 160 | @ifinfo |
| 161 | @node Top |
| 162 | @top Using @value{AS} |
| 163 | |
| 164 | This file is a user guide to the @sc{gnu} assembler @code{@value{AS}} version |
| 165 | @value{VERSION}. |
| 166 | @ifclear GENERIC |
| 167 | This version of the file describes @code{@value{AS}} configured to generate |
| 168 | code for @value{TARGET} architectures. |
| 169 | @end ifclear |
| 170 | @menu |
| 171 | * Overview:: Overview |
| 172 | * Invoking:: Command-Line Options |
| 173 | * Syntax:: Syntax |
| 174 | * Sections:: Sections and Relocation |
| 175 | * Symbols:: Symbols |
| 176 | * Expressions:: Expressions |
| 177 | * Pseudo Ops:: Assembler Directives |
| 178 | * Machine Dependencies:: Machine Dependent Features |
| 179 | * Reporting Bugs:: Reporting Bugs |
| 180 | * Acknowledgements:: Who Did What |
| 181 | * Index:: Index |
| 182 | @end menu |
| 183 | @end ifinfo |
| 184 | |
| 185 | @node Overview |
| 186 | @chapter Overview |
| 187 | @iftex |
| 188 | This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}. |
| 189 | @ifclear GENERIC |
| 190 | This version of the manual describes @code{@value{AS}} configured to generate |
| 191 | code for @value{TARGET} architectures. |
| 192 | @end ifclear |
| 193 | @end iftex |
| 194 | |
| 195 | @cindex invocation summary |
| 196 | @cindex option summary |
| 197 | @cindex summary of options |
| 198 | Here is a brief summary of how to invoke @code{@value{AS}}. For details, |
| 199 | @pxref{Invoking,,Comand-Line Options}. |
| 200 | |
| 201 | @c We don't use deffn and friends for the following because they seem |
| 202 | @c to be limited to one line for the header. |
| 203 | @smallexample |
| 204 | @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ] |
| 205 | [ -f ] [ --gstabs ] [ --gdwarf2 ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ] |
| 206 | [ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ] |
| 207 | [ -version ] [ --version ] [ -W ] [ --warn ] [ --fatal-warnings ] |
| 208 | [ -w ] [ -x ] [ -Z ] |
| 209 | @ifset A29K |
| 210 | @c am29k has no machine-dependent assembler options |
| 211 | @end ifset |
| 212 | @ifset ARC |
| 213 | [ -mbig-endian | -mlittle-endian ] |
| 214 | @end ifset |
| 215 | @ifset ARM |
| 216 | [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]60 | |
| 217 | -m[arm]600 | -m[arm]610 | -m[arm]620 | -m[arm]7[t][[d]m[i]][fe] | -m[arm]70 | |
| 218 | -m[arm]700 | -m[arm]710[c] | -m[arm]7100 | -m[arm]7500 | -m[arm]8 | |
| 219 | -m[arm]810 | -m[arm]9 | -m[arm]920 | -m[arm]920t | -m[arm]9tdmi | |
| 220 | -mstrongarm | -mstrongarm110 | -mstrongarm1100 ] |
| 221 | [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t | |
| 222 | -m[arm]v5 | -[arm]v5t ] |
| 223 | [ -mthumb | -mall ] |
| 224 | [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ] |
| 225 | [ -EB | -EL ] |
| 226 | [ -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant ] |
| 227 | [ -mthumb-interwork ] |
| 228 | [ -moabi ] |
| 229 | [ -k ] |
| 230 | @end ifset |
| 231 | @ifset D10V |
| 232 | [ -O ] |
| 233 | @end ifset |
| 234 | @ifset D30V |
| 235 | [ -O | -n | -N ] |
| 236 | @end ifset |
| 237 | @ifset H8 |
| 238 | @c Hitachi family chips have no machine-dependent assembler options |
| 239 | @end ifset |
| 240 | @ifset HPPA |
| 241 | @c HPPA has no machine-dependent assembler options (yet). |
| 242 | @end ifset |
| 243 | @ifset PJ |
| 244 | [ -mb | -me ] |
| 245 | @end ifset |
| 246 | @ifset SPARC |
| 247 | @c The order here is important. See c-sparc.texi. |
| 248 | [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite |
| 249 | -Av8plus | -Av8plusa | -Av9 | -Av9a ] |
| 250 | [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ] |
| 251 | @end ifset |
| 252 | @ifset Z8000 |
| 253 | @c Z8000 has no machine-dependent assembler options |
| 254 | @end ifset |
| 255 | @ifset I960 |
| 256 | @c see md_parse_option in tc-i960.c |
| 257 | [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ] |
| 258 | [ -b ] [ -no-relax ] |
| 259 | @end ifset |
| 260 | @ifset M680X0 |
| 261 | [ -l ] [ -m68000 | -m68010 | -m68020 | ... ] |
| 262 | @end ifset |
| 263 | @ifset MCORE |
| 264 | [ -jsri2bsr ] [ -sifilter ] [ -relax ] |
| 265 | @end ifset |
| 266 | @ifset MIPS |
| 267 | [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ] |
| 268 | [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ] |
| 269 | [ --trap ] [ --break ] |
| 270 | [ --emulation=@var{name} ] |
| 271 | @end ifset |
| 272 | [ -- | @var{files} @dots{} ] |
| 273 | @end smallexample |
| 274 | |
| 275 | @table @code |
| 276 | @item -a[cdhlmns] |
| 277 | Turn on listings, in any of a variety of ways: |
| 278 | |
| 279 | @table @code |
| 280 | @item -ac |
| 281 | omit false conditionals |
| 282 | |
| 283 | @item -ad |
| 284 | omit debugging directives |
| 285 | |
| 286 | @item -ah |
| 287 | include high-level source |
| 288 | |
| 289 | @item -al |
| 290 | include assembly |
| 291 | |
| 292 | @item -am |
| 293 | include macro expansions |
| 294 | |
| 295 | @item -an |
| 296 | omit forms processing |
| 297 | |
| 298 | @item -as |
| 299 | include symbols |
| 300 | |
| 301 | @item =file |
| 302 | set the name of the listing file |
| 303 | @end table |
| 304 | |
| 305 | You may combine these options; for example, use @samp{-aln} for assembly |
| 306 | listing without forms processing. The @samp{=file} option, if used, must be |
| 307 | the last one. By itself, @samp{-a} defaults to @samp{-ahls}. |
| 308 | |
| 309 | @item -D |
| 310 | Ignored. This option is accepted for script compatibility with calls to |
| 311 | other assemblers. |
| 312 | |
| 313 | @item --defsym @var{sym}=@var{value} |
| 314 | Define the symbol @var{sym} to be @var{value} before assembling the input file. |
| 315 | @var{value} must be an integer constant. As in C, a leading @samp{0x} |
| 316 | indicates a hexadecimal value, and a leading @samp{0} indicates an octal value. |
| 317 | |
| 318 | @item -f |
| 319 | ``fast''---skip whitespace and comment preprocessing (assume source is |
| 320 | compiler output). |
| 321 | |
| 322 | @item --gstabs |
| 323 | Generate stabs debugging information for each assembler line. This |
| 324 | may help debugging assembler code, if the debugger can handle it. |
| 325 | |
| 326 | @item --gdwarf2 |
| 327 | Generate DWARF2 debugging information for each assembler line. This |
| 328 | may help debugging assembler code, if the debugger can handle it. |
| 329 | |
| 330 | @item --help |
| 331 | Print a summary of the command line options and exit. |
| 332 | |
| 333 | @item -I @var{dir} |
| 334 | Add directory @var{dir} to the search list for @code{.include} directives. |
| 335 | |
| 336 | @item -J |
| 337 | Don't warn about signed overflow. |
| 338 | |
| 339 | @item -K |
| 340 | @ifclear DIFF-TBL-KLUGE |
| 341 | This option is accepted but has no effect on the @value{TARGET} family. |
| 342 | @end ifclear |
| 343 | @ifset DIFF-TBL-KLUGE |
| 344 | Issue warnings when difference tables altered for long displacements. |
| 345 | @end ifset |
| 346 | |
| 347 | @item -L |
| 348 | @itemx --keep-locals |
| 349 | Keep (in the symbol table) local symbols. On traditional a.out systems |
| 350 | these start with @samp{L}, but different systems have different local |
| 351 | label prefixes. |
| 352 | |
| 353 | @item -o @var{objfile} |
| 354 | Name the object-file output from @code{@value{AS}} @var{objfile}. |
| 355 | |
| 356 | @item -R |
| 357 | Fold the data section into the text section. |
| 358 | |
| 359 | @item --statistics |
| 360 | Print the maximum space (in bytes) and total time (in seconds) used by |
| 361 | assembly. |
| 362 | |
| 363 | @item --strip-local-absolute |
| 364 | Remove local absolute symbols from the outgoing symbol table. |
| 365 | |
| 366 | @item -v |
| 367 | @itemx -version |
| 368 | Print the @code{as} version. |
| 369 | |
| 370 | @item --version |
| 371 | Print the @code{as} version and exit. |
| 372 | |
| 373 | @item -W |
| 374 | @itemx --no-warn |
| 375 | Suppress warning messages. |
| 376 | |
| 377 | @item --fatal-warnings |
| 378 | Treat warnings as errors. |
| 379 | |
| 380 | @item --warn |
| 381 | Don't suppress warning messages or treat them as errors. |
| 382 | |
| 383 | @item -w |
| 384 | Ignored. |
| 385 | |
| 386 | @item -x |
| 387 | Ignored. |
| 388 | |
| 389 | @item -Z |
| 390 | Generate an object file even after errors. |
| 391 | |
| 392 | @item -- | @var{files} @dots{} |
| 393 | Standard input, or source files to assemble. |
| 394 | |
| 395 | @end table |
| 396 | |
| 397 | @ifset ARC |
| 398 | The following options are available when @value{AS} is configured for |
| 399 | an ARC processor. |
| 400 | |
| 401 | @table @code |
| 402 | |
| 403 | @cindex ARC endianness |
| 404 | @cindex endianness, ARC |
| 405 | @cindex big endian output, ARC |
| 406 | @item -mbig-endian |
| 407 | Generate ``big endian'' format output. |
| 408 | |
| 409 | @cindex little endian output, ARC |
| 410 | @item -mlittle-endian |
| 411 | Generate ``little endian'' format output. |
| 412 | |
| 413 | @end table |
| 414 | @end ifset |
| 415 | |
| 416 | @ifset ARM |
| 417 | The following options are available when @value{AS} is configured for the ARM |
| 418 | processor family. |
| 419 | |
| 420 | @table @code |
| 421 | @item -m[arm][1|2|3|6|7|8|9][...] |
| 422 | Specify which ARM processor variant is the target. |
| 423 | @item -m[arm]v[2|2a|3|3m|4|4t|5|5t] |
| 424 | Specify which ARM architecture variant is used by the target. |
| 425 | @item -mthumb | -mall |
| 426 | Enable or disable Thumb only instruction decoding. |
| 427 | @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu |
| 428 | Select which Floating Point architcture is the target. |
| 429 | @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi |
| 430 | Select which procedure calling convention is in use. |
| 431 | @item -EB | -EL |
| 432 | Select either big-endian (-EB) or little-endian (-EL) output. |
| 433 | @item -mthumb-interwork |
| 434 | Specify that the code has been generated with interworking between Thumb and |
| 435 | ARM code in mind. |
| 436 | @item -k |
| 437 | Specify that PIC code has been generated. |
| 438 | @end table |
| 439 | @end ifset |
| 440 | |
| 441 | @ifset D10V |
| 442 | The following options are available when @value{AS} is configured for |
| 443 | a D10V processor. |
| 444 | @table @code |
| 445 | @cindex D10V optimization |
| 446 | @cindex optimization, D10V |
| 447 | @item -O |
| 448 | Optimize output by parallelizing instructions. |
| 449 | @end table |
| 450 | @end ifset |
| 451 | |
| 452 | @ifset D30V |
| 453 | The following options are available when @value{AS} is configured for a D30V |
| 454 | processor. |
| 455 | @table @code |
| 456 | @cindex D30V optimization |
| 457 | @cindex optimization, D30V |
| 458 | @item -O |
| 459 | Optimize output by parallelizing instructions. |
| 460 | |
| 461 | @cindex D30V nops |
| 462 | @item -n |
| 463 | Warn when nops are generated. |
| 464 | |
| 465 | @cindex D30V nops after 32-bit multiply |
| 466 | @item -N |
| 467 | Warn when a nop after a 32-bit multiply instruction is generated. |
| 468 | @end table |
| 469 | @end ifset |
| 470 | |
| 471 | @ifset I960 |
| 472 | The following options are available when @value{AS} is configured for the |
| 473 | Intel 80960 processor. |
| 474 | |
| 475 | @table @code |
| 476 | @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC |
| 477 | Specify which variant of the 960 architecture is the target. |
| 478 | |
| 479 | @item -b |
| 480 | Add code to collect statistics about branches taken. |
| 481 | |
| 482 | @item -no-relax |
| 483 | Do not alter compare-and-branch instructions for long displacements; |
| 484 | error if necessary. |
| 485 | |
| 486 | @end table |
| 487 | @end ifset |
| 488 | |
| 489 | |
| 490 | @ifset M680X0 |
| 491 | The following options are available when @value{AS} is configured for the |
| 492 | Motorola 68000 series. |
| 493 | |
| 494 | @table @code |
| 495 | |
| 496 | @item -l |
| 497 | Shorten references to undefined symbols, to one word instead of two. |
| 498 | |
| 499 | @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060 |
| 500 | @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200 |
| 501 | Specify what processor in the 68000 family is the target. The default |
| 502 | is normally the 68020, but this can be changed at configuration time. |
| 503 | |
| 504 | @item -m68881 | -m68882 | -mno-68881 | -mno-68882 |
| 505 | The target machine does (or does not) have a floating-point coprocessor. |
| 506 | The default is to assume a coprocessor for 68020, 68030, and cpu32. Although |
| 507 | the basic 68000 is not compatible with the 68881, a combination of the |
| 508 | two can be specified, since it's possible to do emulation of the |
| 509 | coprocessor instructions with the main processor. |
| 510 | |
| 511 | @item -m68851 | -mno-68851 |
| 512 | The target machine does (or does not) have a memory-management |
| 513 | unit coprocessor. The default is to assume an MMU for 68020 and up. |
| 514 | |
| 515 | @end table |
| 516 | @end ifset |
| 517 | |
| 518 | @ifset PJ |
| 519 | The following options are available when @value{AS} is configured for |
| 520 | a picoJava processor. |
| 521 | |
| 522 | @table @code |
| 523 | |
| 524 | @cindex PJ endianness |
| 525 | @cindex endianness, PJ |
| 526 | @cindex big endian output, PJ |
| 527 | @item -mb |
| 528 | Generate ``big endian'' format output. |
| 529 | |
| 530 | @cindex little endian output, PJ |
| 531 | @item -ml |
| 532 | Generate ``little endian'' format output. |
| 533 | |
| 534 | @end table |
| 535 | @end ifset |
| 536 | |
| 537 | |
| 538 | @ifset SPARC |
| 539 | The following options are available when @code{@value{AS}} is configured |
| 540 | for the SPARC architecture: |
| 541 | |
| 542 | @table @code |
| 543 | @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite |
| 544 | @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a |
| 545 | Explicitly select a variant of the SPARC architecture. |
| 546 | |
| 547 | @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment. |
| 548 | @samp{-Av9} and @samp{-Av9a} select a 64 bit environment. |
| 549 | |
| 550 | @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with |
| 551 | UltraSPARC extensions. |
| 552 | |
| 553 | @item -xarch=v8plus | -xarch=v8plusa |
| 554 | For compatibility with the Solaris v9 assembler. These options are |
| 555 | equivalent to -Av8plus and -Av8plusa, respectively. |
| 556 | |
| 557 | @item -bump |
| 558 | Warn when the assembler switches to another architecture. |
| 559 | @end table |
| 560 | @end ifset |
| 561 | |
| 562 | @ifset MIPS |
| 563 | The following options are available when @value{AS} is configured for |
| 564 | a MIPS processor. |
| 565 | |
| 566 | @table @code |
| 567 | @item -G @var{num} |
| 568 | This option sets the largest size of an object that can be referenced |
| 569 | implicitly with the @code{gp} register. It is only accepted for targets that |
| 570 | use ECOFF format, such as a DECstation running Ultrix. The default value is 8. |
| 571 | |
| 572 | @cindex MIPS endianness |
| 573 | @cindex endianness, MIPS |
| 574 | @cindex big endian output, MIPS |
| 575 | @item -EB |
| 576 | Generate ``big endian'' format output. |
| 577 | |
| 578 | @cindex little endian output, MIPS |
| 579 | @item -EL |
| 580 | Generate ``little endian'' format output. |
| 581 | |
| 582 | @cindex MIPS ISA |
| 583 | @item -mips1 |
| 584 | @itemx -mips2 |
| 585 | @itemx -mips3 |
| 586 | Generate code for a particular MIPS Instruction Set Architecture level. |
| 587 | @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors, |
| 588 | @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000} |
| 589 | processor. |
| 590 | |
| 591 | @item -m4650 |
| 592 | @itemx -no-m4650 |
| 593 | Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept |
| 594 | the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop} |
| 595 | instructions around accesses to the @samp{HI} and @samp{LO} registers. |
| 596 | @samp{-no-m4650} turns off this option. |
| 597 | |
| 598 | @item -mcpu=@var{CPU} |
| 599 | Generate code for a particular MIPS cpu. This has little effect on the |
| 600 | assembler, but it is passed by @code{@value{GCC}}. |
| 601 | |
| 602 | @cindex emulation |
| 603 | @item --emulation=@var{name} |
| 604 | This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured |
| 605 | for some other target, in all respects, including output format (choosing |
| 606 | between ELF and ECOFF only), handling of pseudo-opcodes which may generate |
| 607 | debugging information or store symbol table information, and default |
| 608 | endianness. The available configuration names are: @samp{mipsecoff}, |
| 609 | @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf}, |
| 610 | @samp{mipsbelf}. The first two do not alter the default endianness from that |
| 611 | of the primary target for which the assembler was configured; the others change |
| 612 | the default to little- or big-endian as indicated by the @samp{b} or @samp{l} |
| 613 | in the name. Using @samp{-EB} or @samp{-EL} will override the endianness |
| 614 | selection in any case. |
| 615 | |
| 616 | This option is currently supported only when the primary target |
| 617 | @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target. |
| 618 | Furthermore, the primary target or others specified with |
| 619 | @samp{--enable-targets=@dots{}} at configuration time must include support for |
| 620 | the other format, if both are to be available. For example, the Irix 5 |
| 621 | configuration includes support for both. |
| 622 | |
| 623 | Eventually, this option will support more configurations, with more |
| 624 | fine-grained control over the assembler's behavior, and will be supported for |
| 625 | more processors. |
| 626 | |
| 627 | @item -nocpp |
| 628 | @code{@value{AS}} ignores this option. It is accepted for compatibility with |
| 629 | the native tools. |
| 630 | |
| 631 | @need 900 |
| 632 | @item --trap |
| 633 | @itemx --no-trap |
| 634 | @itemx --break |
| 635 | @itemx --no-break |
| 636 | Control how to deal with multiplication overflow and division by zero. |
| 637 | @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception |
| 638 | (and only work for Instruction Set Architecture level 2 and higher); |
| 639 | @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a |
| 640 | break exception. |
| 641 | @end table |
| 642 | @end ifset |
| 643 | |
| 644 | @ifset MCORE |
| 645 | The following options are available when @value{AS} is configured for |
| 646 | an MCore processor. |
| 647 | |
| 648 | @table @code |
| 649 | @item -jsri2bsr |
| 650 | @itemx -nojsri2bsr |
| 651 | Enable or disable the JSRI to BSR transformation. By default this is enabled. |
| 652 | The command line option @samp{-nojsri2bsr} can be used to disable it. |
| 653 | |
| 654 | @item -sifilter |
| 655 | @itemx -nosifilter |
| 656 | Enable or disable the silicon filter behaviour. By default this is disabled. |
| 657 | The default can be overidden by the @samp{-sifilter} command line option. |
| 658 | |
| 659 | @item -relax |
| 660 | Alter jump instructions for long displacements. |
| 661 | |
| 662 | |
| 663 | @end table |
| 664 | @end ifset |
| 665 | |
| 666 | @menu |
| 667 | * Manual:: Structure of this Manual |
| 668 | * GNU Assembler:: The GNU Assembler |
| 669 | * Object Formats:: Object File Formats |
| 670 | * Command Line:: Command Line |
| 671 | * Input Files:: Input Files |
| 672 | * Object:: Output (Object) File |
| 673 | * Errors:: Error and Warning Messages |
| 674 | @end menu |
| 675 | |
| 676 | @node Manual |
| 677 | @section Structure of this Manual |
| 678 | |
| 679 | @cindex manual, structure and purpose |
| 680 | This manual is intended to describe what you need to know to use |
| 681 | @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including |
| 682 | notation for symbols, constants, and expressions; the directives that |
| 683 | @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}. |
| 684 | |
| 685 | @ifclear GENERIC |
| 686 | We also cover special features in the @value{TARGET} |
| 687 | configuration of @code{@value{AS}}, including assembler directives. |
| 688 | @end ifclear |
| 689 | @ifset GENERIC |
| 690 | This manual also describes some of the machine-dependent features of |
| 691 | various flavors of the assembler. |
| 692 | @end ifset |
| 693 | |
| 694 | @cindex machine instructions (not covered) |
| 695 | On the other hand, this manual is @emph{not} intended as an introduction |
| 696 | to programming in assembly language---let alone programming in general! |
| 697 | In a similar vein, we make no attempt to introduce the machine |
| 698 | architecture; we do @emph{not} describe the instruction set, standard |
| 699 | mnemonics, registers or addressing modes that are standard to a |
| 700 | particular architecture. |
| 701 | @ifset GENERIC |
| 702 | You may want to consult the manufacturer's |
| 703 | machine architecture manual for this information. |
| 704 | @end ifset |
| 705 | @ifclear GENERIC |
| 706 | @ifset H8/300 |
| 707 | For information on the H8/300 machine instruction set, see @cite{H8/300 |
| 708 | Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H, |
| 709 | see @cite{H8/300H Series Programming Manual} (Hitachi). |
| 710 | @end ifset |
| 711 | @ifset H8/500 |
| 712 | For information on the H8/500 machine instruction set, see @cite{H8/500 |
| 713 | Series Programming Manual} (Hitachi M21T001). |
| 714 | @end ifset |
| 715 | @ifset SH |
| 716 | For information on the Hitachi SH machine instruction set, see |
| 717 | @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.). |
| 718 | @end ifset |
| 719 | @ifset Z8000 |
| 720 | For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual} |
| 721 | @end ifset |
| 722 | @end ifclear |
| 723 | |
| 724 | @c I think this is premature---doc@cygnus.com, 17jan1991 |
| 725 | @ignore |
| 726 | Throughout this manual, we assume that you are running @dfn{GNU}, |
| 727 | the portable operating system from the @dfn{Free Software |
| 728 | Foundation, Inc.}. This restricts our attention to certain kinds of |
| 729 | computer (in particular, the kinds of computers that @sc{gnu} can run on); |
| 730 | once this assumption is granted examples and definitions need less |
| 731 | qualification. |
| 732 | |
| 733 | @code{@value{AS}} is part of a team of programs that turn a high-level |
| 734 | human-readable series of instructions into a low-level |
| 735 | computer-readable series of instructions. Different versions of |
| 736 | @code{@value{AS}} are used for different kinds of computer. |
| 737 | @end ignore |
| 738 | |
| 739 | @c There used to be a section "Terminology" here, which defined |
| 740 | @c "contents", "byte", "word", and "long". Defining "word" to any |
| 741 | @c particular size is confusing when the .word directive may generate 16 |
| 742 | @c bits on one machine and 32 bits on another; in general, for the user |
| 743 | @c version of this manual, none of these terms seem essential to define. |
| 744 | @c They were used very little even in the former draft of the manual; |
| 745 | @c this draft makes an effort to avoid them (except in names of |
| 746 | @c directives). |
| 747 | |
| 748 | @node GNU Assembler |
| 749 | @section The GNU Assembler |
| 750 | |
| 751 | @sc{gnu} @code{as} is really a family of assemblers. |
| 752 | @ifclear GENERIC |
| 753 | This manual describes @code{@value{AS}}, a member of that family which is |
| 754 | configured for the @value{TARGET} architectures. |
| 755 | @end ifclear |
| 756 | If you use (or have used) the @sc{gnu} assembler on one architecture, you |
| 757 | should find a fairly similar environment when you use it on another |
| 758 | architecture. Each version has much in common with the others, |
| 759 | including object file formats, most assembler directives (often called |
| 760 | @dfn{pseudo-ops}) and assembler syntax.@refill |
| 761 | |
| 762 | @cindex purpose of @sc{gnu} assembler |
| 763 | @code{@value{AS}} is primarily intended to assemble the output of the |
| 764 | @sc{gnu} C compiler @code{@value{GCC}} for use by the linker |
| 765 | @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}} |
| 766 | assemble correctly everything that other assemblers for the same |
| 767 | machine would assemble. |
| 768 | @ifset VAX |
| 769 | Any exceptions are documented explicitly (@pxref{Machine Dependencies}). |
| 770 | @end ifset |
| 771 | @ifset M680X0 |
| 772 | @c This remark should appear in generic version of manual; assumption |
| 773 | @c here is that generic version sets M680x0. |
| 774 | This doesn't mean @code{@value{AS}} always uses the same syntax as another |
| 775 | assembler for the same architecture; for example, we know of several |
| 776 | incompatible versions of 680x0 assembly language syntax. |
| 777 | @end ifset |
| 778 | |
| 779 | Unlike older assemblers, @code{@value{AS}} is designed to assemble a source |
| 780 | program in one pass of the source file. This has a subtle impact on the |
| 781 | @kbd{.org} directive (@pxref{Org,,@code{.org}}). |
| 782 | |
| 783 | @node Object Formats |
| 784 | @section Object File Formats |
| 785 | |
| 786 | @cindex object file format |
| 787 | The @sc{gnu} assembler can be configured to produce several alternative |
| 788 | object file formats. For the most part, this does not affect how you |
| 789 | write assembly language programs; but directives for debugging symbols |
| 790 | are typically different in different file formats. @xref{Symbol |
| 791 | Attributes,,Symbol Attributes}. |
| 792 | @ifclear GENERIC |
| 793 | @ifclear MULTI-OBJ |
| 794 | On the @value{TARGET}, @code{@value{AS}} is configured to produce |
| 795 | @value{OBJ-NAME} format object files. |
| 796 | @end ifclear |
| 797 | @c The following should exhaust all configs that set MULTI-OBJ, ideally |
| 798 | @ifset A29K |
| 799 | On the @value{TARGET}, @code{@value{AS}} can be configured to produce either |
| 800 | @code{a.out} or COFF format object files. |
| 801 | @end ifset |
| 802 | @ifset I960 |
| 803 | On the @value{TARGET}, @code{@value{AS}} can be configured to produce either |
| 804 | @code{b.out} or COFF format object files. |
| 805 | @end ifset |
| 806 | @ifset HPPA |
| 807 | On the @value{TARGET}, @code{@value{AS}} can be configured to produce either |
| 808 | SOM or ELF format object files. |
| 809 | @end ifset |
| 810 | @end ifclear |
| 811 | |
| 812 | @node Command Line |
| 813 | @section Command Line |
| 814 | |
| 815 | @cindex command line conventions |
| 816 | After the program name @code{@value{AS}}, the command line may contain |
| 817 | options and file names. Options may appear in any order, and may be |
| 818 | before, after, or between file names. The order of file names is |
| 819 | significant. |
| 820 | |
| 821 | @cindex standard input, as input file |
| 822 | @kindex -- |
| 823 | @file{--} (two hyphens) by itself names the standard input file |
| 824 | explicitly, as one of the files for @code{@value{AS}} to assemble. |
| 825 | |
| 826 | @cindex options, command line |
| 827 | Except for @samp{--} any command line argument that begins with a |
| 828 | hyphen (@samp{-}) is an option. Each option changes the behavior of |
| 829 | @code{@value{AS}}. No option changes the way another option works. An |
| 830 | option is a @samp{-} followed by one or more letters; the case of |
| 831 | the letter is important. All options are optional. |
| 832 | |
| 833 | Some options expect exactly one file name to follow them. The file |
| 834 | name may either immediately follow the option's letter (compatible |
| 835 | with older assemblers) or it may be the next command argument (@sc{gnu} |
| 836 | standard). These two command lines are equivalent: |
| 837 | |
| 838 | @smallexample |
| 839 | @value{AS} -o my-object-file.o mumble.s |
| 840 | @value{AS} -omy-object-file.o mumble.s |
| 841 | @end smallexample |
| 842 | |
| 843 | @node Input Files |
| 844 | @section Input Files |
| 845 | |
| 846 | @cindex input |
| 847 | @cindex source program |
| 848 | @cindex files, input |
| 849 | We use the phrase @dfn{source program}, abbreviated @dfn{source}, to |
| 850 | describe the program input to one run of @code{@value{AS}}. The program may |
| 851 | be in one or more files; how the source is partitioned into files |
| 852 | doesn't change the meaning of the source. |
| 853 | |
| 854 | @c I added "con" prefix to "catenation" just to prove I can overcome my |
| 855 | @c APL training... doc@cygnus.com |
| 856 | The source program is a concatenation of the text in all the files, in the |
| 857 | order specified. |
| 858 | |
| 859 | Each time you run @code{@value{AS}} it assembles exactly one source |
| 860 | program. The source program is made up of one or more files. |
| 861 | (The standard input is also a file.) |
| 862 | |
| 863 | You give @code{@value{AS}} a command line that has zero or more input file |
| 864 | names. The input files are read (from left file name to right). A |
| 865 | command line argument (in any position) that has no special meaning |
| 866 | is taken to be an input file name. |
| 867 | |
| 868 | If you give @code{@value{AS}} no file names it attempts to read one input file |
| 869 | from the @code{@value{AS}} standard input, which is normally your terminal. You |
| 870 | may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program |
| 871 | to assemble. |
| 872 | |
| 873 | Use @samp{--} if you need to explicitly name the standard input file |
| 874 | in your command line. |
| 875 | |
| 876 | If the source is empty, @code{@value{AS}} produces a small, empty object |
| 877 | file. |
| 878 | |
| 879 | @subheading Filenames and Line-numbers |
| 880 | |
| 881 | @cindex input file linenumbers |
| 882 | @cindex line numbers, in input files |
| 883 | There are two ways of locating a line in the input file (or files) and |
| 884 | either may be used in reporting error messages. One way refers to a line |
| 885 | number in a physical file; the other refers to a line number in a |
| 886 | ``logical'' file. @xref{Errors, ,Error and Warning Messages}. |
| 887 | |
| 888 | @dfn{Physical files} are those files named in the command line given |
| 889 | to @code{@value{AS}}. |
| 890 | |
| 891 | @dfn{Logical files} are simply names declared explicitly by assembler |
| 892 | directives; they bear no relation to physical files. Logical file names help |
| 893 | error messages reflect the original source file, when @code{@value{AS}} source |
| 894 | is itself synthesized from other files. @code{@value{AS}} understands the |
| 895 | @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also |
| 896 | @ref{File,,@code{.file}}. |
| 897 | |
| 898 | @node Object |
| 899 | @section Output (Object) File |
| 900 | |
| 901 | @cindex object file |
| 902 | @cindex output file |
| 903 | @kindex a.out |
| 904 | @kindex .o |
| 905 | Every time you run @code{@value{AS}} it produces an output file, which is |
| 906 | your assembly language program translated into numbers. This file |
| 907 | is the object file. Its default name is |
| 908 | @ifclear BOUT |
| 909 | @code{a.out}. |
| 910 | @end ifclear |
| 911 | @ifset BOUT |
| 912 | @ifset GENERIC |
| 913 | @code{a.out}, or |
| 914 | @end ifset |
| 915 | @code{b.out} when @code{@value{AS}} is configured for the Intel 80960. |
| 916 | @end ifset |
| 917 | You can give it another name by using the @code{-o} option. Conventionally, |
| 918 | object file names end with @file{.o}. The default name is used for historical |
| 919 | reasons: older assemblers were capable of assembling self-contained programs |
| 920 | directly into a runnable program. (For some formats, this isn't currently |
| 921 | possible, but it can be done for the @code{a.out} format.) |
| 922 | |
| 923 | @cindex linker |
| 924 | @kindex ld |
| 925 | The object file is meant for input to the linker @code{@value{LD}}. It contains |
| 926 | assembled program code, information to help @code{@value{LD}} integrate |
| 927 | the assembled program into a runnable file, and (optionally) symbolic |
| 928 | information for the debugger. |
| 929 | |
| 930 | @c link above to some info file(s) like the description of a.out. |
| 931 | @c don't forget to describe @sc{gnu} info as well as Unix lossage. |
| 932 | |
| 933 | @node Errors |
| 934 | @section Error and Warning Messages |
| 935 | |
| 936 | @cindex error messsages |
| 937 | @cindex warning messages |
| 938 | @cindex messages from assembler |
| 939 | @code{@value{AS}} may write warnings and error messages to the standard error |
| 940 | file (usually your terminal). This should not happen when a compiler |
| 941 | runs @code{@value{AS}} automatically. Warnings report an assumption made so |
| 942 | that @code{@value{AS}} could keep assembling a flawed program; errors report a |
| 943 | grave problem that stops the assembly. |
| 944 | |
| 945 | @cindex format of warning messages |
| 946 | Warning messages have the format |
| 947 | |
| 948 | @smallexample |
| 949 | file_name:@b{NNN}:Warning Message Text |
| 950 | @end smallexample |
| 951 | |
| 952 | @noindent |
| 953 | @cindex line numbers, in warnings/errors |
| 954 | (where @b{NNN} is a line number). If a logical file name has been given |
| 955 | (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of |
| 956 | the current input file is used. If a logical line number was given |
| 957 | @ifset GENERIC |
| 958 | (@pxref{Line,,@code{.line}}) |
| 959 | @end ifset |
| 960 | @ifclear GENERIC |
| 961 | @ifclear A29K |
| 962 | (@pxref{Line,,@code{.line}}) |
| 963 | @end ifclear |
| 964 | @ifset A29K |
| 965 | (@pxref{Ln,,@code{.ln}}) |
| 966 | @end ifset |
| 967 | @end ifclear |
| 968 | then it is used to calculate the number printed, |
| 969 | otherwise the actual line in the current source file is printed. The |
| 970 | message text is intended to be self explanatory (in the grand Unix |
| 971 | tradition). |
| 972 | |
| 973 | @cindex format of error messages |
| 974 | Error messages have the format |
| 975 | @smallexample |
| 976 | file_name:@b{NNN}:FATAL:Error Message Text |
| 977 | @end smallexample |
| 978 | The file name and line number are derived as for warning |
| 979 | messages. The actual message text may be rather less explanatory |
| 980 | because many of them aren't supposed to happen. |
| 981 | |
| 982 | @node Invoking |
| 983 | @chapter Command-Line Options |
| 984 | |
| 985 | @cindex options, all versions of assembler |
| 986 | This chapter describes command-line options available in @emph{all} |
| 987 | versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific |
| 988 | @ifclear GENERIC |
| 989 | to the @value{TARGET}. |
| 990 | @end ifclear |
| 991 | @ifset GENERIC |
| 992 | to particular machine architectures. |
| 993 | @end ifset |
| 994 | |
| 995 | If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2), |
| 996 | you can use the @samp{-Wa} option to pass arguments through to the assembler. |
| 997 | The assembler arguments must be separated from each other (and the @samp{-Wa}) |
| 998 | by commas. For example: |
| 999 | |
| 1000 | @smallexample |
| 1001 | gcc -c -g -O -Wa,-alh,-L file.c |
| 1002 | @end smallexample |
| 1003 | |
| 1004 | @noindent |
| 1005 | This passes two options to the assembler: @samp{-alh} (emit a listing to |
| 1006 | standard output with with high-level and assembly source) and @samp{-L} (retain |
| 1007 | local symbols in the symbol table). |
| 1008 | |
| 1009 | Usually you do not need to use this @samp{-Wa} mechanism, since many compiler |
| 1010 | command-line options are automatically passed to the assembler by the compiler. |
| 1011 | (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see |
| 1012 | precisely what options it passes to each compilation pass, including the |
| 1013 | assembler.) |
| 1014 | |
| 1015 | @menu |
| 1016 | * a:: -a[cdhlns] enable listings |
| 1017 | * D:: -D for compatibility |
| 1018 | * f:: -f to work faster |
| 1019 | * I:: -I for .include search path |
| 1020 | @ifclear DIFF-TBL-KLUGE |
| 1021 | * K:: -K for compatibility |
| 1022 | @end ifclear |
| 1023 | @ifset DIFF-TBL-KLUGE |
| 1024 | * K:: -K for difference tables |
| 1025 | @end ifset |
| 1026 | |
| 1027 | * L:: -L to retain local labels |
| 1028 | * M:: -M or --mri to assemble in MRI compatibility mode |
| 1029 | * MD:: --MD for dependency tracking |
| 1030 | * o:: -o to name the object file |
| 1031 | * R:: -R to join data and text sections |
| 1032 | * statistics:: --statistics to see statistics about assembly |
| 1033 | * traditional-format:: --traditional-format for compatible output |
| 1034 | * v:: -v to announce version |
| 1035 | * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings |
| 1036 | * Z:: -Z to make object file even after errors |
| 1037 | @end menu |
| 1038 | |
| 1039 | @node a |
| 1040 | @section Enable Listings: @code{-a[cdhlns]} |
| 1041 | |
| 1042 | @kindex -a |
| 1043 | @kindex -ac |
| 1044 | @kindex -ad |
| 1045 | @kindex -ah |
| 1046 | @kindex -al |
| 1047 | @kindex -an |
| 1048 | @kindex -as |
| 1049 | @cindex listings, enabling |
| 1050 | @cindex assembly listings, enabling |
| 1051 | |
| 1052 | These options enable listing output from the assembler. By itself, |
| 1053 | @samp{-a} requests high-level, assembly, and symbols listing. |
| 1054 | You can use other letters to select specific options for the list: |
| 1055 | @samp{-ah} requests a high-level language listing, |
| 1056 | @samp{-al} requests an output-program assembly listing, and |
| 1057 | @samp{-as} requests a symbol table listing. |
| 1058 | High-level listings require that a compiler debugging option like |
| 1059 | @samp{-g} be used, and that assembly listings (@samp{-al}) be requested |
| 1060 | also. |
| 1061 | |
| 1062 | Use the @samp{-ac} option to omit false conditionals from a listing. Any lines |
| 1063 | which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any |
| 1064 | other conditional), or a true @code{.if} followed by an @code{.else}, will be |
| 1065 | omitted from the listing. |
| 1066 | |
| 1067 | Use the @samp{-ad} option to omit debugging directives from the |
| 1068 | listing. |
| 1069 | |
| 1070 | Once you have specified one of these options, you can further control |
| 1071 | listing output and its appearance using the directives @code{.list}, |
| 1072 | @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and |
| 1073 | @code{.sbttl}. |
| 1074 | The @samp{-an} option turns off all forms processing. |
| 1075 | If you do not request listing output with one of the @samp{-a} options, the |
| 1076 | listing-control directives have no effect. |
| 1077 | |
| 1078 | The letters after @samp{-a} may be combined into one option, |
| 1079 | @emph{e.g.}, @samp{-aln}. |
| 1080 | |
| 1081 | @node D |
| 1082 | @section @code{-D} |
| 1083 | |
| 1084 | @kindex -D |
| 1085 | This option has no effect whatsoever, but it is accepted to make it more |
| 1086 | likely that scripts written for other assemblers also work with |
| 1087 | @code{@value{AS}}. |
| 1088 | |
| 1089 | @node f |
| 1090 | @section Work Faster: @code{-f} |
| 1091 | |
| 1092 | @kindex -f |
| 1093 | @cindex trusted compiler |
| 1094 | @cindex faster processing (@code{-f}) |
| 1095 | @samp{-f} should only be used when assembling programs written by a |
| 1096 | (trusted) compiler. @samp{-f} stops the assembler from doing whitespace |
| 1097 | and comment preprocessing on |
| 1098 | the input file(s) before assembling them. @xref{Preprocessing, |
| 1099 | ,Preprocessing}. |
| 1100 | |
| 1101 | @quotation |
| 1102 | @emph{Warning:} if you use @samp{-f} when the files actually need to be |
| 1103 | preprocessed (if they contain comments, for example), @code{@value{AS}} does |
| 1104 | not work correctly. |
| 1105 | @end quotation |
| 1106 | |
| 1107 | @node I |
| 1108 | @section @code{.include} search path: @code{-I} @var{path} |
| 1109 | |
| 1110 | @kindex -I @var{path} |
| 1111 | @cindex paths for @code{.include} |
| 1112 | @cindex search path for @code{.include} |
| 1113 | @cindex @code{include} directive search path |
| 1114 | Use this option to add a @var{path} to the list of directories |
| 1115 | @code{@value{AS}} searches for files specified in @code{.include} |
| 1116 | directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as |
| 1117 | many times as necessary to include a variety of paths. The current |
| 1118 | working directory is always searched first; after that, @code{@value{AS}} |
| 1119 | searches any @samp{-I} directories in the same order as they were |
| 1120 | specified (left to right) on the command line. |
| 1121 | |
| 1122 | @node K |
| 1123 | @section Difference Tables: @code{-K} |
| 1124 | |
| 1125 | @kindex -K |
| 1126 | @ifclear DIFF-TBL-KLUGE |
| 1127 | On the @value{TARGET} family, this option is allowed, but has no effect. It is |
| 1128 | permitted for compatibility with the @sc{gnu} assembler on other platforms, |
| 1129 | where it can be used to warn when the assembler alters the machine code |
| 1130 | generated for @samp{.word} directives in difference tables. The @value{TARGET} |
| 1131 | family does not have the addressing limitations that sometimes lead to this |
| 1132 | alteration on other platforms. |
| 1133 | @end ifclear |
| 1134 | |
| 1135 | @ifset DIFF-TBL-KLUGE |
| 1136 | @cindex difference tables, warning |
| 1137 | @cindex warning for altered difference tables |
| 1138 | @code{@value{AS}} sometimes alters the code emitted for directives of the form |
| 1139 | @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}. |
| 1140 | You can use the @samp{-K} option if you want a warning issued when this |
| 1141 | is done. |
| 1142 | @end ifset |
| 1143 | |
| 1144 | @node L |
| 1145 | @section Include Local Labels: @code{-L} |
| 1146 | |
| 1147 | @kindex -L |
| 1148 | @cindex local labels, retaining in output |
| 1149 | Labels beginning with @samp{L} (upper case only) are called @dfn{local |
| 1150 | labels}. @xref{Symbol Names}. Normally you do not see such labels when |
| 1151 | debugging, because they are intended for the use of programs (like |
| 1152 | compilers) that compose assembler programs, not for your notice. |
| 1153 | Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not |
| 1154 | normally debug with them. |
| 1155 | |
| 1156 | This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols |
| 1157 | in the object file. Usually if you do this you also tell the linker |
| 1158 | @code{@value{LD}} to preserve symbols whose names begin with @samp{L}. |
| 1159 | |
| 1160 | By default, a local label is any label beginning with @samp{L}, but each |
| 1161 | target is allowed to redefine the local label prefix. |
| 1162 | @ifset HPPA |
| 1163 | On the HPPA local labels begin with @samp{L$}. |
| 1164 | @end ifset |
| 1165 | @ifset ARM |
| 1166 | @samp{;} for the ARM family; |
| 1167 | @end ifset |
| 1168 | |
| 1169 | @node M |
| 1170 | @section Assemble in MRI Compatibility Mode: @code{-M} |
| 1171 | |
| 1172 | @kindex -M |
| 1173 | @cindex MRI compatibility mode |
| 1174 | The @code{-M} or @code{--mri} option selects MRI compatibility mode. This |
| 1175 | changes the syntax and pseudo-op handling of @code{@value{AS}} to make it |
| 1176 | compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the |
| 1177 | configured target) assembler from Microtec Research. The exact nature of the |
| 1178 | MRI syntax will not be documented here; see the MRI manuals for more |
| 1179 | information. Note in particular that the handling of macros and macro |
| 1180 | arguments is somewhat different. The purpose of this option is to permit |
| 1181 | assembling existing MRI assembler code using @code{@value{AS}}. |
| 1182 | |
| 1183 | The MRI compatibility is not complete. Certain operations of the MRI assembler |
| 1184 | depend upon its object file format, and can not be supported using other object |
| 1185 | file formats. Supporting these would require enhancing each object file format |
| 1186 | individually. These are: |
| 1187 | |
| 1188 | @itemize @bullet |
| 1189 | @item global symbols in common section |
| 1190 | |
| 1191 | The m68k MRI assembler supports common sections which are merged by the linker. |
| 1192 | Other object file formats do not support this. @code{@value{AS}} handles |
| 1193 | common sections by treating them as a single common symbol. It permits local |
| 1194 | symbols to be defined within a common section, but it can not support global |
| 1195 | symbols, since it has no way to describe them. |
| 1196 | |
| 1197 | @item complex relocations |
| 1198 | |
| 1199 | The MRI assemblers support relocations against a negated section address, and |
| 1200 | relocations which combine the start addresses of two or more sections. These |
| 1201 | are not support by other object file formats. |
| 1202 | |
| 1203 | @item @code{END} pseudo-op specifying start address |
| 1204 | |
| 1205 | The MRI @code{END} pseudo-op permits the specification of a start address. |
| 1206 | This is not supported by other object file formats. The start address may |
| 1207 | instead be specified using the @code{-e} option to the linker, or in a linker |
| 1208 | script. |
| 1209 | |
| 1210 | @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops |
| 1211 | |
| 1212 | The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module |
| 1213 | name to the output file. This is not supported by other object file formats. |
| 1214 | |
| 1215 | @item @code{ORG} pseudo-op |
| 1216 | |
| 1217 | The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given |
| 1218 | address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op, |
| 1219 | which changes the location within the current section. Absolute sections are |
| 1220 | not supported by other object file formats. The address of a section may be |
| 1221 | assigned within a linker script. |
| 1222 | @end itemize |
| 1223 | |
| 1224 | There are some other features of the MRI assembler which are not supported by |
| 1225 | @code{@value{AS}}, typically either because they are difficult or because they |
| 1226 | seem of little consequence. Some of these may be supported in future releases. |
| 1227 | |
| 1228 | @itemize @bullet |
| 1229 | |
| 1230 | @item EBCDIC strings |
| 1231 | |
| 1232 | EBCDIC strings are not supported. |
| 1233 | |
| 1234 | @item packed binary coded decimal |
| 1235 | |
| 1236 | Packed binary coded decimal is not supported. This means that the @code{DC.P} |
| 1237 | and @code{DCB.P} pseudo-ops are not supported. |
| 1238 | |
| 1239 | @item @code{FEQU} pseudo-op |
| 1240 | |
| 1241 | The m68k @code{FEQU} pseudo-op is not supported. |
| 1242 | |
| 1243 | @item @code{NOOBJ} pseudo-op |
| 1244 | |
| 1245 | The m68k @code{NOOBJ} pseudo-op is not supported. |
| 1246 | |
| 1247 | @item @code{OPT} branch control options |
| 1248 | |
| 1249 | The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB}, |
| 1250 | @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically |
| 1251 | relaxes all branches, whether forward or backward, to an appropriate size, so |
| 1252 | these options serve no purpose. |
| 1253 | |
| 1254 | @item @code{OPT} list control options |
| 1255 | |
| 1256 | The following m68k @code{OPT} list control options are ignored: @code{C}, |
| 1257 | @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M}, |
| 1258 | @code{MEX}, @code{MC}, @code{MD}, @code{X}. |
| 1259 | |
| 1260 | @item other @code{OPT} options |
| 1261 | |
| 1262 | The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O}, |
| 1263 | @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}. |
| 1264 | |
| 1265 | @item @code{OPT} @code{D} option is default |
| 1266 | |
| 1267 | The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler. |
| 1268 | @code{OPT NOD} may be used to turn it off. |
| 1269 | |
| 1270 | @item @code{XREF} pseudo-op. |
| 1271 | |
| 1272 | The m68k @code{XREF} pseudo-op is ignored. |
| 1273 | |
| 1274 | @item @code{.debug} pseudo-op |
| 1275 | |
| 1276 | The i960 @code{.debug} pseudo-op is not supported. |
| 1277 | |
| 1278 | @item @code{.extended} pseudo-op |
| 1279 | |
| 1280 | The i960 @code{.extended} pseudo-op is not supported. |
| 1281 | |
| 1282 | @item @code{.list} pseudo-op. |
| 1283 | |
| 1284 | The various options of the i960 @code{.list} pseudo-op are not supported. |
| 1285 | |
| 1286 | @item @code{.optimize} pseudo-op |
| 1287 | |
| 1288 | The i960 @code{.optimize} pseudo-op is not supported. |
| 1289 | |
| 1290 | @item @code{.output} pseudo-op |
| 1291 | |
| 1292 | The i960 @code{.output} pseudo-op is not supported. |
| 1293 | |
| 1294 | @item @code{.setreal} pseudo-op |
| 1295 | |
| 1296 | The i960 @code{.setreal} pseudo-op is not supported. |
| 1297 | |
| 1298 | @end itemize |
| 1299 | |
| 1300 | @node MD |
| 1301 | @section Dependency tracking: @code{--MD} |
| 1302 | |
| 1303 | @kindex --MD |
| 1304 | @cindex dependency tracking |
| 1305 | @cindex make rules |
| 1306 | |
| 1307 | @code{@value{AS}} can generate a dependency file for the file it creates. This |
| 1308 | file consists of a single rule suitable for @code{make} describing the |
| 1309 | dependencies of the main source file. |
| 1310 | |
| 1311 | The rule is written to the file named in its argument. |
| 1312 | |
| 1313 | This feature is used in the automatic updating of makefiles. |
| 1314 | |
| 1315 | @node o |
| 1316 | @section Name the Object File: @code{-o} |
| 1317 | |
| 1318 | @kindex -o |
| 1319 | @cindex naming object file |
| 1320 | @cindex object file name |
| 1321 | There is always one object file output when you run @code{@value{AS}}. By |
| 1322 | default it has the name |
| 1323 | @ifset GENERIC |
| 1324 | @ifset I960 |
| 1325 | @file{a.out} (or @file{b.out}, for Intel 960 targets only). |
| 1326 | @end ifset |
| 1327 | @ifclear I960 |
| 1328 | @file{a.out}. |
| 1329 | @end ifclear |
| 1330 | @end ifset |
| 1331 | @ifclear GENERIC |
| 1332 | @ifset I960 |
| 1333 | @file{b.out}. |
| 1334 | @end ifset |
| 1335 | @ifclear I960 |
| 1336 | @file{a.out}. |
| 1337 | @end ifclear |
| 1338 | @end ifclear |
| 1339 | You use this option (which takes exactly one filename) to give the |
| 1340 | object file a different name. |
| 1341 | |
| 1342 | Whatever the object file is called, @code{@value{AS}} overwrites any |
| 1343 | existing file of the same name. |
| 1344 | |
| 1345 | @node R |
| 1346 | @section Join Data and Text Sections: @code{-R} |
| 1347 | |
| 1348 | @kindex -R |
| 1349 | @cindex data and text sections, joining |
| 1350 | @cindex text and data sections, joining |
| 1351 | @cindex joining text and data sections |
| 1352 | @cindex merging text and data sections |
| 1353 | @code{-R} tells @code{@value{AS}} to write the object file as if all |
| 1354 | data-section data lives in the text section. This is only done at |
| 1355 | the very last moment: your binary data are the same, but data |
| 1356 | section parts are relocated differently. The data section part of |
| 1357 | your object file is zero bytes long because all its bytes are |
| 1358 | appended to the text section. (@xref{Sections,,Sections and Relocation}.) |
| 1359 | |
| 1360 | When you specify @code{-R} it would be possible to generate shorter |
| 1361 | address displacements (because we do not have to cross between text and |
| 1362 | data section). We refrain from doing this simply for compatibility with |
| 1363 | older versions of @code{@value{AS}}. In future, @code{-R} may work this way. |
| 1364 | |
| 1365 | @ifset COFF |
| 1366 | When @code{@value{AS}} is configured for COFF output, |
| 1367 | this option is only useful if you use sections named @samp{.text} and |
| 1368 | @samp{.data}. |
| 1369 | @end ifset |
| 1370 | |
| 1371 | @ifset HPPA |
| 1372 | @code{-R} is not supported for any of the HPPA targets. Using |
| 1373 | @code{-R} generates a warning from @code{@value{AS}}. |
| 1374 | @end ifset |
| 1375 | |
| 1376 | @node statistics |
| 1377 | @section Display Assembly Statistics: @code{--statistics} |
| 1378 | |
| 1379 | @kindex --statistics |
| 1380 | @cindex statistics, about assembly |
| 1381 | @cindex time, total for assembly |
| 1382 | @cindex space used, maximum for assembly |
| 1383 | Use @samp{--statistics} to display two statistics about the resources used by |
| 1384 | @code{@value{AS}}: the maximum amount of space allocated during the assembly |
| 1385 | (in bytes), and the total execution time taken for the assembly (in @sc{cpu} |
| 1386 | seconds). |
| 1387 | |
| 1388 | @node traditional-format |
| 1389 | @section Compatible output: @code{--traditional-format} |
| 1390 | |
| 1391 | @kindex --traditional-format |
| 1392 | For some targets, the output of @code{@value{AS}} is different in some ways |
| 1393 | from the output of some existing assembler. This switch requests |
| 1394 | @code{@value{AS}} to use the traditional format instead. |
| 1395 | |
| 1396 | For example, it disables the exception frame optimizations which |
| 1397 | @code{@value{AS}} normally does by default on @code{@value{GCC}} output. |
| 1398 | |
| 1399 | @node v |
| 1400 | @section Announce Version: @code{-v} |
| 1401 | |
| 1402 | @kindex -v |
| 1403 | @kindex -version |
| 1404 | @cindex assembler version |
| 1405 | @cindex version of assembler |
| 1406 | You can find out what version of as is running by including the |
| 1407 | option @samp{-v} (which you can also spell as @samp{-version}) on the |
| 1408 | command line. |
| 1409 | |
| 1410 | @node W |
| 1411 | @section Control Warnings: @code{-W}, @code{--warn}, @code{--no-warn}, @code{--fatal-warnings} |
| 1412 | |
| 1413 | @code{@value{AS}} should never give a warning or error message when |
| 1414 | assembling compiler output. But programs written by people often |
| 1415 | cause @code{@value{AS}} to give a warning that a particular assumption was |
| 1416 | made. All such warnings are directed to the standard error file. |
| 1417 | |
| 1418 | @kindex @samp{-W} |
| 1419 | @kindex @samp{--no-warn} |
| 1420 | @cindex suppressing warnings |
| 1421 | @cindex warnings, suppressing |
| 1422 | If you use the @code{-W} and @code{--no-warn} options, no warnings are issued. |
| 1423 | This only affects the warning messages: it does not change any particular of |
| 1424 | how @code{@value{AS}} assembles your file. Errors, which stop the assembly, |
| 1425 | are still reported. |
| 1426 | |
| 1427 | @kindex @samp{--fatal-warnings} |
| 1428 | @cindex errors, caused by warnings |
| 1429 | @cindex warnings, causing error |
| 1430 | If you use the @code{--fatal-warnings} option, @code{@value{AS}} considers |
| 1431 | files that generate warnings to be in error. |
| 1432 | |
| 1433 | @kindex @samp{--warn} |
| 1434 | @cindex warnings, switching on |
| 1435 | You can switch these options off again by specifying @code{--warn}, which |
| 1436 | causes warnings to be output as usual. |
| 1437 | |
| 1438 | @node Z |
| 1439 | @section Generate Object File in Spite of Errors: @code{-Z} |
| 1440 | @cindex object file, after errors |
| 1441 | @cindex errors, continuing after |
| 1442 | After an error message, @code{@value{AS}} normally produces no output. If for |
| 1443 | some reason you are interested in object file output even after |
| 1444 | @code{@value{AS}} gives an error message on your program, use the @samp{-Z} |
| 1445 | option. If there are any errors, @code{@value{AS}} continues anyways, and |
| 1446 | writes an object file after a final warning message of the form @samp{@var{n} |
| 1447 | errors, @var{m} warnings, generating bad object file.} |
| 1448 | |
| 1449 | @node Syntax |
| 1450 | @chapter Syntax |
| 1451 | |
| 1452 | @cindex machine-independent syntax |
| 1453 | @cindex syntax, machine-independent |
| 1454 | This chapter describes the machine-independent syntax allowed in a |
| 1455 | source file. @code{@value{AS}} syntax is similar to what many other |
| 1456 | assemblers use; it is inspired by the BSD 4.2 |
| 1457 | @ifclear VAX |
| 1458 | assembler. |
| 1459 | @end ifclear |
| 1460 | @ifset VAX |
| 1461 | assembler, except that @code{@value{AS}} does not assemble Vax bit-fields. |
| 1462 | @end ifset |
| 1463 | |
| 1464 | @menu |
| 1465 | * Preprocessing:: Preprocessing |
| 1466 | * Whitespace:: Whitespace |
| 1467 | * Comments:: Comments |
| 1468 | * Symbol Intro:: Symbols |
| 1469 | * Statements:: Statements |
| 1470 | * Constants:: Constants |
| 1471 | @end menu |
| 1472 | |
| 1473 | @node Preprocessing |
| 1474 | @section Preprocessing |
| 1475 | |
| 1476 | @cindex preprocessing |
| 1477 | The @code{@value{AS}} internal preprocessor: |
| 1478 | @itemize @bullet |
| 1479 | @cindex whitespace, removed by preprocessor |
| 1480 | @item |
| 1481 | adjusts and removes extra whitespace. It leaves one space or tab before |
| 1482 | the keywords on a line, and turns any other whitespace on the line into |
| 1483 | a single space. |
| 1484 | |
| 1485 | @cindex comments, removed by preprocessor |
| 1486 | @item |
| 1487 | removes all comments, replacing them with a single space, or an |
| 1488 | appropriate number of newlines. |
| 1489 | |
| 1490 | @cindex constants, converted by preprocessor |
| 1491 | @item |
| 1492 | converts character constants into the appropriate numeric values. |
| 1493 | @end itemize |
| 1494 | |
| 1495 | It does not do macro processing, include file handling, or |
| 1496 | anything else you may get from your C compiler's preprocessor. You can |
| 1497 | do include file processing with the @code{.include} directive |
| 1498 | (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver |
| 1499 | to get other ``CPP'' style preprocessing, by giving the input file a |
| 1500 | @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of |
| 1501 | Output, gcc.info, Using GNU CC}. |
| 1502 | |
| 1503 | Excess whitespace, comments, and character constants |
| 1504 | cannot be used in the portions of the input text that are not |
| 1505 | preprocessed. |
| 1506 | |
| 1507 | @cindex turning preprocessing on and off |
| 1508 | @cindex preprocessing, turning on and off |
| 1509 | @kindex #NO_APP |
| 1510 | @kindex #APP |
| 1511 | If the first line of an input file is @code{#NO_APP} or if you use the |
| 1512 | @samp{-f} option, whitespace and comments are not removed from the input file. |
| 1513 | Within an input file, you can ask for whitespace and comment removal in |
| 1514 | specific portions of the by putting a line that says @code{#APP} before the |
| 1515 | text that may contain whitespace or comments, and putting a line that says |
| 1516 | @code{#NO_APP} after this text. This feature is mainly intend to support |
| 1517 | @code{asm} statements in compilers whose output is otherwise free of comments |
| 1518 | and whitespace. |
| 1519 | |
| 1520 | @node Whitespace |
| 1521 | @section Whitespace |
| 1522 | |
| 1523 | @cindex whitespace |
| 1524 | @dfn{Whitespace} is one or more blanks or tabs, in any order. |
| 1525 | Whitespace is used to separate symbols, and to make programs neater for |
| 1526 | people to read. Unless within character constants |
| 1527 | (@pxref{Characters,,Character Constants}), any whitespace means the same |
| 1528 | as exactly one space. |
| 1529 | |
| 1530 | @node Comments |
| 1531 | @section Comments |
| 1532 | |
| 1533 | @cindex comments |
| 1534 | There are two ways of rendering comments to @code{@value{AS}}. In both |
| 1535 | cases the comment is equivalent to one space. |
| 1536 | |
| 1537 | Anything from @samp{/*} through the next @samp{*/} is a comment. |
| 1538 | This means you may not nest these comments. |
| 1539 | |
| 1540 | @smallexample |
| 1541 | /* |
| 1542 | The only way to include a newline ('\n') in a comment |
| 1543 | is to use this sort of comment. |
| 1544 | */ |
| 1545 | |
| 1546 | /* This sort of comment does not nest. */ |
| 1547 | @end smallexample |
| 1548 | |
| 1549 | @cindex line comment character |
| 1550 | Anything from the @dfn{line comment} character to the next newline |
| 1551 | is considered a comment and is ignored. The line comment character is |
| 1552 | @ifset A29K |
| 1553 | @samp{;} for the AMD 29K family; |
| 1554 | @end ifset |
| 1555 | @ifset ARC |
| 1556 | @samp{;} on the ARC; |
| 1557 | @end ifset |
| 1558 | @ifset H8/300 |
| 1559 | @samp{;} for the H8/300 family; |
| 1560 | @end ifset |
| 1561 | @ifset H8/500 |
| 1562 | @samp{!} for the H8/500 family; |
| 1563 | @end ifset |
| 1564 | @ifset HPPA |
| 1565 | @samp{;} for the HPPA; |
| 1566 | @end ifset |
| 1567 | @ifset I960 |
| 1568 | @samp{#} on the i960; |
| 1569 | @end ifset |
| 1570 | @ifset PJ |
| 1571 | @samp{;} for picoJava; |
| 1572 | @end ifset |
| 1573 | @ifset SH |
| 1574 | @samp{!} for the Hitachi SH; |
| 1575 | @end ifset |
| 1576 | @ifset SPARC |
| 1577 | @samp{!} on the SPARC; |
| 1578 | @end ifset |
| 1579 | @ifset M32R |
| 1580 | @samp{#} on the m32r; |
| 1581 | @end ifset |
| 1582 | @ifset M680X0 |
| 1583 | @samp{|} on the 680x0; |
| 1584 | @end ifset |
| 1585 | @ifset VAX |
| 1586 | @samp{#} on the Vax; |
| 1587 | @end ifset |
| 1588 | @ifset Z8000 |
| 1589 | @samp{!} for the Z8000; |
| 1590 | @end ifset |
| 1591 | @ifset V850 |
| 1592 | @samp{#} on the V850; |
| 1593 | @end ifset |
| 1594 | see @ref{Machine Dependencies}. @refill |
| 1595 | @c FIXME What about i386, m88k, i860? |
| 1596 | |
| 1597 | @ifset GENERIC |
| 1598 | On some machines there are two different line comment characters. One |
| 1599 | character only begins a comment if it is the first non-whitespace character on |
| 1600 | a line, while the other always begins a comment. |
| 1601 | @end ifset |
| 1602 | |
| 1603 | @ifset V850 |
| 1604 | The V850 assembler also supports a double dash as starting a comment that |
| 1605 | extends to the end of the line. |
| 1606 | |
| 1607 | @samp{--}; |
| 1608 | @end ifset |
| 1609 | |
| 1610 | @kindex # |
| 1611 | @cindex lines starting with @code{#} |
| 1612 | @cindex logical line numbers |
| 1613 | To be compatible with past assemblers, lines that begin with @samp{#} have a |
| 1614 | special interpretation. Following the @samp{#} should be an absolute |
| 1615 | expression (@pxref{Expressions}): the logical line number of the @emph{next} |
| 1616 | line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a |
| 1617 | new logical file name. The rest of the line, if any, should be whitespace. |
| 1618 | |
| 1619 | If the first non-whitespace characters on the line are not numeric, |
| 1620 | the line is ignored. (Just like a comment.) |
| 1621 | |
| 1622 | @smallexample |
| 1623 | # This is an ordinary comment. |
| 1624 | # 42-6 "new_file_name" # New logical file name |
| 1625 | # This is logical line # 36. |
| 1626 | @end smallexample |
| 1627 | This feature is deprecated, and may disappear from future versions |
| 1628 | of @code{@value{AS}}. |
| 1629 | |
| 1630 | @node Symbol Intro |
| 1631 | @section Symbols |
| 1632 | |
| 1633 | @cindex characters used in symbols |
| 1634 | @ifclear SPECIAL-SYMS |
| 1635 | A @dfn{symbol} is one or more characters chosen from the set of all |
| 1636 | letters (both upper and lower case), digits and the three characters |
| 1637 | @samp{_.$}. |
| 1638 | @end ifclear |
| 1639 | @ifset SPECIAL-SYMS |
| 1640 | @ifclear GENERIC |
| 1641 | @ifset H8 |
| 1642 | A @dfn{symbol} is one or more characters chosen from the set of all |
| 1643 | letters (both upper and lower case), digits and the three characters |
| 1644 | @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in |
| 1645 | symbol names.) |
| 1646 | @end ifset |
| 1647 | @end ifclear |
| 1648 | @end ifset |
| 1649 | @ifset GENERIC |
| 1650 | On most machines, you can also use @code{$} in symbol names; exceptions |
| 1651 | are noted in @ref{Machine Dependencies}. |
| 1652 | @end ifset |
| 1653 | No symbol may begin with a digit. Case is significant. |
| 1654 | There is no length limit: all characters are significant. Symbols are |
| 1655 | delimited by characters not in that set, or by the beginning of a file |
| 1656 | (since the source program must end with a newline, the end of a file is |
| 1657 | not a possible symbol delimiter). @xref{Symbols}. |
| 1658 | @cindex length of symbols |
| 1659 | |
| 1660 | @node Statements |
| 1661 | @section Statements |
| 1662 | |
| 1663 | @cindex statements, structure of |
| 1664 | @cindex line separator character |
| 1665 | @cindex statement separator character |
| 1666 | @ifclear GENERIC |
| 1667 | @ifclear abnormal-separator |
| 1668 | A @dfn{statement} ends at a newline character (@samp{\n}) or at a |
| 1669 | semicolon (@samp{;}). The newline or semicolon is considered part of |
| 1670 | the preceding statement. Newlines and semicolons within character |
| 1671 | constants are an exception: they do not end statements. |
| 1672 | @end ifclear |
| 1673 | @ifset abnormal-separator |
| 1674 | @ifset A29K |
| 1675 | A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at'' |
| 1676 | sign (@samp{@@}). The newline or at sign is considered part of the |
| 1677 | preceding statement. Newlines and at signs within character constants |
| 1678 | are an exception: they do not end statements. |
| 1679 | @end ifset |
| 1680 | @ifset HPPA |
| 1681 | A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation |
| 1682 | point (@samp{!}). The newline or exclamation point is considered part of the |
| 1683 | preceding statement. Newlines and exclamation points within character |
| 1684 | constants are an exception: they do not end statements. |
| 1685 | @end ifset |
| 1686 | @ifset H8 |
| 1687 | A @dfn{statement} ends at a newline character (@samp{\n}); or (for the |
| 1688 | H8/300) a dollar sign (@samp{$}); or (for the |
| 1689 | Hitachi-SH or the |
| 1690 | H8/500) a semicolon |
| 1691 | (@samp{;}). The newline or separator character is considered part of |
| 1692 | the preceding statement. Newlines and separators within character |
| 1693 | constants are an exception: they do not end statements. |
| 1694 | @end ifset |
| 1695 | @end ifset |
| 1696 | @end ifclear |
| 1697 | @ifset GENERIC |
| 1698 | A @dfn{statement} ends at a newline character (@samp{\n}) or line |
| 1699 | separator character. (The line separator is usually @samp{;}, unless |
| 1700 | this conflicts with the comment character; @pxref{Machine Dependencies}.) The |
| 1701 | newline or separator character is considered part of the preceding |
| 1702 | statement. Newlines and separators within character constants are an |
| 1703 | exception: they do not end statements. |
| 1704 | @end ifset |
| 1705 | |
| 1706 | @cindex newline, required at file end |
| 1707 | @cindex EOF, newline must precede |
| 1708 | It is an error to end any statement with end-of-file: the last |
| 1709 | character of any input file should be a newline.@refill |
| 1710 | |
| 1711 | An empty statement is allowed, and may include whitespace. It is ignored. |
| 1712 | |
| 1713 | @cindex instructions and directives |
| 1714 | @cindex directives and instructions |
| 1715 | @c "key symbol" is not used elsewhere in the document; seems pedantic to |
| 1716 | @c @defn{} it in that case, as was done previously... doc@cygnus.com, |
| 1717 | @c 13feb91. |
| 1718 | A statement begins with zero or more labels, optionally followed by a |
| 1719 | key symbol which determines what kind of statement it is. The key |
| 1720 | symbol determines the syntax of the rest of the statement. If the |
| 1721 | symbol begins with a dot @samp{.} then the statement is an assembler |
| 1722 | directive: typically valid for any computer. If the symbol begins with |
| 1723 | a letter the statement is an assembly language @dfn{instruction}: it |
| 1724 | assembles into a machine language instruction. |
| 1725 | @ifset GENERIC |
| 1726 | Different versions of @code{@value{AS}} for different computers |
| 1727 | recognize different instructions. In fact, the same symbol may |
| 1728 | represent a different instruction in a different computer's assembly |
| 1729 | language.@refill |
| 1730 | @end ifset |
| 1731 | |
| 1732 | @cindex @code{:} (label) |
| 1733 | @cindex label (@code{:}) |
| 1734 | A label is a symbol immediately followed by a colon (@code{:}). |
| 1735 | Whitespace before a label or after a colon is permitted, but you may not |
| 1736 | have whitespace between a label's symbol and its colon. @xref{Labels}. |
| 1737 | |
| 1738 | @ifset HPPA |
| 1739 | For HPPA targets, labels need not be immediately followed by a colon, but |
| 1740 | the definition of a label must begin in column zero. This also implies that |
| 1741 | only one label may be defined on each line. |
| 1742 | @end ifset |
| 1743 | |
| 1744 | @smallexample |
| 1745 | label: .directive followed by something |
| 1746 | another_label: # This is an empty statement. |
| 1747 | instruction operand_1, operand_2, @dots{} |
| 1748 | @end smallexample |
| 1749 | |
| 1750 | @node Constants |
| 1751 | @section Constants |
| 1752 | |
| 1753 | @cindex constants |
| 1754 | A constant is a number, written so that its value is known by |
| 1755 | inspection, without knowing any context. Like this: |
| 1756 | @smallexample |
| 1757 | @group |
| 1758 | .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value. |
| 1759 | .ascii "Ring the bell\7" # A string constant. |
| 1760 | .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum. |
| 1761 | .float 0f-314159265358979323846264338327\ |
| 1762 | 95028841971.693993751E-40 # - pi, a flonum. |
| 1763 | @end group |
| 1764 | @end smallexample |
| 1765 | |
| 1766 | @menu |
| 1767 | * Characters:: Character Constants |
| 1768 | * Numbers:: Number Constants |
| 1769 | @end menu |
| 1770 | |
| 1771 | @node Characters |
| 1772 | @subsection Character Constants |
| 1773 | |
| 1774 | @cindex character constants |
| 1775 | @cindex constants, character |
| 1776 | There are two kinds of character constants. A @dfn{character} stands |
| 1777 | for one character in one byte and its value may be used in |
| 1778 | numeric expressions. String constants (properly called string |
| 1779 | @emph{literals}) are potentially many bytes and their values may not be |
| 1780 | used in arithmetic expressions. |
| 1781 | |
| 1782 | @menu |
| 1783 | * Strings:: Strings |
| 1784 | * Chars:: Characters |
| 1785 | @end menu |
| 1786 | |
| 1787 | @node Strings |
| 1788 | @subsubsection Strings |
| 1789 | |
| 1790 | @cindex string constants |
| 1791 | @cindex constants, string |
| 1792 | A @dfn{string} is written between double-quotes. It may contain |
| 1793 | double-quotes or null characters. The way to get special characters |
| 1794 | into a string is to @dfn{escape} these characters: precede them with |
| 1795 | a backslash @samp{\} character. For example @samp{\\} represents |
| 1796 | one backslash: the first @code{\} is an escape which tells |
| 1797 | @code{@value{AS}} to interpret the second character literally as a backslash |
| 1798 | (which prevents @code{@value{AS}} from recognizing the second @code{\} as an |
| 1799 | escape character). The complete list of escapes follows. |
| 1800 | |
| 1801 | @cindex escape codes, character |
| 1802 | @cindex character escape codes |
| 1803 | @table @kbd |
| 1804 | @c @item \a |
| 1805 | @c Mnemonic for ACKnowledge; for ASCII this is octal code 007. |
| 1806 | @c |
| 1807 | @cindex @code{\b} (backspace character) |
| 1808 | @cindex backspace (@code{\b}) |
| 1809 | @item \b |
| 1810 | Mnemonic for backspace; for ASCII this is octal code 010. |
| 1811 | |
| 1812 | @c @item \e |
| 1813 | @c Mnemonic for EOText; for ASCII this is octal code 004. |
| 1814 | @c |
| 1815 | @cindex @code{\f} (formfeed character) |
| 1816 | @cindex formfeed (@code{\f}) |
| 1817 | @item \f |
| 1818 | Mnemonic for FormFeed; for ASCII this is octal code 014. |
| 1819 | |
| 1820 | @cindex @code{\n} (newline character) |
| 1821 | @cindex newline (@code{\n}) |
| 1822 | @item \n |
| 1823 | Mnemonic for newline; for ASCII this is octal code 012. |
| 1824 | |
| 1825 | @c @item \p |
| 1826 | @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}. |
| 1827 | @c |
| 1828 | @cindex @code{\r} (carriage return character) |
| 1829 | @cindex carriage return (@code{\r}) |
| 1830 | @item \r |
| 1831 | Mnemonic for carriage-Return; for ASCII this is octal code 015. |
| 1832 | |
| 1833 | @c @item \s |
| 1834 | @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with |
| 1835 | @c other assemblers. |
| 1836 | @c |
| 1837 | @cindex @code{\t} (tab) |
| 1838 | @cindex tab (@code{\t}) |
| 1839 | @item \t |
| 1840 | Mnemonic for horizontal Tab; for ASCII this is octal code 011. |
| 1841 | |
| 1842 | @c @item \v |
| 1843 | @c Mnemonic for Vertical tab; for ASCII this is octal code 013. |
| 1844 | @c @item \x @var{digit} @var{digit} @var{digit} |
| 1845 | @c A hexadecimal character code. The numeric code is 3 hexadecimal digits. |
| 1846 | @c |
| 1847 | @cindex @code{\@var{ddd}} (octal character code) |
| 1848 | @cindex octal character code (@code{\@var{ddd}}) |
| 1849 | @item \ @var{digit} @var{digit} @var{digit} |
| 1850 | An octal character code. The numeric code is 3 octal digits. |
| 1851 | For compatibility with other Unix systems, 8 and 9 are accepted as digits: |
| 1852 | for example, @code{\008} has the value 010, and @code{\009} the value 011. |
| 1853 | |
| 1854 | @cindex @code{\@var{xd...}} (hex character code) |
| 1855 | @cindex hex character code (@code{\@var{xd...}}) |
| 1856 | @item \@code{x} @var{hex-digits...} |
| 1857 | A hex character code. All trailing hex digits are combined. Either upper or |
| 1858 | lower case @code{x} works. |
| 1859 | |
| 1860 | @cindex @code{\\} (@samp{\} character) |
| 1861 | @cindex backslash (@code{\\}) |
| 1862 | @item \\ |
| 1863 | Represents one @samp{\} character. |
| 1864 | |
| 1865 | @c @item \' |
| 1866 | @c Represents one @samp{'} (accent acute) character. |
| 1867 | @c This is needed in single character literals |
| 1868 | @c (@xref{Characters,,Character Constants}.) to represent |
| 1869 | @c a @samp{'}. |
| 1870 | @c |
| 1871 | @cindex @code{\"} (doublequote character) |
| 1872 | @cindex doublequote (@code{\"}) |
| 1873 | @item \" |
| 1874 | Represents one @samp{"} character. Needed in strings to represent |
| 1875 | this character, because an unescaped @samp{"} would end the string. |
| 1876 | |
| 1877 | @item \ @var{anything-else} |
| 1878 | Any other character when escaped by @kbd{\} gives a warning, but |
| 1879 | assembles as if the @samp{\} was not present. The idea is that if |
| 1880 | you used an escape sequence you clearly didn't want the literal |
| 1881 | interpretation of the following character. However @code{@value{AS}} has no |
| 1882 | other interpretation, so @code{@value{AS}} knows it is giving you the wrong |
| 1883 | code and warns you of the fact. |
| 1884 | @end table |
| 1885 | |
| 1886 | Which characters are escapable, and what those escapes represent, |
| 1887 | varies widely among assemblers. The current set is what we think |
| 1888 | the BSD 4.2 assembler recognizes, and is a subset of what most C |
| 1889 | compilers recognize. If you are in doubt, do not use an escape |
| 1890 | sequence. |
| 1891 | |
| 1892 | @node Chars |
| 1893 | @subsubsection Characters |
| 1894 | |
| 1895 | @cindex single character constant |
| 1896 | @cindex character, single |
| 1897 | @cindex constant, single character |
| 1898 | A single character may be written as a single quote immediately |
| 1899 | followed by that character. The same escapes apply to characters as |
| 1900 | to strings. So if you want to write the character backslash, you |
| 1901 | must write @kbd{'\\} where the first @code{\} escapes the second |
| 1902 | @code{\}. As you can see, the quote is an acute accent, not a |
| 1903 | grave accent. A newline |
| 1904 | @ifclear GENERIC |
| 1905 | @ifclear abnormal-separator |
| 1906 | (or semicolon @samp{;}) |
| 1907 | @end ifclear |
| 1908 | @ifset abnormal-separator |
| 1909 | @ifset A29K |
| 1910 | (or at sign @samp{@@}) |
| 1911 | @end ifset |
| 1912 | @ifset H8 |
| 1913 | (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the |
| 1914 | Hitachi SH or |
| 1915 | H8/500) |
| 1916 | @end ifset |
| 1917 | @end ifset |
| 1918 | @end ifclear |
| 1919 | immediately following an acute accent is taken as a literal character |
| 1920 | and does not count as the end of a statement. The value of a character |
| 1921 | constant in a numeric expression is the machine's byte-wide code for |
| 1922 | that character. @code{@value{AS}} assumes your character code is ASCII: |
| 1923 | @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill |
| 1924 | |
| 1925 | @node Numbers |
| 1926 | @subsection Number Constants |
| 1927 | |
| 1928 | @cindex constants, number |
| 1929 | @cindex number constants |
| 1930 | @code{@value{AS}} distinguishes three kinds of numbers according to how they |
| 1931 | are stored in the target machine. @emph{Integers} are numbers that |
| 1932 | would fit into an @code{int} in the C language. @emph{Bignums} are |
| 1933 | integers, but they are stored in more than 32 bits. @emph{Flonums} |
| 1934 | are floating point numbers, described below. |
| 1935 | |
| 1936 | @menu |
| 1937 | * Integers:: Integers |
| 1938 | * Bignums:: Bignums |
| 1939 | * Flonums:: Flonums |
| 1940 | @ifclear GENERIC |
| 1941 | @ifset I960 |
| 1942 | * Bit Fields:: Bit Fields |
| 1943 | @end ifset |
| 1944 | @end ifclear |
| 1945 | @end menu |
| 1946 | |
| 1947 | @node Integers |
| 1948 | @subsubsection Integers |
| 1949 | @cindex integers |
| 1950 | @cindex constants, integer |
| 1951 | |
| 1952 | @cindex binary integers |
| 1953 | @cindex integers, binary |
| 1954 | A binary integer is @samp{0b} or @samp{0B} followed by zero or more of |
| 1955 | the binary digits @samp{01}. |
| 1956 | |
| 1957 | @cindex octal integers |
| 1958 | @cindex integers, octal |
| 1959 | An octal integer is @samp{0} followed by zero or more of the octal |
| 1960 | digits (@samp{01234567}). |
| 1961 | |
| 1962 | @cindex decimal integers |
| 1963 | @cindex integers, decimal |
| 1964 | A decimal integer starts with a non-zero digit followed by zero or |
| 1965 | more digits (@samp{0123456789}). |
| 1966 | |
| 1967 | @cindex hexadecimal integers |
| 1968 | @cindex integers, hexadecimal |
| 1969 | A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or |
| 1970 | more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}. |
| 1971 | |
| 1972 | Integers have the usual values. To denote a negative integer, use |
| 1973 | the prefix operator @samp{-} discussed under expressions |
| 1974 | (@pxref{Prefix Ops,,Prefix Operators}). |
| 1975 | |
| 1976 | @node Bignums |
| 1977 | @subsubsection Bignums |
| 1978 | |
| 1979 | @cindex bignums |
| 1980 | @cindex constants, bignum |
| 1981 | A @dfn{bignum} has the same syntax and semantics as an integer |
| 1982 | except that the number (or its negative) takes more than 32 bits to |
| 1983 | represent in binary. The distinction is made because in some places |
| 1984 | integers are permitted while bignums are not. |
| 1985 | |
| 1986 | @node Flonums |
| 1987 | @subsubsection Flonums |
| 1988 | @cindex flonums |
| 1989 | @cindex floating point numbers |
| 1990 | @cindex constants, floating point |
| 1991 | |
| 1992 | @cindex precision, floating point |
| 1993 | A @dfn{flonum} represents a floating point number. The translation is |
| 1994 | indirect: a decimal floating point number from the text is converted by |
| 1995 | @code{@value{AS}} to a generic binary floating point number of more than |
| 1996 | sufficient precision. This generic floating point number is converted |
| 1997 | to a particular computer's floating point format (or formats) by a |
| 1998 | portion of @code{@value{AS}} specialized to that computer. |
| 1999 | |
| 2000 | A flonum is written by writing (in order) |
| 2001 | @itemize @bullet |
| 2002 | @item |
| 2003 | The digit @samp{0}. |
| 2004 | @ifset HPPA |
| 2005 | (@samp{0} is optional on the HPPA.) |
| 2006 | @end ifset |
| 2007 | |
| 2008 | @item |
| 2009 | A letter, to tell @code{@value{AS}} the rest of the number is a flonum. |
| 2010 | @ifset GENERIC |
| 2011 | @kbd{e} is recommended. Case is not important. |
| 2012 | @ignore |
| 2013 | @c FIXME: verify if flonum syntax really this vague for most cases |
| 2014 | (Any otherwise illegal letter works here, but that might be changed. Vax BSD |
| 2015 | 4.2 assembler seems to allow any of @samp{defghDEFGH}.) |
| 2016 | @end ignore |
| 2017 | |
| 2018 | On the H8/300, H8/500, |
| 2019 | Hitachi SH, |
| 2020 | and AMD 29K architectures, the letter must be |
| 2021 | one of the letters @samp{DFPRSX} (in upper or lower case). |
| 2022 | |
| 2023 | On the ARC, the letter must be one of the letters @samp{DFRS} |
| 2024 | (in upper or lower case). |
| 2025 | |
| 2026 | On the Intel 960 architecture, the letter must be |
| 2027 | one of the letters @samp{DFT} (in upper or lower case). |
| 2028 | |
| 2029 | On the HPPA architecture, the letter must be @samp{E} (upper case only). |
| 2030 | @end ifset |
| 2031 | @ifclear GENERIC |
| 2032 | @ifset A29K |
| 2033 | One of the letters @samp{DFPRSX} (in upper or lower case). |
| 2034 | @end ifset |
| 2035 | @ifset ARC |
| 2036 | One of the letters @samp{DFRS} (in upper or lower case). |
| 2037 | @end ifset |
| 2038 | @ifset H8 |
| 2039 | One of the letters @samp{DFPRSX} (in upper or lower case). |
| 2040 | @end ifset |
| 2041 | @ifset HPPA |
| 2042 | The letter @samp{E} (upper case only). |
| 2043 | @end ifset |
| 2044 | @ifset I960 |
| 2045 | One of the letters @samp{DFT} (in upper or lower case). |
| 2046 | @end ifset |
| 2047 | @end ifclear |
| 2048 | |
| 2049 | @item |
| 2050 | An optional sign: either @samp{+} or @samp{-}. |
| 2051 | |
| 2052 | @item |
| 2053 | An optional @dfn{integer part}: zero or more decimal digits. |
| 2054 | |
| 2055 | @item |
| 2056 | An optional @dfn{fractional part}: @samp{.} followed by zero |
| 2057 | or more decimal digits. |
| 2058 | |
| 2059 | @item |
| 2060 | An optional exponent, consisting of: |
| 2061 | |
| 2062 | @itemize @bullet |
| 2063 | @item |
| 2064 | An @samp{E} or @samp{e}. |
| 2065 | @c I can't find a config where "EXP_CHARS" is other than 'eE', but in |
| 2066 | @c principle this can perfectly well be different on different targets. |
| 2067 | @item |
| 2068 | Optional sign: either @samp{+} or @samp{-}. |
| 2069 | @item |
| 2070 | One or more decimal digits. |
| 2071 | @end itemize |
| 2072 | |
| 2073 | @end itemize |
| 2074 | |
| 2075 | At least one of the integer part or the fractional part must be |
| 2076 | present. The floating point number has the usual base-10 value. |
| 2077 | |
| 2078 | @code{@value{AS}} does all processing using integers. Flonums are computed |
| 2079 | independently of any floating point hardware in the computer running |
| 2080 | @code{@value{AS}}. |
| 2081 | |
| 2082 | @ifclear GENERIC |
| 2083 | @ifset I960 |
| 2084 | @c Bit fields are written as a general facility but are also controlled |
| 2085 | @c by a conditional-compilation flag---which is as of now (21mar91) |
| 2086 | @c turned on only by the i960 config of GAS. |
| 2087 | @node Bit Fields |
| 2088 | @subsubsection Bit Fields |
| 2089 | |
| 2090 | @cindex bit fields |
| 2091 | @cindex constants, bit field |
| 2092 | You can also define numeric constants as @dfn{bit fields}. |
| 2093 | specify two numbers separated by a colon--- |
| 2094 | @example |
| 2095 | @var{mask}:@var{value} |
| 2096 | @end example |
| 2097 | @noindent |
| 2098 | @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and |
| 2099 | @var{value}. |
| 2100 | |
| 2101 | The resulting number is then packed |
| 2102 | @ifset GENERIC |
| 2103 | @c this conditional paren in case bit fields turned on elsewhere than 960 |
| 2104 | (in host-dependent byte order) |
| 2105 | @end ifset |
| 2106 | into a field whose width depends on which assembler directive has the |
| 2107 | bit-field as its argument. Overflow (a result from the bitwise and |
| 2108 | requiring more binary digits to represent) is not an error; instead, |
| 2109 | more constants are generated, of the specified width, beginning with the |
| 2110 | least significant digits.@refill |
| 2111 | |
| 2112 | The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long}, |
| 2113 | @code{.short}, and @code{.word} accept bit-field arguments. |
| 2114 | @end ifset |
| 2115 | @end ifclear |
| 2116 | |
| 2117 | @node Sections |
| 2118 | @chapter Sections and Relocation |
| 2119 | @cindex sections |
| 2120 | @cindex relocation |
| 2121 | |
| 2122 | @menu |
| 2123 | * Secs Background:: Background |
| 2124 | * Ld Sections:: Linker Sections |
| 2125 | * As Sections:: Assembler Internal Sections |
| 2126 | * Sub-Sections:: Sub-Sections |
| 2127 | * bss:: bss Section |
| 2128 | @end menu |
| 2129 | |
| 2130 | @node Secs Background |
| 2131 | @section Background |
| 2132 | |
| 2133 | Roughly, a section is a range of addresses, with no gaps; all data |
| 2134 | ``in'' those addresses is treated the same for some particular purpose. |
| 2135 | For example there may be a ``read only'' section. |
| 2136 | |
| 2137 | @cindex linker, and assembler |
| 2138 | @cindex assembler, and linker |
| 2139 | The linker @code{@value{LD}} reads many object files (partial programs) and |
| 2140 | combines their contents to form a runnable program. When @code{@value{AS}} |
| 2141 | emits an object file, the partial program is assumed to start at address 0. |
| 2142 | @code{@value{LD}} assigns the final addresses for the partial program, so that |
| 2143 | different partial programs do not overlap. This is actually an |
| 2144 | oversimplification, but it suffices to explain how @code{@value{AS}} uses |
| 2145 | sections. |
| 2146 | |
| 2147 | @code{@value{LD}} moves blocks of bytes of your program to their run-time |
| 2148 | addresses. These blocks slide to their run-time addresses as rigid |
| 2149 | units; their length does not change and neither does the order of bytes |
| 2150 | within them. Such a rigid unit is called a @emph{section}. Assigning |
| 2151 | run-time addresses to sections is called @dfn{relocation}. It includes |
| 2152 | the task of adjusting mentions of object-file addresses so they refer to |
| 2153 | the proper run-time addresses. |
| 2154 | @ifset H8 |
| 2155 | For the H8/300 and H8/500, |
| 2156 | and for the Hitachi SH, |
| 2157 | @code{@value{AS}} pads sections if needed to |
| 2158 | ensure they end on a word (sixteen bit) boundary. |
| 2159 | @end ifset |
| 2160 | |
| 2161 | @cindex standard assembler sections |
| 2162 | An object file written by @code{@value{AS}} has at least three sections, any |
| 2163 | of which may be empty. These are named @dfn{text}, @dfn{data} and |
| 2164 | @dfn{bss} sections. |
| 2165 | |
| 2166 | @ifset COFF |
| 2167 | @ifset GENERIC |
| 2168 | When it generates COFF output, |
| 2169 | @end ifset |
| 2170 | @code{@value{AS}} can also generate whatever other named sections you specify |
| 2171 | using the @samp{.section} directive (@pxref{Section,,@code{.section}}). |
| 2172 | If you do not use any directives that place output in the @samp{.text} |
| 2173 | or @samp{.data} sections, these sections still exist, but are empty. |
| 2174 | @end ifset |
| 2175 | |
| 2176 | @ifset HPPA |
| 2177 | @ifset GENERIC |
| 2178 | When @code{@value{AS}} generates SOM or ELF output for the HPPA, |
| 2179 | @end ifset |
| 2180 | @code{@value{AS}} can also generate whatever other named sections you |
| 2181 | specify using the @samp{.space} and @samp{.subspace} directives. See |
| 2182 | @cite{HP9000 Series 800 Assembly Language Reference Manual} |
| 2183 | (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace} |
| 2184 | assembler directives. |
| 2185 | |
| 2186 | @ifset SOM |
| 2187 | Additionally, @code{@value{AS}} uses different names for the standard |
| 2188 | text, data, and bss sections when generating SOM output. Program text |
| 2189 | is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and |
| 2190 | BSS into @samp{$BSS$}. |
| 2191 | @end ifset |
| 2192 | @end ifset |
| 2193 | |
| 2194 | Within the object file, the text section starts at address @code{0}, the |
| 2195 | data section follows, and the bss section follows the data section. |
| 2196 | |
| 2197 | @ifset HPPA |
| 2198 | When generating either SOM or ELF output files on the HPPA, the text |
| 2199 | section starts at address @code{0}, the data section at address |
| 2200 | @code{0x4000000}, and the bss section follows the data section. |
| 2201 | @end ifset |
| 2202 | |
| 2203 | To let @code{@value{LD}} know which data changes when the sections are |
| 2204 | relocated, and how to change that data, @code{@value{AS}} also writes to the |
| 2205 | object file details of the relocation needed. To perform relocation |
| 2206 | @code{@value{LD}} must know, each time an address in the object |
| 2207 | file is mentioned: |
| 2208 | @itemize @bullet |
| 2209 | @item |
| 2210 | Where in the object file is the beginning of this reference to |
| 2211 | an address? |
| 2212 | @item |
| 2213 | How long (in bytes) is this reference? |
| 2214 | @item |
| 2215 | Which section does the address refer to? What is the numeric value of |
| 2216 | @display |
| 2217 | (@var{address}) @minus{} (@var{start-address of section})? |
| 2218 | @end display |
| 2219 | @item |
| 2220 | Is the reference to an address ``Program-Counter relative''? |
| 2221 | @end itemize |
| 2222 | |
| 2223 | @cindex addresses, format of |
| 2224 | @cindex section-relative addressing |
| 2225 | In fact, every address @code{@value{AS}} ever uses is expressed as |
| 2226 | @display |
| 2227 | (@var{section}) + (@var{offset into section}) |
| 2228 | @end display |
| 2229 | @noindent |
| 2230 | Further, most expressions @code{@value{AS}} computes have this section-relative |
| 2231 | nature. |
| 2232 | @ifset SOM |
| 2233 | (For some object formats, such as SOM for the HPPA, some expressions are |
| 2234 | symbol-relative instead.) |
| 2235 | @end ifset |
| 2236 | |
| 2237 | In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset |
| 2238 | @var{N} into section @var{secname}.'' |
| 2239 | |
| 2240 | Apart from text, data and bss sections you need to know about the |
| 2241 | @dfn{absolute} section. When @code{@value{LD}} mixes partial programs, |
| 2242 | addresses in the absolute section remain unchanged. For example, address |
| 2243 | @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by |
| 2244 | @code{@value{LD}}. Although the linker never arranges two partial programs' |
| 2245 | data sections with overlapping addresses after linking, @emph{by definition} |
| 2246 | their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one |
| 2247 | part of a program is always the same address when the program is running as |
| 2248 | address @code{@{absolute@ 239@}} in any other part of the program. |
| 2249 | |
| 2250 | The idea of sections is extended to the @dfn{undefined} section. Any |
| 2251 | address whose section is unknown at assembly time is by definition |
| 2252 | rendered @{undefined @var{U}@}---where @var{U} is filled in later. |
| 2253 | Since numbers are always defined, the only way to generate an undefined |
| 2254 | address is to mention an undefined symbol. A reference to a named |
| 2255 | common block would be such a symbol: its value is unknown at assembly |
| 2256 | time so it has section @emph{undefined}. |
| 2257 | |
| 2258 | By analogy the word @emph{section} is used to describe groups of sections in |
| 2259 | the linked program. @code{@value{LD}} puts all partial programs' text |
| 2260 | sections in contiguous addresses in the linked program. It is |
| 2261 | customary to refer to the @emph{text section} of a program, meaning all |
| 2262 | the addresses of all partial programs' text sections. Likewise for |
| 2263 | data and bss sections. |
| 2264 | |
| 2265 | Some sections are manipulated by @code{@value{LD}}; others are invented for |
| 2266 | use of @code{@value{AS}} and have no meaning except during assembly. |
| 2267 | |
| 2268 | @node Ld Sections |
| 2269 | @section Linker Sections |
| 2270 | @code{@value{LD}} deals with just four kinds of sections, summarized below. |
| 2271 | |
| 2272 | @table @strong |
| 2273 | |
| 2274 | @ifset COFF |
| 2275 | @cindex named sections |
| 2276 | @cindex sections, named |
| 2277 | @item named sections |
| 2278 | @end ifset |
| 2279 | @ifset aout-bout |
| 2280 | @cindex text section |
| 2281 | @cindex data section |
| 2282 | @itemx text section |
| 2283 | @itemx data section |
| 2284 | @end ifset |
| 2285 | These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as |
| 2286 | separate but equal sections. Anything you can say of one section is |
| 2287 | true another. |
| 2288 | @ifset aout-bout |
| 2289 | When the program is running, however, it is |
| 2290 | customary for the text section to be unalterable. The |
| 2291 | text section is often shared among processes: it contains |
| 2292 | instructions, constants and the like. The data section of a running |
| 2293 | program is usually alterable: for example, C variables would be stored |
| 2294 | in the data section. |
| 2295 | @end ifset |
| 2296 | |
| 2297 | @cindex bss section |
| 2298 | @item bss section |
| 2299 | This section contains zeroed bytes when your program begins running. It |
| 2300 | is used to hold unitialized variables or common storage. The length of |
| 2301 | each partial program's bss section is important, but because it starts |
| 2302 | out containing zeroed bytes there is no need to store explicit zero |
| 2303 | bytes in the object file. The bss section was invented to eliminate |
| 2304 | those explicit zeros from object files. |
| 2305 | |
| 2306 | @cindex absolute section |
| 2307 | @item absolute section |
| 2308 | Address 0 of this section is always ``relocated'' to runtime address 0. |
| 2309 | This is useful if you want to refer to an address that @code{@value{LD}} must |
| 2310 | not change when relocating. In this sense we speak of absolute |
| 2311 | addresses being ``unrelocatable'': they do not change during relocation. |
| 2312 | |
| 2313 | @cindex undefined section |
| 2314 | @item undefined section |
| 2315 | This ``section'' is a catch-all for address references to objects not in |
| 2316 | the preceding sections. |
| 2317 | @c FIXME: ref to some other doc on obj-file formats could go here. |
| 2318 | @end table |
| 2319 | |
| 2320 | @cindex relocation example |
| 2321 | An idealized example of three relocatable sections follows. |
| 2322 | @ifset COFF |
| 2323 | The example uses the traditional section names @samp{.text} and @samp{.data}. |
| 2324 | @end ifset |
| 2325 | Memory addresses are on the horizontal axis. |
| 2326 | |
| 2327 | @c TEXI2ROFF-KILL |
| 2328 | @ifinfo |
| 2329 | @c END TEXI2ROFF-KILL |
| 2330 | @smallexample |
| 2331 | +-----+----+--+ |
| 2332 | partial program # 1: |ttttt|dddd|00| |
| 2333 | +-----+----+--+ |
| 2334 | |
| 2335 | text data bss |
| 2336 | seg. seg. seg. |
| 2337 | |
| 2338 | +---+---+---+ |
| 2339 | partial program # 2: |TTT|DDD|000| |
| 2340 | +---+---+---+ |
| 2341 | |
| 2342 | +--+---+-----+--+----+---+-----+~~ |
| 2343 | linked program: | |TTT|ttttt| |dddd|DDD|00000| |
| 2344 | +--+---+-----+--+----+---+-----+~~ |
| 2345 | |
| 2346 | addresses: 0 @dots{} |
| 2347 | @end smallexample |
| 2348 | @c TEXI2ROFF-KILL |
| 2349 | @end ifinfo |
| 2350 | @need 5000 |
| 2351 | @tex |
| 2352 | |
| 2353 | \line{\it Partial program \#1: \hfil} |
| 2354 | \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil} |
| 2355 | \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil} |
| 2356 | |
| 2357 | \line{\it Partial program \#2: \hfil} |
| 2358 | \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil} |
| 2359 | \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil} |
| 2360 | |
| 2361 | \line{\it linked program: \hfil} |
| 2362 | \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil} |
| 2363 | \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt |
| 2364 | ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt |
| 2365 | DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil} |
| 2366 | |
| 2367 | \line{\it addresses: \hfil} |
| 2368 | \line{0\dots\hfil} |
| 2369 | |
| 2370 | @end tex |
| 2371 | @c END TEXI2ROFF-KILL |
| 2372 | |
| 2373 | @node As Sections |
| 2374 | @section Assembler Internal Sections |
| 2375 | |
| 2376 | @cindex internal assembler sections |
| 2377 | @cindex sections in messages, internal |
| 2378 | These sections are meant only for the internal use of @code{@value{AS}}. They |
| 2379 | have no meaning at run-time. You do not really need to know about these |
| 2380 | sections for most purposes; but they can be mentioned in @code{@value{AS}} |
| 2381 | warning messages, so it might be helpful to have an idea of their |
| 2382 | meanings to @code{@value{AS}}. These sections are used to permit the |
| 2383 | value of every expression in your assembly language program to be a |
| 2384 | section-relative address. |
| 2385 | |
| 2386 | @table @b |
| 2387 | @cindex assembler internal logic error |
| 2388 | @item ASSEMBLER-INTERNAL-LOGIC-ERROR! |
| 2389 | An internal assembler logic error has been found. This means there is a |
| 2390 | bug in the assembler. |
| 2391 | |
| 2392 | @cindex expr (internal section) |
| 2393 | @item expr section |
| 2394 | The assembler stores complex expression internally as combinations of |
| 2395 | symbols. When it needs to represent an expression as a symbol, it puts |
| 2396 | it in the expr section. |
| 2397 | @c FIXME item debug |
| 2398 | @c FIXME item transfer[t] vector preload |
| 2399 | @c FIXME item transfer[t] vector postload |
| 2400 | @c FIXME item register |
| 2401 | @end table |
| 2402 | |
| 2403 | @node Sub-Sections |
| 2404 | @section Sub-Sections |
| 2405 | |
| 2406 | @cindex numbered subsections |
| 2407 | @cindex grouping data |
| 2408 | @ifset aout-bout |
| 2409 | Assembled bytes |
| 2410 | @ifset COFF |
| 2411 | conventionally |
| 2412 | @end ifset |
| 2413 | fall into two sections: text and data. |
| 2414 | @end ifset |
| 2415 | You may have separate groups of |
| 2416 | @ifset GENERIC |
| 2417 | data in named sections |
| 2418 | @end ifset |
| 2419 | @ifclear GENERIC |
| 2420 | @ifclear aout-bout |
| 2421 | data in named sections |
| 2422 | @end ifclear |
| 2423 | @ifset aout-bout |
| 2424 | text or data |
| 2425 | @end ifset |
| 2426 | @end ifclear |
| 2427 | that you want to end up near to each other in the object file, even though they |
| 2428 | are not contiguous in the assembler source. @code{@value{AS}} allows you to |
| 2429 | use @dfn{subsections} for this purpose. Within each section, there can be |
| 2430 | numbered subsections with values from 0 to 8192. Objects assembled into the |
| 2431 | same subsection go into the object file together with other objects in the same |
| 2432 | subsection. For example, a compiler might want to store constants in the text |
| 2433 | section, but might not want to have them interspersed with the program being |
| 2434 | assembled. In this case, the compiler could issue a @samp{.text 0} before each |
| 2435 | section of code being output, and a @samp{.text 1} before each group of |
| 2436 | constants being output. |
| 2437 | |
| 2438 | Subsections are optional. If you do not use subsections, everything |
| 2439 | goes in subsection number zero. |
| 2440 | |
| 2441 | @ifset GENERIC |
| 2442 | Each subsection is zero-padded up to a multiple of four bytes. |
| 2443 | (Subsections may be padded a different amount on different flavors |
| 2444 | of @code{@value{AS}}.) |
| 2445 | @end ifset |
| 2446 | @ifclear GENERIC |
| 2447 | @ifset H8 |
| 2448 | On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word |
| 2449 | boundary (two bytes). |
| 2450 | The same is true on the Hitachi SH. |
| 2451 | @end ifset |
| 2452 | @ifset I960 |
| 2453 | @c FIXME section padding (alignment)? |
| 2454 | @c Rich Pixley says padding here depends on target obj code format; that |
| 2455 | @c doesn't seem particularly useful to say without further elaboration, |
| 2456 | @c so for now I say nothing about it. If this is a generic BFD issue, |
| 2457 | @c these paragraphs might need to vanish from this manual, and be |
| 2458 | @c discussed in BFD chapter of binutils (or some such). |
| 2459 | @end ifset |
| 2460 | @ifset A29K |
| 2461 | On the AMD 29K family, no particular padding is added to section or |
| 2462 | subsection sizes; @value{AS} forces no alignment on this platform. |
| 2463 | @end ifset |
| 2464 | @end ifclear |
| 2465 | |
| 2466 | Subsections appear in your object file in numeric order, lowest numbered |
| 2467 | to highest. (All this to be compatible with other people's assemblers.) |
| 2468 | The object file contains no representation of subsections; @code{@value{LD}} and |
| 2469 | other programs that manipulate object files see no trace of them. |
| 2470 | They just see all your text subsections as a text section, and all your |
| 2471 | data subsections as a data section. |
| 2472 | |
| 2473 | To specify which subsection you want subsequent statements assembled |
| 2474 | into, use a numeric argument to specify it, in a @samp{.text |
| 2475 | @var{expression}} or a @samp{.data @var{expression}} statement. |
| 2476 | @ifset COFF |
| 2477 | @ifset GENERIC |
| 2478 | When generating COFF output, you |
| 2479 | @end ifset |
| 2480 | @ifclear GENERIC |
| 2481 | You |
| 2482 | @end ifclear |
| 2483 | can also use an extra subsection |
| 2484 | argument with arbitrary named sections: @samp{.section @var{name}, |
| 2485 | @var{expression}}. |
| 2486 | @end ifset |
| 2487 | @var{Expression} should be an absolute expression. |
| 2488 | (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0} |
| 2489 | is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly |
| 2490 | begins in @code{text 0}. For instance: |
| 2491 | @smallexample |
| 2492 | .text 0 # The default subsection is text 0 anyway. |
| 2493 | .ascii "This lives in the first text subsection. *" |
| 2494 | .text 1 |
| 2495 | .ascii "But this lives in the second text subsection." |
| 2496 | .data 0 |
| 2497 | .ascii "This lives in the data section," |
| 2498 | .ascii "in the first data subsection." |
| 2499 | .text 0 |
| 2500 | .ascii "This lives in the first text section," |
| 2501 | .ascii "immediately following the asterisk (*)." |
| 2502 | @end smallexample |
| 2503 | |
| 2504 | Each section has a @dfn{location counter} incremented by one for every byte |
| 2505 | assembled into that section. Because subsections are merely a convenience |
| 2506 | restricted to @code{@value{AS}} there is no concept of a subsection location |
| 2507 | counter. There is no way to directly manipulate a location counter---but the |
| 2508 | @code{.align} directive changes it, and any label definition captures its |
| 2509 | current value. The location counter of the section where statements are being |
| 2510 | assembled is said to be the @dfn{active} location counter. |
| 2511 | |
| 2512 | @node bss |
| 2513 | @section bss Section |
| 2514 | |
| 2515 | @cindex bss section |
| 2516 | @cindex common variable storage |
| 2517 | The bss section is used for local common variable storage. |
| 2518 | You may allocate address space in the bss section, but you may |
| 2519 | not dictate data to load into it before your program executes. When |
| 2520 | your program starts running, all the contents of the bss |
| 2521 | section are zeroed bytes. |
| 2522 | |
| 2523 | The @code{.lcomm} pseudo-op defines a symbol in the bss section; see |
| 2524 | @ref{Lcomm,,@code{.lcomm}}. |
| 2525 | |
| 2526 | The @code{.comm} pseudo-op may be used to declare a common symbol, which is |
| 2527 | another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}. |
| 2528 | |
| 2529 | @ifset GENERIC |
| 2530 | When assembling for a target which supports multiple sections, such as ELF or |
| 2531 | COFF, you may switch into the @code{.bss} section and define symbols as usual; |
| 2532 | see @ref{Section,,@code{.section}}. You may only assemble zero values into the |
| 2533 | section. Typically the section will only contain symbol definitions and |
| 2534 | @code{.skip} directives (@pxref{Skip,,@code{.skip}}). |
| 2535 | @end ifset |
| 2536 | |
| 2537 | @node Symbols |
| 2538 | @chapter Symbols |
| 2539 | |
| 2540 | @cindex symbols |
| 2541 | Symbols are a central concept: the programmer uses symbols to name |
| 2542 | things, the linker uses symbols to link, and the debugger uses symbols |
| 2543 | to debug. |
| 2544 | |
| 2545 | @quotation |
| 2546 | @cindex debuggers, and symbol order |
| 2547 | @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in |
| 2548 | the same order they were declared. This may break some debuggers. |
| 2549 | @end quotation |
| 2550 | |
| 2551 | @menu |
| 2552 | * Labels:: Labels |
| 2553 | * Setting Symbols:: Giving Symbols Other Values |
| 2554 | * Symbol Names:: Symbol Names |
| 2555 | * Dot:: The Special Dot Symbol |
| 2556 | * Symbol Attributes:: Symbol Attributes |
| 2557 | @end menu |
| 2558 | |
| 2559 | @node Labels |
| 2560 | @section Labels |
| 2561 | |
| 2562 | @cindex labels |
| 2563 | A @dfn{label} is written as a symbol immediately followed by a colon |
| 2564 | @samp{:}. The symbol then represents the current value of the |
| 2565 | active location counter, and is, for example, a suitable instruction |
| 2566 | operand. You are warned if you use the same symbol to represent two |
| 2567 | different locations: the first definition overrides any other |
| 2568 | definitions. |
| 2569 | |
| 2570 | @ifset HPPA |
| 2571 | On the HPPA, the usual form for a label need not be immediately followed by a |
| 2572 | colon, but instead must start in column zero. Only one label may be defined on |
| 2573 | a single line. To work around this, the HPPA version of @code{@value{AS}} also |
| 2574 | provides a special directive @code{.label} for defining labels more flexibly. |
| 2575 | @end ifset |
| 2576 | |
| 2577 | @node Setting Symbols |
| 2578 | @section Giving Symbols Other Values |
| 2579 | |
| 2580 | @cindex assigning values to symbols |
| 2581 | @cindex symbol values, assigning |
| 2582 | A symbol can be given an arbitrary value by writing a symbol, followed |
| 2583 | by an equals sign @samp{=}, followed by an expression |
| 2584 | (@pxref{Expressions}). This is equivalent to using the @code{.set} |
| 2585 | directive. @xref{Set,,@code{.set}}. |
| 2586 | |
| 2587 | @node Symbol Names |
| 2588 | @section Symbol Names |
| 2589 | |
| 2590 | @cindex symbol names |
| 2591 | @cindex names, symbol |
| 2592 | @ifclear SPECIAL-SYMS |
| 2593 | Symbol names begin with a letter or with one of @samp{._}. On most |
| 2594 | machines, you can also use @code{$} in symbol names; exceptions are |
| 2595 | noted in @ref{Machine Dependencies}. That character may be followed by any |
| 2596 | string of digits, letters, dollar signs (unless otherwise noted in |
| 2597 | @ref{Machine Dependencies}), and underscores. |
| 2598 | @end ifclear |
| 2599 | @ifset A29K |
| 2600 | For the AMD 29K family, @samp{?} is also allowed in the |
| 2601 | body of a symbol name, though not at its beginning. |
| 2602 | @end ifset |
| 2603 | |
| 2604 | @ifset SPECIAL-SYMS |
| 2605 | @ifset H8 |
| 2606 | Symbol names begin with a letter or with one of @samp{._}. On the |
| 2607 | Hitachi SH or the |
| 2608 | H8/500, you can also use @code{$} in symbol names. That character may |
| 2609 | be followed by any string of digits, letters, dollar signs (save on the |
| 2610 | H8/300), and underscores. |
| 2611 | @end ifset |
| 2612 | @end ifset |
| 2613 | |
| 2614 | Case of letters is significant: @code{foo} is a different symbol name |
| 2615 | than @code{Foo}. |
| 2616 | |
| 2617 | Each symbol has exactly one name. Each name in an assembly language program |
| 2618 | refers to exactly one symbol. You may use that symbol name any number of times |
| 2619 | in a program. |
| 2620 | |
| 2621 | @subheading Local Symbol Names |
| 2622 | |
| 2623 | @cindex local symbol names |
| 2624 | @cindex symbol names, local |
| 2625 | @cindex temporary symbol names |
| 2626 | @cindex symbol names, temporary |
| 2627 | Local symbols help compilers and programmers use names temporarily. |
| 2628 | There are ten local symbol names, which are re-used throughout the |
| 2629 | program. You may refer to them using the names @samp{0} @samp{1} |
| 2630 | @dots{} @samp{9}. To define a local symbol, write a label of the form |
| 2631 | @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most |
| 2632 | recent previous definition of that symbol write @samp{@b{N}b}, using the |
| 2633 | same digit as when you defined the label. To refer to the next |
| 2634 | definition of a local label, write @samp{@b{N}f}---where @b{N} gives you |
| 2635 | a choice of 10 forward references. The @samp{b} stands for |
| 2636 | ``backwards'' and the @samp{f} stands for ``forwards''. |
| 2637 | |
| 2638 | Local symbols are not emitted by the current @sc{gnu} C compiler. |
| 2639 | |
| 2640 | There is no restriction on how you can use these labels, but |
| 2641 | remember that at any point in the assembly you can refer to at most |
| 2642 | 10 prior local labels and to at most 10 forward local labels. |
| 2643 | |
| 2644 | Local symbol names are only a notation device. They are immediately |
| 2645 | transformed into more conventional symbol names before the assembler |
| 2646 | uses them. The symbol names stored in the symbol table, appearing in |
| 2647 | error messages and optionally emitted to the object file have these |
| 2648 | parts: |
| 2649 | |
| 2650 | @table @code |
| 2651 | @item L |
| 2652 | All local labels begin with @samp{L}. Normally both @code{@value{AS}} and |
| 2653 | @code{@value{LD}} forget symbols that start with @samp{L}. These labels are |
| 2654 | used for symbols you are never intended to see. If you use the |
| 2655 | @samp{-L} option then @code{@value{AS}} retains these symbols in the |
| 2656 | object file. If you also instruct @code{@value{LD}} to retain these symbols, |
| 2657 | you may use them in debugging. |
| 2658 | |
| 2659 | @item @var{digit} |
| 2660 | If the label is written @samp{0:} then the digit is @samp{0}. |
| 2661 | If the label is written @samp{1:} then the digit is @samp{1}. |
| 2662 | And so on up through @samp{9:}. |
| 2663 | |
| 2664 | @item @kbd{C-A} |
| 2665 | This unusual character is included so you do not accidentally invent |
| 2666 | a symbol of the same name. The character has ASCII value |
| 2667 | @samp{\001}. |
| 2668 | |
| 2669 | @item @emph{ordinal number} |
| 2670 | This is a serial number to keep the labels distinct. The first |
| 2671 | @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the |
| 2672 | number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:} |
| 2673 | through @samp{9:}. |
| 2674 | @end table |
| 2675 | |
| 2676 | For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th |
| 2677 | @code{3:} is named @code{L3@kbd{C-A}44}. |
| 2678 | |
| 2679 | @node Dot |
| 2680 | @section The Special Dot Symbol |
| 2681 | |
| 2682 | @cindex dot (symbol) |
| 2683 | @cindex @code{.} (symbol) |
| 2684 | @cindex current address |
| 2685 | @cindex location counter |
| 2686 | The special symbol @samp{.} refers to the current address that |
| 2687 | @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin: |
| 2688 | .long .} defines @code{melvin} to contain its own address. |
| 2689 | Assigning a value to @code{.} is treated the same as a @code{.org} |
| 2690 | directive. Thus, the expression @samp{.=.+4} is the same as saying |
| 2691 | @ifclear no-space-dir |
| 2692 | @samp{.space 4}. |
| 2693 | @end ifclear |
| 2694 | @ifset no-space-dir |
| 2695 | @ifset A29K |
| 2696 | @samp{.block 4}. |
| 2697 | @end ifset |
| 2698 | @end ifset |
| 2699 | |
| 2700 | @node Symbol Attributes |
| 2701 | @section Symbol Attributes |
| 2702 | |
| 2703 | @cindex symbol attributes |
| 2704 | @cindex attributes, symbol |
| 2705 | Every symbol has, as well as its name, the attributes ``Value'' and |
| 2706 | ``Type''. Depending on output format, symbols can also have auxiliary |
| 2707 | attributes. |
| 2708 | @ifset INTERNALS |
| 2709 | The detailed definitions are in @file{a.out.h}. |
| 2710 | @end ifset |
| 2711 | |
| 2712 | If you use a symbol without defining it, @code{@value{AS}} assumes zero for |
| 2713 | all these attributes, and probably won't warn you. This makes the |
| 2714 | symbol an externally defined symbol, which is generally what you |
| 2715 | would want. |
| 2716 | |
| 2717 | @menu |
| 2718 | * Symbol Value:: Value |
| 2719 | * Symbol Type:: Type |
| 2720 | @ifset aout-bout |
| 2721 | @ifset GENERIC |
| 2722 | * a.out Symbols:: Symbol Attributes: @code{a.out} |
| 2723 | @end ifset |
| 2724 | @ifclear GENERIC |
| 2725 | @ifclear BOUT |
| 2726 | * a.out Symbols:: Symbol Attributes: @code{a.out} |
| 2727 | @end ifclear |
| 2728 | @ifset BOUT |
| 2729 | * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out} |
| 2730 | @end ifset |
| 2731 | @end ifclear |
| 2732 | @end ifset |
| 2733 | @ifset COFF |
| 2734 | * COFF Symbols:: Symbol Attributes for COFF |
| 2735 | @end ifset |
| 2736 | @ifset SOM |
| 2737 | * SOM Symbols:: Symbol Attributes for SOM |
| 2738 | @end ifset |
| 2739 | @end menu |
| 2740 | |
| 2741 | @node Symbol Value |
| 2742 | @subsection Value |
| 2743 | |
| 2744 | @cindex value of a symbol |
| 2745 | @cindex symbol value |
| 2746 | The value of a symbol is (usually) 32 bits. For a symbol which labels a |
| 2747 | location in the text, data, bss or absolute sections the value is the |
| 2748 | number of addresses from the start of that section to the label. |
| 2749 | Naturally for text, data and bss sections the value of a symbol changes |
| 2750 | as @code{@value{LD}} changes section base addresses during linking. Absolute |
| 2751 | symbols' values do not change during linking: that is why they are |
| 2752 | called absolute. |
| 2753 | |
| 2754 | The value of an undefined symbol is treated in a special way. If it is |
| 2755 | 0 then the symbol is not defined in this assembler source file, and |
| 2756 | @code{@value{LD}} tries to determine its value from other files linked into the |
| 2757 | same program. You make this kind of symbol simply by mentioning a symbol |
| 2758 | name without defining it. A non-zero value represents a @code{.comm} |
| 2759 | common declaration. The value is how much common storage to reserve, in |
| 2760 | bytes (addresses). The symbol refers to the first address of the |
| 2761 | allocated storage. |
| 2762 | |
| 2763 | @node Symbol Type |
| 2764 | @subsection Type |
| 2765 | |
| 2766 | @cindex type of a symbol |
| 2767 | @cindex symbol type |
| 2768 | The type attribute of a symbol contains relocation (section) |
| 2769 | information, any flag settings indicating that a symbol is external, and |
| 2770 | (optionally), other information for linkers and debuggers. The exact |
| 2771 | format depends on the object-code output format in use. |
| 2772 | |
| 2773 | @ifset aout-bout |
| 2774 | @ifclear GENERIC |
| 2775 | @ifset BOUT |
| 2776 | @c The following avoids a "widow" subsection title. @group would be |
| 2777 | @c better if it were available outside examples. |
| 2778 | @need 1000 |
| 2779 | @node a.out Symbols |
| 2780 | @subsection Symbol Attributes: @code{a.out}, @code{b.out} |
| 2781 | |
| 2782 | @cindex @code{b.out} symbol attributes |
| 2783 | @cindex symbol attributes, @code{b.out} |
| 2784 | These symbol attributes appear only when @code{@value{AS}} is configured for |
| 2785 | one of the Berkeley-descended object output formats---@code{a.out} or |
| 2786 | @code{b.out}. |
| 2787 | |
| 2788 | @end ifset |
| 2789 | @ifclear BOUT |
| 2790 | @node a.out Symbols |
| 2791 | @subsection Symbol Attributes: @code{a.out} |
| 2792 | |
| 2793 | @cindex @code{a.out} symbol attributes |
| 2794 | @cindex symbol attributes, @code{a.out} |
| 2795 | |
| 2796 | @end ifclear |
| 2797 | @end ifclear |
| 2798 | @ifset GENERIC |
| 2799 | @node a.out Symbols |
| 2800 | @subsection Symbol Attributes: @code{a.out} |
| 2801 | |
| 2802 | @cindex @code{a.out} symbol attributes |
| 2803 | @cindex symbol attributes, @code{a.out} |
| 2804 | |
| 2805 | @end ifset |
| 2806 | @menu |
| 2807 | * Symbol Desc:: Descriptor |
| 2808 | * Symbol Other:: Other |
| 2809 | @end menu |
| 2810 | |
| 2811 | @node Symbol Desc |
| 2812 | @subsubsection Descriptor |
| 2813 | |
| 2814 | @cindex descriptor, of @code{a.out} symbol |
| 2815 | This is an arbitrary 16-bit value. You may establish a symbol's |
| 2816 | descriptor value by using a @code{.desc} statement |
| 2817 | (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to |
| 2818 | @code{@value{AS}}. |
| 2819 | |
| 2820 | @node Symbol Other |
| 2821 | @subsubsection Other |
| 2822 | |
| 2823 | @cindex other attribute, of @code{a.out} symbol |
| 2824 | This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}. |
| 2825 | @end ifset |
| 2826 | |
| 2827 | @ifset COFF |
| 2828 | @node COFF Symbols |
| 2829 | @subsection Symbol Attributes for COFF |
| 2830 | |
| 2831 | @cindex COFF symbol attributes |
| 2832 | @cindex symbol attributes, COFF |
| 2833 | |
| 2834 | The COFF format supports a multitude of auxiliary symbol attributes; |
| 2835 | like the primary symbol attributes, they are set between @code{.def} and |
| 2836 | @code{.endef} directives. |
| 2837 | |
| 2838 | @subsubsection Primary Attributes |
| 2839 | |
| 2840 | @cindex primary attributes, COFF symbols |
| 2841 | The symbol name is set with @code{.def}; the value and type, |
| 2842 | respectively, with @code{.val} and @code{.type}. |
| 2843 | |
| 2844 | @subsubsection Auxiliary Attributes |
| 2845 | |
| 2846 | @cindex auxiliary attributes, COFF symbols |
| 2847 | The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl}, |
| 2848 | @code{.size}, and @code{.tag} can generate auxiliary symbol table |
| 2849 | information for COFF. |
| 2850 | @end ifset |
| 2851 | |
| 2852 | @ifset SOM |
| 2853 | @node SOM Symbols |
| 2854 | @subsection Symbol Attributes for SOM |
| 2855 | |
| 2856 | @cindex SOM symbol attributes |
| 2857 | @cindex symbol attributes, SOM |
| 2858 | |
| 2859 | The SOM format for the HPPA supports a multitude of symbol attributes set with |
| 2860 | the @code{.EXPORT} and @code{.IMPORT} directives. |
| 2861 | |
| 2862 | The attributes are described in @cite{HP9000 Series 800 Assembly |
| 2863 | Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and |
| 2864 | @code{EXPORT} assembler directive documentation. |
| 2865 | @end ifset |
| 2866 | |
| 2867 | @node Expressions |
| 2868 | @chapter Expressions |
| 2869 | |
| 2870 | @cindex expressions |
| 2871 | @cindex addresses |
| 2872 | @cindex numeric values |
| 2873 | An @dfn{expression} specifies an address or numeric value. |
| 2874 | Whitespace may precede and/or follow an expression. |
| 2875 | |
| 2876 | The result of an expression must be an absolute number, or else an offset into |
| 2877 | a particular section. If an expression is not absolute, and there is not |
| 2878 | enough information when @code{@value{AS}} sees the expression to know its |
| 2879 | section, a second pass over the source program might be necessary to interpret |
| 2880 | the expression---but the second pass is currently not implemented. |
| 2881 | @code{@value{AS}} aborts with an error message in this situation. |
| 2882 | |
| 2883 | @menu |
| 2884 | * Empty Exprs:: Empty Expressions |
| 2885 | * Integer Exprs:: Integer Expressions |
| 2886 | @end menu |
| 2887 | |
| 2888 | @node Empty Exprs |
| 2889 | @section Empty Expressions |
| 2890 | |
| 2891 | @cindex empty expressions |
| 2892 | @cindex expressions, empty |
| 2893 | An empty expression has no value: it is just whitespace or null. |
| 2894 | Wherever an absolute expression is required, you may omit the |
| 2895 | expression, and @code{@value{AS}} assumes a value of (absolute) 0. This |
| 2896 | is compatible with other assemblers. |
| 2897 | |
| 2898 | @node Integer Exprs |
| 2899 | @section Integer Expressions |
| 2900 | |
| 2901 | @cindex integer expressions |
| 2902 | @cindex expressions, integer |
| 2903 | An @dfn{integer expression} is one or more @emph{arguments} delimited |
| 2904 | by @emph{operators}. |
| 2905 | |
| 2906 | @menu |
| 2907 | * Arguments:: Arguments |
| 2908 | * Operators:: Operators |
| 2909 | * Prefix Ops:: Prefix Operators |
| 2910 | * Infix Ops:: Infix Operators |
| 2911 | @end menu |
| 2912 | |
| 2913 | @node Arguments |
| 2914 | @subsection Arguments |
| 2915 | |
| 2916 | @cindex expression arguments |
| 2917 | @cindex arguments in expressions |
| 2918 | @cindex operands in expressions |
| 2919 | @cindex arithmetic operands |
| 2920 | @dfn{Arguments} are symbols, numbers or subexpressions. In other |
| 2921 | contexts arguments are sometimes called ``arithmetic operands''. In |
| 2922 | this manual, to avoid confusing them with the ``instruction operands'' of |
| 2923 | the machine language, we use the term ``argument'' to refer to parts of |
| 2924 | expressions only, reserving the word ``operand'' to refer only to machine |
| 2925 | instruction operands. |
| 2926 | |
| 2927 | Symbols are evaluated to yield @{@var{section} @var{NNN}@} where |
| 2928 | @var{section} is one of text, data, bss, absolute, |
| 2929 | or undefined. @var{NNN} is a signed, 2's complement 32 bit |
| 2930 | integer. |
| 2931 | |
| 2932 | Numbers are usually integers. |
| 2933 | |
| 2934 | A number can be a flonum or bignum. In this case, you are warned |
| 2935 | that only the low order 32 bits are used, and @code{@value{AS}} pretends |
| 2936 | these 32 bits are an integer. You may write integer-manipulating |
| 2937 | instructions that act on exotic constants, compatible with other |
| 2938 | assemblers. |
| 2939 | |
| 2940 | @cindex subexpressions |
| 2941 | Subexpressions are a left parenthesis @samp{(} followed by an integer |
| 2942 | expression, followed by a right parenthesis @samp{)}; or a prefix |
| 2943 | operator followed by an argument. |
| 2944 | |
| 2945 | @node Operators |
| 2946 | @subsection Operators |
| 2947 | |
| 2948 | @cindex operators, in expressions |
| 2949 | @cindex arithmetic functions |
| 2950 | @cindex functions, in expressions |
| 2951 | @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix |
| 2952 | operators are followed by an argument. Infix operators appear |
| 2953 | between their arguments. Operators may be preceded and/or followed by |
| 2954 | whitespace. |
| 2955 | |
| 2956 | @node Prefix Ops |
| 2957 | @subsection Prefix Operator |
| 2958 | |
| 2959 | @cindex prefix operators |
| 2960 | @code{@value{AS}} has the following @dfn{prefix operators}. They each take |
| 2961 | one argument, which must be absolute. |
| 2962 | |
| 2963 | @c the tex/end tex stuff surrounding this small table is meant to make |
| 2964 | @c it align, on the printed page, with the similar table in the next |
| 2965 | @c section (which is inside an enumerate). |
| 2966 | @tex |
| 2967 | \global\advance\leftskip by \itemindent |
| 2968 | @end tex |
| 2969 | |
| 2970 | @table @code |
| 2971 | @item - |
| 2972 | @dfn{Negation}. Two's complement negation. |
| 2973 | @item ~ |
| 2974 | @dfn{Complementation}. Bitwise not. |
| 2975 | @end table |
| 2976 | |
| 2977 | @tex |
| 2978 | \global\advance\leftskip by -\itemindent |
| 2979 | @end tex |
| 2980 | |
| 2981 | @node Infix Ops |
| 2982 | @subsection Infix Operators |
| 2983 | |
| 2984 | @cindex infix operators |
| 2985 | @cindex operators, permitted arguments |
| 2986 | @dfn{Infix operators} take two arguments, one on either side. Operators |
| 2987 | have precedence, but operations with equal precedence are performed left |
| 2988 | to right. Apart from @code{+} or @code{-}, both arguments must be |
| 2989 | absolute, and the result is absolute. |
| 2990 | |
| 2991 | @enumerate |
| 2992 | @cindex operator precedence |
| 2993 | @cindex precedence of operators |
| 2994 | |
| 2995 | @item |
| 2996 | Highest Precedence |
| 2997 | |
| 2998 | @table @code |
| 2999 | @item * |
| 3000 | @dfn{Multiplication}. |
| 3001 | |
| 3002 | @item / |
| 3003 | @dfn{Division}. Truncation is the same as the C operator @samp{/} |
| 3004 | |
| 3005 | @item % |
| 3006 | @dfn{Remainder}. |
| 3007 | |
| 3008 | @item < |
| 3009 | @itemx << |
| 3010 | @dfn{Shift Left}. Same as the C operator @samp{<<}. |
| 3011 | |
| 3012 | @item > |
| 3013 | @itemx >> |
| 3014 | @dfn{Shift Right}. Same as the C operator @samp{>>}. |
| 3015 | @end table |
| 3016 | |
| 3017 | @item |
| 3018 | Intermediate precedence |
| 3019 | |
| 3020 | @table @code |
| 3021 | @item | |
| 3022 | |
| 3023 | @dfn{Bitwise Inclusive Or}. |
| 3024 | |
| 3025 | @item & |
| 3026 | @dfn{Bitwise And}. |
| 3027 | |
| 3028 | @item ^ |
| 3029 | @dfn{Bitwise Exclusive Or}. |
| 3030 | |
| 3031 | @item ! |
| 3032 | @dfn{Bitwise Or Not}. |
| 3033 | @end table |
| 3034 | |
| 3035 | @item |
| 3036 | Lowest Precedence |
| 3037 | |
| 3038 | @table @code |
| 3039 | @cindex addition, permitted arguments |
| 3040 | @cindex plus, permitted arguments |
| 3041 | @cindex arguments for addition |
| 3042 | @item + |
| 3043 | @dfn{Addition}. If either argument is absolute, the result has the section of |
| 3044 | the other argument. You may not add together arguments from different |
| 3045 | sections. |
| 3046 | |
| 3047 | @cindex subtraction, permitted arguments |
| 3048 | @cindex minus, permitted arguments |
| 3049 | @cindex arguments for subtraction |
| 3050 | @item - |
| 3051 | @dfn{Subtraction}. If the right argument is absolute, the |
| 3052 | result has the section of the left argument. |
| 3053 | If both arguments are in the same section, the result is absolute. |
| 3054 | You may not subtract arguments from different sections. |
| 3055 | @c FIXME is there still something useful to say about undefined - undefined ? |
| 3056 | @end table |
| 3057 | @end enumerate |
| 3058 | |
| 3059 | In short, it's only meaningful to add or subtract the @emph{offsets} in an |
| 3060 | address; you can only have a defined section in one of the two arguments. |
| 3061 | |
| 3062 | @node Pseudo Ops |
| 3063 | @chapter Assembler Directives |
| 3064 | |
| 3065 | @cindex directives, machine independent |
| 3066 | @cindex pseudo-ops, machine independent |
| 3067 | @cindex machine independent directives |
| 3068 | All assembler directives have names that begin with a period (@samp{.}). |
| 3069 | The rest of the name is letters, usually in lower case. |
| 3070 | |
| 3071 | This chapter discusses directives that are available regardless of the |
| 3072 | target machine configuration for the @sc{gnu} assembler. |
| 3073 | @ifset GENERIC |
| 3074 | Some machine configurations provide additional directives. |
| 3075 | @xref{Machine Dependencies}. |
| 3076 | @end ifset |
| 3077 | @ifclear GENERIC |
| 3078 | @ifset machine-directives |
| 3079 | @xref{Machine Dependencies} for additional directives. |
| 3080 | @end ifset |
| 3081 | @end ifclear |
| 3082 | |
| 3083 | @menu |
| 3084 | * Abort:: @code{.abort} |
| 3085 | @ifset COFF |
| 3086 | * ABORT:: @code{.ABORT} |
| 3087 | @end ifset |
| 3088 | |
| 3089 | * Align:: @code{.align @var{abs-expr} , @var{abs-expr}} |
| 3090 | * Ascii:: @code{.ascii "@var{string}"}@dots{} |
| 3091 | * Asciz:: @code{.asciz "@var{string}"}@dots{} |
| 3092 | * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}} |
| 3093 | * Byte:: @code{.byte @var{expressions}} |
| 3094 | * Comm:: @code{.comm @var{symbol} , @var{length} } |
| 3095 | * Data:: @code{.data @var{subsection}} |
| 3096 | @ifset COFF |
| 3097 | * Def:: @code{.def @var{name}} |
| 3098 | @end ifset |
| 3099 | @ifset aout-bout |
| 3100 | * Desc:: @code{.desc @var{symbol}, @var{abs-expression}} |
| 3101 | @end ifset |
| 3102 | @ifset COFF |
| 3103 | * Dim:: @code{.dim} |
| 3104 | @end ifset |
| 3105 | |
| 3106 | * Double:: @code{.double @var{flonums}} |
| 3107 | * Eject:: @code{.eject} |
| 3108 | * Else:: @code{.else} |
| 3109 | * End:: @code{.end} |
| 3110 | @ifset COFF |
| 3111 | * Endef:: @code{.endef} |
| 3112 | @end ifset |
| 3113 | |
| 3114 | * Endfunc:: @code{.endfunc} |
| 3115 | * Endif:: @code{.endif} |
| 3116 | * Equ:: @code{.equ @var{symbol}, @var{expression}} |
| 3117 | * Equiv:: @code{.equiv @var{symbol}, @var{expression}} |
| 3118 | * Err:: @code{.err} |
| 3119 | * Exitm:: @code{.exitm} |
| 3120 | * Extern:: @code{.extern} |
| 3121 | * Fail:: @code{.fail} |
| 3122 | @ifclear no-file-dir |
| 3123 | * File:: @code{.file @var{string}} |
| 3124 | @end ifclear |
| 3125 | |
| 3126 | * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}} |
| 3127 | * Float:: @code{.float @var{flonums}} |
| 3128 | * Func:: @code{.func} |
| 3129 | * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}} |
| 3130 | * hword:: @code{.hword @var{expressions}} |
| 3131 | * Ident:: @code{.ident} |
| 3132 | * If:: @code{.if @var{absolute expression}} |
| 3133 | * Include:: @code{.include "@var{file}"} |
| 3134 | * Int:: @code{.int @var{expressions}} |
| 3135 | * Irp:: @code{.irp @var{symbol},@var{values}}@dots{} |
| 3136 | * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{} |
| 3137 | * Lcomm:: @code{.lcomm @var{symbol} , @var{length}} |
| 3138 | * Lflags:: @code{.lflags} |
| 3139 | @ifclear no-line-dir |
| 3140 | * Line:: @code{.line @var{line-number}} |
| 3141 | @end ifclear |
| 3142 | |
| 3143 | * Ln:: @code{.ln @var{line-number}} |
| 3144 | * Linkonce:: @code{.linkonce [@var{type}]} |
| 3145 | * List:: @code{.list} |
| 3146 | * Long:: @code{.long @var{expressions}} |
| 3147 | @ignore |
| 3148 | * Lsym:: @code{.lsym @var{symbol}, @var{expression}} |
| 3149 | @end ignore |
| 3150 | |
| 3151 | * Macro:: @code{.macro @var{name} @var{args}}@dots{} |
| 3152 | * MRI:: @code{.mri @var{val}} |
| 3153 | |
| 3154 | * Nolist:: @code{.nolist} |
| 3155 | * Octa:: @code{.octa @var{bignums}} |
| 3156 | * Org:: @code{.org @var{new-lc} , @var{fill}} |
| 3157 | * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}} |
| 3158 | * Print:: @code{.print @var{string}} |
| 3159 | * Psize:: @code{.psize @var{lines}, @var{columns}} |
| 3160 | * Purgem:: @code{.purgem @var{name}} |
| 3161 | * Quad:: @code{.quad @var{bignums}} |
| 3162 | * Rept:: @code{.rept @var{count}} |
| 3163 | * Sbttl:: @code{.sbttl "@var{subheading}"} |
| 3164 | @ifset COFF |
| 3165 | * Scl:: @code{.scl @var{class}} |
| 3166 | * Section:: @code{.section @var{name}, @var{subsection}} |
| 3167 | @end ifset |
| 3168 | |
| 3169 | * Set:: @code{.set @var{symbol}, @var{expression}} |
| 3170 | * Short:: @code{.short @var{expressions}} |
| 3171 | * Single:: @code{.single @var{flonums}} |
| 3172 | @ifset COFF |
| 3173 | * Size:: @code{.size} |
| 3174 | @end ifset |
| 3175 | |
| 3176 | * Skip:: @code{.skip @var{size} , @var{fill}} |
| 3177 | * Sleb128:: @code{.sleb128 @var{expressions}} |
| 3178 | * Space:: @code{.space @var{size} , @var{fill}} |
| 3179 | @ifset have-stabs |
| 3180 | * Stab:: @code{.stabd, .stabn, .stabs} |
| 3181 | @end ifset |
| 3182 | |
| 3183 | * String:: @code{.string "@var{str}"} |
| 3184 | * Struct:: @code{.struct @var{expression}} |
| 3185 | @ifset ELF |
| 3186 | * Symver:: @code{.symver @var{name},@var{name2@@nodename}} |
| 3187 | @end ifset |
| 3188 | @ifset COFF |
| 3189 | * Tag:: @code{.tag @var{structname}} |
| 3190 | @end ifset |
| 3191 | |
| 3192 | * Text:: @code{.text @var{subsection}} |
| 3193 | * Title:: @code{.title "@var{heading}"} |
| 3194 | @ifset COFF |
| 3195 | * Type:: @code{.type @var{int}} |
| 3196 | * Val:: @code{.val @var{addr}} |
| 3197 | @end ifset |
| 3198 | @ifset ELF |
| 3199 | * Visibility:: @code{.internal @var{name}, .hidden @var{name}, .protected @var{name}} |
| 3200 | @end ifset |
| 3201 | |
| 3202 | * Uleb128:: @code{.uleb128 @var{expressions}} |
| 3203 | * Word:: @code{.word @var{expressions}} |
| 3204 | * Deprecated:: Deprecated Directives |
| 3205 | @end menu |
| 3206 | |
| 3207 | @node Abort |
| 3208 | @section @code{.abort} |
| 3209 | |
| 3210 | @cindex @code{abort} directive |
| 3211 | @cindex stopping the assembly |
| 3212 | This directive stops the assembly immediately. It is for |
| 3213 | compatibility with other assemblers. The original idea was that the |
| 3214 | assembly language source would be piped into the assembler. If the sender |
| 3215 | of the source quit, it could use this directive tells @code{@value{AS}} to |
| 3216 | quit also. One day @code{.abort} will not be supported. |
| 3217 | |
| 3218 | @ifset COFF |
| 3219 | @node ABORT |
| 3220 | @section @code{.ABORT} |
| 3221 | |
| 3222 | @cindex @code{ABORT} directive |
| 3223 | When producing COFF output, @code{@value{AS}} accepts this directive as a |
| 3224 | synonym for @samp{.abort}. |
| 3225 | |
| 3226 | @ifset BOUT |
| 3227 | When producing @code{b.out} output, @code{@value{AS}} accepts this directive, |
| 3228 | but ignores it. |
| 3229 | @end ifset |
| 3230 | @end ifset |
| 3231 | |
| 3232 | @node Align |
| 3233 | @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}} |
| 3234 | |
| 3235 | @cindex padding the location counter |
| 3236 | @cindex @code{align} directive |
| 3237 | Pad the location counter (in the current subsection) to a particular storage |
| 3238 | boundary. The first expression (which must be absolute) is the alignment |
| 3239 | required, as described below. |
| 3240 | |
| 3241 | The second expression (also absolute) gives the fill value to be stored in the |
| 3242 | padding bytes. It (and the comma) may be omitted. If it is omitted, the |
| 3243 | padding bytes are normally zero. However, on some systems, if the section is |
| 3244 | marked as containing code and the fill value is omitted, the space is filled |
| 3245 | with no-op instructions. |
| 3246 | |
| 3247 | The third expression is also absolute, and is also optional. If it is present, |
| 3248 | it is the maximum number of bytes that should be skipped by this alignment |
| 3249 | directive. If doing the alignment would require skipping more bytes than the |
| 3250 | specified maximum, then the alignment is not done at all. You can omit the |
| 3251 | fill value (the second argument) entirely by simply using two commas after the |
| 3252 | required alignment; this can be useful if you want the alignment to be filled |
| 3253 | with no-op instructions when appropriate. |
| 3254 | |
| 3255 | The way the required alignment is specified varies from system to system. |
| 3256 | For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF |
| 3257 | format, |
| 3258 | the first expression is the |
| 3259 | alignment request in bytes. For example @samp{.align 8} advances |
| 3260 | the location counter until it is a multiple of 8. If the location counter |
| 3261 | is already a multiple of 8, no change is needed. |
| 3262 | |
| 3263 | For other systems, including the i386 using a.out format, it is the |
| 3264 | number of low-order zero bits the location counter must have after |
| 3265 | advancement. For example @samp{.align 3} advances the location |
| 3266 | counter until it a multiple of 8. If the location counter is already a |
| 3267 | multiple of 8, no change is needed. |
| 3268 | |
| 3269 | This inconsistency is due to the different behaviors of the various |
| 3270 | native assemblers for these systems which GAS must emulate. |
| 3271 | GAS also provides @code{.balign} and @code{.p2align} directives, |
| 3272 | described later, which have a consistent behavior across all |
| 3273 | architectures (but are specific to GAS). |
| 3274 | |
| 3275 | @node Ascii |
| 3276 | @section @code{.ascii "@var{string}"}@dots{} |
| 3277 | |
| 3278 | @cindex @code{ascii} directive |
| 3279 | @cindex string literals |
| 3280 | @code{.ascii} expects zero or more string literals (@pxref{Strings}) |
| 3281 | separated by commas. It assembles each string (with no automatic |
| 3282 | trailing zero byte) into consecutive addresses. |
| 3283 | |
| 3284 | @node Asciz |
| 3285 | @section @code{.asciz "@var{string}"}@dots{} |
| 3286 | |
| 3287 | @cindex @code{asciz} directive |
| 3288 | @cindex zero-terminated strings |
| 3289 | @cindex null-terminated strings |
| 3290 | @code{.asciz} is just like @code{.ascii}, but each string is followed by |
| 3291 | a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''. |
| 3292 | |
| 3293 | @node Balign |
| 3294 | @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}} |
| 3295 | |
| 3296 | @cindex padding the location counter given number of bytes |
| 3297 | @cindex @code{balign} directive |
| 3298 | Pad the location counter (in the current subsection) to a particular |
| 3299 | storage boundary. The first expression (which must be absolute) is the |
| 3300 | alignment request in bytes. For example @samp{.balign 8} advances |
| 3301 | the location counter until it is a multiple of 8. If the location counter |
| 3302 | is already a multiple of 8, no change is needed. |
| 3303 | |
| 3304 | The second expression (also absolute) gives the fill value to be stored in the |
| 3305 | padding bytes. It (and the comma) may be omitted. If it is omitted, the |
| 3306 | padding bytes are normally zero. However, on some systems, if the section is |
| 3307 | marked as containing code and the fill value is omitted, the space is filled |
| 3308 | with no-op instructions. |
| 3309 | |
| 3310 | The third expression is also absolute, and is also optional. If it is present, |
| 3311 | it is the maximum number of bytes that should be skipped by this alignment |
| 3312 | directive. If doing the alignment would require skipping more bytes than the |
| 3313 | specified maximum, then the alignment is not done at all. You can omit the |
| 3314 | fill value (the second argument) entirely by simply using two commas after the |
| 3315 | required alignment; this can be useful if you want the alignment to be filled |
| 3316 | with no-op instructions when appropriate. |
| 3317 | |
| 3318 | @cindex @code{balignw} directive |
| 3319 | @cindex @code{balignl} directive |
| 3320 | The @code{.balignw} and @code{.balignl} directives are variants of the |
| 3321 | @code{.balign} directive. The @code{.balignw} directive treats the fill |
| 3322 | pattern as a two byte word value. The @code{.balignl} directives treats the |
| 3323 | fill pattern as a four byte longword value. For example, @code{.balignw |
| 3324 | 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be |
| 3325 | filled in with the value 0x368d (the exact placement of the bytes depends upon |
| 3326 | the endianness of the processor). If it skips 1 or 3 bytes, the fill value is |
| 3327 | undefined. |
| 3328 | |
| 3329 | @node Byte |
| 3330 | @section @code{.byte @var{expressions}} |
| 3331 | |
| 3332 | @cindex @code{byte} directive |
| 3333 | @cindex integers, one byte |
| 3334 | @code{.byte} expects zero or more expressions, separated by commas. |
| 3335 | Each expression is assembled into the next byte. |
| 3336 | |
| 3337 | @node Comm |
| 3338 | @section @code{.comm @var{symbol} , @var{length} } |
| 3339 | |
| 3340 | @cindex @code{comm} directive |
| 3341 | @cindex symbol, common |
| 3342 | @code{.comm} declares a common symbol named @var{symbol}. When linking, a |
| 3343 | common symbol in one object file may be merged with a defined or common symbol |
| 3344 | of the same name in another object file. If @code{@value{LD}} does not see a |
| 3345 | definition for the symbol--just one or more common symbols--then it will |
| 3346 | allocate @var{length} bytes of uninitialized memory. @var{length} must be an |
| 3347 | absolute expression. If @code{@value{LD}} sees multiple common symbols with |
| 3348 | the same name, and they do not all have the same size, it will allocate space |
| 3349 | using the largest size. |
| 3350 | |
| 3351 | @ifset ELF |
| 3352 | When using ELF, the @code{.comm} directive takes an optional third argument. |
| 3353 | This is the desired alignment of the symbol, specified as a byte boundary (for |
| 3354 | example, an alignment of 16 means that the least significant 4 bits of the |
| 3355 | address should be zero). The alignment must be an absolute expression, and it |
| 3356 | must be a power of two. If @code{@value{LD}} allocates uninitialized memory |
| 3357 | for the common symbol, it will use the alignment when placing the symbol. If |
| 3358 | no alignment is specified, @code{@value{AS}} will set the alignment to the |
| 3359 | largest power of two less than or equal to the size of the symbol, up to a |
| 3360 | maximum of 16. |
| 3361 | @end ifset |
| 3362 | |
| 3363 | @ifset HPPA |
| 3364 | The syntax for @code{.comm} differs slightly on the HPPA. The syntax is |
| 3365 | @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional. |
| 3366 | @end ifset |
| 3367 | |
| 3368 | @node Data |
| 3369 | @section @code{.data @var{subsection}} |
| 3370 | |
| 3371 | @cindex @code{data} directive |
| 3372 | @code{.data} tells @code{@value{AS}} to assemble the following statements onto the |
| 3373 | end of the data subsection numbered @var{subsection} (which is an |
| 3374 | absolute expression). If @var{subsection} is omitted, it defaults |
| 3375 | to zero. |
| 3376 | |
| 3377 | @ifset COFF |
| 3378 | @node Def |
| 3379 | @section @code{.def @var{name}} |
| 3380 | |
| 3381 | @cindex @code{def} directive |
| 3382 | @cindex COFF symbols, debugging |
| 3383 | @cindex debugging COFF symbols |
| 3384 | Begin defining debugging information for a symbol @var{name}; the |
| 3385 | definition extends until the @code{.endef} directive is encountered. |
| 3386 | @ifset BOUT |
| 3387 | |
| 3388 | This directive is only observed when @code{@value{AS}} is configured for COFF |
| 3389 | format output; when producing @code{b.out}, @samp{.def} is recognized, |
| 3390 | but ignored. |
| 3391 | @end ifset |
| 3392 | @end ifset |
| 3393 | |
| 3394 | @ifset aout-bout |
| 3395 | @node Desc |
| 3396 | @section @code{.desc @var{symbol}, @var{abs-expression}} |
| 3397 | |
| 3398 | @cindex @code{desc} directive |
| 3399 | @cindex COFF symbol descriptor |
| 3400 | @cindex symbol descriptor, COFF |
| 3401 | This directive sets the descriptor of the symbol (@pxref{Symbol Attributes}) |
| 3402 | to the low 16 bits of an absolute expression. |
| 3403 | |
| 3404 | @ifset COFF |
| 3405 | The @samp{.desc} directive is not available when @code{@value{AS}} is |
| 3406 | configured for COFF output; it is only for @code{a.out} or @code{b.out} |
| 3407 | object format. For the sake of compatibility, @code{@value{AS}} accepts |
| 3408 | it, but produces no output, when configured for COFF. |
| 3409 | @end ifset |
| 3410 | @end ifset |
| 3411 | |
| 3412 | @ifset COFF |
| 3413 | @node Dim |
| 3414 | @section @code{.dim} |
| 3415 | |
| 3416 | @cindex @code{dim} directive |
| 3417 | @cindex COFF auxiliary symbol information |
| 3418 | @cindex auxiliary symbol information, COFF |
| 3419 | This directive is generated by compilers to include auxiliary debugging |
| 3420 | information in the symbol table. It is only permitted inside |
| 3421 | @code{.def}/@code{.endef} pairs. |
| 3422 | @ifset BOUT |
| 3423 | |
| 3424 | @samp{.dim} is only meaningful when generating COFF format output; when |
| 3425 | @code{@value{AS}} is generating @code{b.out}, it accepts this directive but |
| 3426 | ignores it. |
| 3427 | @end ifset |
| 3428 | @end ifset |
| 3429 | |
| 3430 | @node Double |
| 3431 | @section @code{.double @var{flonums}} |
| 3432 | |
| 3433 | @cindex @code{double} directive |
| 3434 | @cindex floating point numbers (double) |
| 3435 | @code{.double} expects zero or more flonums, separated by commas. It |
| 3436 | assembles floating point numbers. |
| 3437 | @ifset GENERIC |
| 3438 | The exact kind of floating point numbers emitted depends on how |
| 3439 | @code{@value{AS}} is configured. @xref{Machine Dependencies}. |
| 3440 | @end ifset |
| 3441 | @ifclear GENERIC |
| 3442 | @ifset IEEEFLOAT |
| 3443 | On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers |
| 3444 | in @sc{ieee} format. |
| 3445 | @end ifset |
| 3446 | @end ifclear |
| 3447 | |
| 3448 | @node Eject |
| 3449 | @section @code{.eject} |
| 3450 | |
| 3451 | @cindex @code{eject} directive |
| 3452 | @cindex new page, in listings |
| 3453 | @cindex page, in listings |
| 3454 | @cindex listing control: new page |
| 3455 | Force a page break at this point, when generating assembly listings. |
| 3456 | |
| 3457 | @node Else |
| 3458 | @section @code{.else} |
| 3459 | |
| 3460 | @cindex @code{else} directive |
| 3461 | @code{.else} is part of the @code{@value{AS}} support for conditional |
| 3462 | assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section |
| 3463 | of code to be assembled if the condition for the preceding @code{.if} |
| 3464 | was false. |
| 3465 | |
| 3466 | @node End |
| 3467 | @section @code{.end} |
| 3468 | |
| 3469 | @cindex @code{end} directive |
| 3470 | @code{.end} marks the end of the assembly file. @code{@value{AS}} does not |
| 3471 | process anything in the file past the @code{.end} directive. |
| 3472 | |
| 3473 | @ifset COFF |
| 3474 | @node Endef |
| 3475 | @section @code{.endef} |
| 3476 | |
| 3477 | @cindex @code{endef} directive |
| 3478 | This directive flags the end of a symbol definition begun with |
| 3479 | @code{.def}. |
| 3480 | @ifset BOUT |
| 3481 | |
| 3482 | @samp{.endef} is only meaningful when generating COFF format output; if |
| 3483 | @code{@value{AS}} is configured to generate @code{b.out}, it accepts this |
| 3484 | directive but ignores it. |
| 3485 | @end ifset |
| 3486 | @end ifset |
| 3487 | |
| 3488 | @node Endfunc |
| 3489 | @section @code{.endfunc} |
| 3490 | @cindex @code{endfunc} directive |
| 3491 | @code{.endfunc} marks the end of a function specified with @code{.func}. |
| 3492 | |
| 3493 | @node Endif |
| 3494 | @section @code{.endif} |
| 3495 | |
| 3496 | @cindex @code{endif} directive |
| 3497 | @code{.endif} is part of the @code{@value{AS}} support for conditional assembly; |
| 3498 | it marks the end of a block of code that is only assembled |
| 3499 | conditionally. @xref{If,,@code{.if}}. |
| 3500 | |
| 3501 | @node Equ |
| 3502 | @section @code{.equ @var{symbol}, @var{expression}} |
| 3503 | |
| 3504 | @cindex @code{equ} directive |
| 3505 | @cindex assigning values to symbols |
| 3506 | @cindex symbols, assigning values to |
| 3507 | This directive sets the value of @var{symbol} to @var{expression}. |
| 3508 | It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}. |
| 3509 | |
| 3510 | @ifset HPPA |
| 3511 | The syntax for @code{equ} on the HPPA is |
| 3512 | @samp{@var{symbol} .equ @var{expression}}. |
| 3513 | @end ifset |
| 3514 | |
| 3515 | @node Equiv |
| 3516 | @section @code{.equiv @var{symbol}, @var{expression}} |
| 3517 | @cindex @code{equiv} directive |
| 3518 | The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that |
| 3519 | the assembler will signal an error if @var{symbol} is already defined. |
| 3520 | |
| 3521 | Except for the contents of the error message, this is roughly equivalent to |
| 3522 | @smallexample |
| 3523 | .ifdef SYM |
| 3524 | .err |
| 3525 | .endif |
| 3526 | .equ SYM,VAL |
| 3527 | @end smallexample |
| 3528 | |
| 3529 | @node Err |
| 3530 | @section @code{.err} |
| 3531 | @cindex @code{err} directive |
| 3532 | If @code{@value{AS}} assembles a @code{.err} directive, it will print an error |
| 3533 | message and, unless the @code{-Z} option was used, it will not generate an |
| 3534 | object file. This can be used to signal error an conditionally compiled code. |
| 3535 | |
| 3536 | @node Exitm |
| 3537 | @section @code{.exitm} |
| 3538 | Exit early from the current macro definition. @xref{Macro}. |
| 3539 | |
| 3540 | @node Extern |
| 3541 | @section @code{.extern} |
| 3542 | |
| 3543 | @cindex @code{extern} directive |
| 3544 | @code{.extern} is accepted in the source program---for compatibility |
| 3545 | with other assemblers---but it is ignored. @code{@value{AS}} treats |
| 3546 | all undefined symbols as external. |
| 3547 | |
| 3548 | @node Fail |
| 3549 | @section @code{.fail @var{expression}} |
| 3550 | |
| 3551 | @cindex @code{fail} directive |
| 3552 | Generates an error or a warning. If the value of the @var{expression} is 500 |
| 3553 | or more, @code{@value{AS}} will print a warning message. If the value is less |
| 3554 | than 500, @code{@value{AS}} will print an error message. The message will |
| 3555 | include the value of @var{expression}. This can occasionally be useful inside |
| 3556 | complex nested macros or conditional assembly. |
| 3557 | |
| 3558 | @ifclear no-file-dir |
| 3559 | @node File |
| 3560 | @section @code{.file @var{string}} |
| 3561 | |
| 3562 | @cindex @code{file} directive |
| 3563 | @cindex logical file name |
| 3564 | @cindex file name, logical |
| 3565 | @code{.file} tells @code{@value{AS}} that we are about to start a new logical |
| 3566 | file. @var{string} is the new file name. In general, the filename is |
| 3567 | recognized whether or not it is surrounded by quotes @samp{"}; but if you wish |
| 3568 | to specify an empty file name, you must give the quotes--@code{""}. This |
| 3569 | statement may go away in future: it is only recognized to be compatible with |
| 3570 | old @code{@value{AS}} programs. |
| 3571 | @ifset A29K |
| 3572 | In some configurations of @code{@value{AS}}, @code{.file} has already been |
| 3573 | removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}. |
| 3574 | @end ifset |
| 3575 | @end ifclear |
| 3576 | |
| 3577 | @node Fill |
| 3578 | @section @code{.fill @var{repeat} , @var{size} , @var{value}} |
| 3579 | |
| 3580 | @cindex @code{fill} directive |
| 3581 | @cindex writing patterns in memory |
| 3582 | @cindex patterns, writing in memory |
| 3583 | @var{result}, @var{size} and @var{value} are absolute expressions. |
| 3584 | This emits @var{repeat} copies of @var{size} bytes. @var{Repeat} |
| 3585 | may be zero or more. @var{Size} may be zero or more, but if it is |
| 3586 | more than 8, then it is deemed to have the value 8, compatible with |
| 3587 | other people's assemblers. The contents of each @var{repeat} bytes |
| 3588 | is taken from an 8-byte number. The highest order 4 bytes are |
| 3589 | zero. The lowest order 4 bytes are @var{value} rendered in the |
| 3590 | byte-order of an integer on the computer @code{@value{AS}} is assembling for. |
| 3591 | Each @var{size} bytes in a repetition is taken from the lowest order |
| 3592 | @var{size} bytes of this number. Again, this bizarre behavior is |
| 3593 | compatible with other people's assemblers. |
| 3594 | |
| 3595 | @var{size} and @var{value} are optional. |
| 3596 | If the second comma and @var{value} are absent, @var{value} is |
| 3597 | assumed zero. If the first comma and following tokens are absent, |
| 3598 | @var{size} is assumed to be 1. |
| 3599 | |
| 3600 | @node Float |
| 3601 | @section @code{.float @var{flonums}} |
| 3602 | |
| 3603 | @cindex floating point numbers (single) |
| 3604 | @cindex @code{float} directive |
| 3605 | This directive assembles zero or more flonums, separated by commas. It |
| 3606 | has the same effect as @code{.single}. |
| 3607 | @ifset GENERIC |
| 3608 | The exact kind of floating point numbers emitted depends on how |
| 3609 | @code{@value{AS}} is configured. |
| 3610 | @xref{Machine Dependencies}. |
| 3611 | @end ifset |
| 3612 | @ifclear GENERIC |
| 3613 | @ifset IEEEFLOAT |
| 3614 | On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers |
| 3615 | in @sc{ieee} format. |
| 3616 | @end ifset |
| 3617 | @end ifclear |
| 3618 | |
| 3619 | @node Func |
| 3620 | @section @code{.func @var{name}[,@var{label}]} |
| 3621 | @cindex @code{func} directive |
| 3622 | @code{.func} emits debugging information to denote function @var{name}, and |
| 3623 | is ignored unless the file is assembled with debugging enabled. |
| 3624 | Only @samp{--gstabs} is currently supported. |
| 3625 | @var{label} is the entry point of the function and if omitted @var{name} |
| 3626 | prepended with the @samp{leading char} is used. |
| 3627 | @samp{leading char} is usually @code{_} or nothing, depending on the target. |
| 3628 | All functions are currently defined to have @code{void} return type. |
| 3629 | The function must be terminated with @code{.endfunc}. |
| 3630 | |
| 3631 | @node Global |
| 3632 | @section @code{.global @var{symbol}}, @code{.globl @var{symbol}} |
| 3633 | |
| 3634 | @cindex @code{global} directive |
| 3635 | @cindex symbol, making visible to linker |
| 3636 | @code{.global} makes the symbol visible to @code{@value{LD}}. If you define |
| 3637 | @var{symbol} in your partial program, its value is made available to |
| 3638 | other partial programs that are linked with it. Otherwise, |
| 3639 | @var{symbol} takes its attributes from a symbol of the same name |
| 3640 | from another file linked into the same program. |
| 3641 | |
| 3642 | Both spellings (@samp{.globl} and @samp{.global}) are accepted, for |
| 3643 | compatibility with other assemblers. |
| 3644 | |
| 3645 | @ifset HPPA |
| 3646 | On the HPPA, @code{.global} is not always enough to make it accessible to other |
| 3647 | partial programs. You may need the HPPA-only @code{.EXPORT} directive as well. |
| 3648 | @xref{HPPA Directives,, HPPA Assembler Directives}. |
| 3649 | @end ifset |
| 3650 | |
| 3651 | @node hword |
| 3652 | @section @code{.hword @var{expressions}} |
| 3653 | |
| 3654 | @cindex @code{hword} directive |
| 3655 | @cindex integers, 16-bit |
| 3656 | @cindex numbers, 16-bit |
| 3657 | @cindex sixteen bit integers |
| 3658 | This expects zero or more @var{expressions}, and emits |
| 3659 | a 16 bit number for each. |
| 3660 | |
| 3661 | @ifset GENERIC |
| 3662 | This directive is a synonym for @samp{.short}; depending on the target |
| 3663 | architecture, it may also be a synonym for @samp{.word}. |
| 3664 | @end ifset |
| 3665 | @ifclear GENERIC |
| 3666 | @ifset W32 |
| 3667 | This directive is a synonym for @samp{.short}. |
| 3668 | @end ifset |
| 3669 | @ifset W16 |
| 3670 | This directive is a synonym for both @samp{.short} and @samp{.word}. |
| 3671 | @end ifset |
| 3672 | @end ifclear |
| 3673 | |
| 3674 | @node Ident |
| 3675 | @section @code{.ident} |
| 3676 | |
| 3677 | @cindex @code{ident} directive |
| 3678 | This directive is used by some assemblers to place tags in object files. |
| 3679 | @code{@value{AS}} simply accepts the directive for source-file |
| 3680 | compatibility with such assemblers, but does not actually emit anything |
| 3681 | for it. |
| 3682 | |
| 3683 | @node If |
| 3684 | @section @code{.if @var{absolute expression}} |
| 3685 | |
| 3686 | @cindex conditional assembly |
| 3687 | @cindex @code{if} directive |
| 3688 | @code{.if} marks the beginning of a section of code which is only |
| 3689 | considered part of the source program being assembled if the argument |
| 3690 | (which must be an @var{absolute expression}) is non-zero. The end of |
| 3691 | the conditional section of code must be marked by @code{.endif} |
| 3692 | (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the |
| 3693 | alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}). |
| 3694 | |
| 3695 | The following variants of @code{.if} are also supported: |
| 3696 | @table @code |
| 3697 | @cindex @code{ifdef} directive |
| 3698 | @item .ifdef @var{symbol} |
| 3699 | Assembles the following section of code if the specified @var{symbol} |
| 3700 | has been defined. |
| 3701 | |
| 3702 | @cindex @code{ifc} directive |
| 3703 | @item .ifc @var{string1},@var{string2} |
| 3704 | Assembles the following section of code if the two strings are the same. The |
| 3705 | strings may be optionally quoted with single quotes. If they are not quoted, |
| 3706 | the first string stops at the first comma, and the second string stops at the |
| 3707 | end of the line. Strings which contain whitespace should be quoted. The |
| 3708 | string comparison is case sensitive. |
| 3709 | |
| 3710 | @cindex @code{ifeq} directive |
| 3711 | @item .ifeq @var{absolute expression} |
| 3712 | Assembles the following section of code if the argument is zero. |
| 3713 | |
| 3714 | @cindex @code{ifeqs} directive |
| 3715 | @item .ifeqs @var{string1},@var{string2} |
| 3716 | Another form of @code{.ifc}. The strings must be quoted using double quotes. |
| 3717 | |
| 3718 | @cindex @code{ifge} directive |
| 3719 | @item .ifge @var{absolute expression} |
| 3720 | Assembles the following section of code if the argument is greater than or |
| 3721 | equal to zero. |
| 3722 | |
| 3723 | @cindex @code{ifgt} directive |
| 3724 | @item .ifgt @var{absolute expression} |
| 3725 | Assembles the following section of code if the argument is greater than zero. |
| 3726 | |
| 3727 | @cindex @code{ifle} directive |
| 3728 | @item .ifle @var{absolute expression} |
| 3729 | Assembles the following section of code if the argument is less than or equal |
| 3730 | to zero. |
| 3731 | |
| 3732 | @cindex @code{iflt} directive |
| 3733 | @item .iflt @var{absolute expression} |
| 3734 | Assembles the following section of code if the argument is less than zero. |
| 3735 | |
| 3736 | @cindex @code{ifnc} directive |
| 3737 | @item .ifnc @var{string1},@var{string2}. |
| 3738 | Like @code{.ifc}, but the sense of the test is reversed: this assembles the |
| 3739 | following section of code if the two strings are not the same. |
| 3740 | |
| 3741 | @cindex @code{ifndef} directive |
| 3742 | @cindex @code{ifnotdef} directive |
| 3743 | @item .ifndef @var{symbol} |
| 3744 | @itemx .ifnotdef @var{symbol} |
| 3745 | Assembles the following section of code if the specified @var{symbol} |
| 3746 | has not been defined. Both spelling variants are equivalent. |
| 3747 | |
| 3748 | @cindex @code{ifne} directive |
| 3749 | @item .ifne @var{absolute expression} |
| 3750 | Assembles the following section of code if the argument is not equal to zero |
| 3751 | (in other words, this is equivalent to @code{.if}). |
| 3752 | |
| 3753 | @cindex @code{ifnes} directive |
| 3754 | @item .ifnes @var{string1},@var{string2} |
| 3755 | Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the |
| 3756 | following section of code if the two strings are not the same. |
| 3757 | @end table |
| 3758 | |
| 3759 | @node Include |
| 3760 | @section @code{.include "@var{file}"} |
| 3761 | |
| 3762 | @cindex @code{include} directive |
| 3763 | @cindex supporting files, including |
| 3764 | @cindex files, including |
| 3765 | This directive provides a way to include supporting files at specified |
| 3766 | points in your source program. The code from @var{file} is assembled as |
| 3767 | if it followed the point of the @code{.include}; when the end of the |
| 3768 | included file is reached, assembly of the original file continues. You |
| 3769 | can control the search paths used with the @samp{-I} command-line option |
| 3770 | (@pxref{Invoking,,Command-Line Options}). Quotation marks are required |
| 3771 | around @var{file}. |
| 3772 | |
| 3773 | @node Int |
| 3774 | @section @code{.int @var{expressions}} |
| 3775 | |
| 3776 | @cindex @code{int} directive |
| 3777 | @cindex integers, 32-bit |
| 3778 | Expect zero or more @var{expressions}, of any section, separated by commas. |
| 3779 | For each expression, emit a number that, at run time, is the value of that |
| 3780 | expression. The byte order and bit size of the number depends on what kind |
| 3781 | of target the assembly is for. |
| 3782 | |
| 3783 | @ifclear GENERIC |
| 3784 | @ifset H8 |
| 3785 | On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit |
| 3786 | integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits |
| 3787 | 32-bit integers. |
| 3788 | @end ifset |
| 3789 | @end ifclear |
| 3790 | |
| 3791 | @node Irp |
| 3792 | @section @code{.irp @var{symbol},@var{values}}@dots{} |
| 3793 | |
| 3794 | @cindex @code{irp} directive |
| 3795 | Evaluate a sequence of statements assigning different values to @var{symbol}. |
| 3796 | The sequence of statements starts at the @code{.irp} directive, and is |
| 3797 | terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is |
| 3798 | set to @var{value}, and the sequence of statements is assembled. If no |
| 3799 | @var{value} is listed, the sequence of statements is assembled once, with |
| 3800 | @var{symbol} set to the null string. To refer to @var{symbol} within the |
| 3801 | sequence of statements, use @var{\symbol}. |
| 3802 | |
| 3803 | For example, assembling |
| 3804 | |
| 3805 | @example |
| 3806 | .irp param,1,2,3 |
| 3807 | move d\param,sp@@- |
| 3808 | .endr |
| 3809 | @end example |
| 3810 | |
| 3811 | is equivalent to assembling |
| 3812 | |
| 3813 | @example |
| 3814 | move d1,sp@@- |
| 3815 | move d2,sp@@- |
| 3816 | move d3,sp@@- |
| 3817 | @end example |
| 3818 | |
| 3819 | @node Irpc |
| 3820 | @section @code{.irpc @var{symbol},@var{values}}@dots{} |
| 3821 | |
| 3822 | @cindex @code{irpc} directive |
| 3823 | Evaluate a sequence of statements assigning different values to @var{symbol}. |
| 3824 | The sequence of statements starts at the @code{.irpc} directive, and is |
| 3825 | terminated by an @code{.endr} directive. For each character in @var{value}, |
| 3826 | @var{symbol} is set to the character, and the sequence of statements is |
| 3827 | assembled. If no @var{value} is listed, the sequence of statements is |
| 3828 | assembled once, with @var{symbol} set to the null string. To refer to |
| 3829 | @var{symbol} within the sequence of statements, use @var{\symbol}. |
| 3830 | |
| 3831 | For example, assembling |
| 3832 | |
| 3833 | @example |
| 3834 | .irpc param,123 |
| 3835 | move d\param,sp@@- |
| 3836 | .endr |
| 3837 | @end example |
| 3838 | |
| 3839 | is equivalent to assembling |
| 3840 | |
| 3841 | @example |
| 3842 | move d1,sp@@- |
| 3843 | move d2,sp@@- |
| 3844 | move d3,sp@@- |
| 3845 | @end example |
| 3846 | |
| 3847 | @node Lcomm |
| 3848 | @section @code{.lcomm @var{symbol} , @var{length}} |
| 3849 | |
| 3850 | @cindex @code{lcomm} directive |
| 3851 | @cindex local common symbols |
| 3852 | @cindex symbols, local common |
| 3853 | Reserve @var{length} (an absolute expression) bytes for a local common |
| 3854 | denoted by @var{symbol}. The section and value of @var{symbol} are |
| 3855 | those of the new local common. The addresses are allocated in the bss |
| 3856 | section, so that at run-time the bytes start off zeroed. @var{Symbol} |
| 3857 | is not declared global (@pxref{Global,,@code{.global}}), so is normally |
| 3858 | not visible to @code{@value{LD}}. |
| 3859 | |
| 3860 | @ifset GENERIC |
| 3861 | Some targets permit a third argument to be used with @code{.lcomm}. This |
| 3862 | argument specifies the desired alignment of the symbol in the bss section. |
| 3863 | @end ifset |
| 3864 | |
| 3865 | @ifset HPPA |
| 3866 | The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is |
| 3867 | @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional. |
| 3868 | @end ifset |
| 3869 | |
| 3870 | @node Lflags |
| 3871 | @section @code{.lflags} |
| 3872 | |
| 3873 | @cindex @code{lflags} directive (ignored) |
| 3874 | @code{@value{AS}} accepts this directive, for compatibility with other |
| 3875 | assemblers, but ignores it. |
| 3876 | |
| 3877 | @ifclear no-line-dir |
| 3878 | @node Line |
| 3879 | @section @code{.line @var{line-number}} |
| 3880 | |
| 3881 | @cindex @code{line} directive |
| 3882 | @end ifclear |
| 3883 | @ifset no-line-dir |
| 3884 | @node Ln |
| 3885 | @section @code{.ln @var{line-number}} |
| 3886 | |
| 3887 | @cindex @code{ln} directive |
| 3888 | @end ifset |
| 3889 | @cindex logical line number |
| 3890 | @ifset aout-bout |
| 3891 | Change the logical line number. @var{line-number} must be an absolute |
| 3892 | expression. The next line has that logical line number. Therefore any other |
| 3893 | statements on the current line (after a statement separator character) are |
| 3894 | reported as on logical line number @var{line-number} @minus{} 1. One day |
| 3895 | @code{@value{AS}} will no longer support this directive: it is recognized only |
| 3896 | for compatibility with existing assembler programs. |
| 3897 | |
| 3898 | @ifset GENERIC |
| 3899 | @ifset A29K |
| 3900 | @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is |
| 3901 | not available; use the synonym @code{.ln} in that context. |
| 3902 | @end ifset |
| 3903 | @end ifset |
| 3904 | @end ifset |
| 3905 | |
| 3906 | @ifclear no-line-dir |
| 3907 | Even though this is a directive associated with the @code{a.out} or |
| 3908 | @code{b.out} object-code formats, @code{@value{AS}} still recognizes it |
| 3909 | when producing COFF output, and treats @samp{.line} as though it |
| 3910 | were the COFF @samp{.ln} @emph{if} it is found outside a |
| 3911 | @code{.def}/@code{.endef} pair. |
| 3912 | |
| 3913 | Inside a @code{.def}, @samp{.line} is, instead, one of the directives |
| 3914 | used by compilers to generate auxiliary symbol information for |
| 3915 | debugging. |
| 3916 | @end ifclear |
| 3917 | |
| 3918 | @node Linkonce |
| 3919 | @section @code{.linkonce [@var{type}]} |
| 3920 | @cindex COMDAT |
| 3921 | @cindex @code{linkonce} directive |
| 3922 | @cindex common sections |
| 3923 | Mark the current section so that the linker only includes a single copy of it. |
| 3924 | This may be used to include the same section in several different object files, |
| 3925 | but ensure that the linker will only include it once in the final output file. |
| 3926 | The @code{.linkonce} pseudo-op must be used for each instance of the section. |
| 3927 | Duplicate sections are detected based on the section name, so it should be |
| 3928 | unique. |
| 3929 | |
| 3930 | This directive is only supported by a few object file formats; as of this |
| 3931 | writing, the only object file format which supports it is the Portable |
| 3932 | Executable format used on Windows NT. |
| 3933 | |
| 3934 | The @var{type} argument is optional. If specified, it must be one of the |
| 3935 | following strings. For example: |
| 3936 | @smallexample |
| 3937 | .linkonce same_size |
| 3938 | @end smallexample |
| 3939 | Not all types may be supported on all object file formats. |
| 3940 | |
| 3941 | @table @code |
| 3942 | @item discard |
| 3943 | Silently discard duplicate sections. This is the default. |
| 3944 | |
| 3945 | @item one_only |
| 3946 | Warn if there are duplicate sections, but still keep only one copy. |
| 3947 | |
| 3948 | @item same_size |
| 3949 | Warn if any of the duplicates have different sizes. |
| 3950 | |
| 3951 | @item same_contents |
| 3952 | Warn if any of the duplicates do not have exactly the same contents. |
| 3953 | @end table |
| 3954 | |
| 3955 | @node Ln |
| 3956 | @section @code{.ln @var{line-number}} |
| 3957 | |
| 3958 | @cindex @code{ln} directive |
| 3959 | @ifclear no-line-dir |
| 3960 | @samp{.ln} is a synonym for @samp{.line}. |
| 3961 | @end ifclear |
| 3962 | @ifset no-line-dir |
| 3963 | Tell @code{@value{AS}} to change the logical line number. @var{line-number} |
| 3964 | must be an absolute expression. The next line has that logical |
| 3965 | line number, so any other statements on the current line (after a |
| 3966 | statement separator character @code{;}) are reported as on logical |
| 3967 | line number @var{line-number} @minus{} 1. |
| 3968 | @ifset BOUT |
| 3969 | |
| 3970 | This directive is accepted, but ignored, when @code{@value{AS}} is |
| 3971 | configured for @code{b.out}; its effect is only associated with COFF |
| 3972 | output format. |
| 3973 | @end ifset |
| 3974 | @end ifset |
| 3975 | |
| 3976 | @node MRI |
| 3977 | @section @code{.mri @var{val}} |
| 3978 | |
| 3979 | @cindex @code{mri} directive |
| 3980 | @cindex MRI mode, temporarily |
| 3981 | If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If |
| 3982 | @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change |
| 3983 | affects code assembled until the next @code{.mri} directive, or until the end |
| 3984 | of the file. @xref{M, MRI mode, MRI mode}. |
| 3985 | |
| 3986 | @node List |
| 3987 | @section @code{.list} |
| 3988 | |
| 3989 | @cindex @code{list} directive |
| 3990 | @cindex listing control, turning on |
| 3991 | Control (in conjunction with the @code{.nolist} directive) whether or |
| 3992 | not assembly listings are generated. These two directives maintain an |
| 3993 | internal counter (which is zero initially). @code{.list} increments the |
| 3994 | counter, and @code{.nolist} decrements it. Assembly listings are |
| 3995 | generated whenever the counter is greater than zero. |
| 3996 | |
| 3997 | By default, listings are disabled. When you enable them (with the |
| 3998 | @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}), |
| 3999 | the initial value of the listing counter is one. |
| 4000 | |
| 4001 | @node Long |
| 4002 | @section @code{.long @var{expressions}} |
| 4003 | |
| 4004 | @cindex @code{long} directive |
| 4005 | @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}. |
| 4006 | |
| 4007 | @ignore |
| 4008 | @c no one seems to know what this is for or whether this description is |
| 4009 | @c what it really ought to do |
| 4010 | @node Lsym |
| 4011 | @section @code{.lsym @var{symbol}, @var{expression}} |
| 4012 | |
| 4013 | @cindex @code{lsym} directive |
| 4014 | @cindex symbol, not referenced in assembly |
| 4015 | @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in |
| 4016 | the hash table, ensuring it cannot be referenced by name during the |
| 4017 | rest of the assembly. This sets the attributes of the symbol to be |
| 4018 | the same as the expression value: |
| 4019 | @smallexample |
| 4020 | @var{other} = @var{descriptor} = 0 |
| 4021 | @var{type} = @r{(section of @var{expression})} |
| 4022 | @var{value} = @var{expression} |
| 4023 | @end smallexample |
| 4024 | @noindent |
| 4025 | The new symbol is not flagged as external. |
| 4026 | @end ignore |
| 4027 | |
| 4028 | @node Macro |
| 4029 | @section @code{.macro} |
| 4030 | |
| 4031 | @cindex macros |
| 4032 | The commands @code{.macro} and @code{.endm} allow you to define macros that |
| 4033 | generate assembly output. For example, this definition specifies a macro |
| 4034 | @code{sum} that puts a sequence of numbers into memory: |
| 4035 | |
| 4036 | @example |
| 4037 | .macro sum from=0, to=5 |
| 4038 | .long \from |
| 4039 | .if \to-\from |
| 4040 | sum "(\from+1)",\to |
| 4041 | .endif |
| 4042 | .endm |
| 4043 | @end example |
| 4044 | |
| 4045 | @noindent |
| 4046 | With that definition, @samp{SUM 0,5} is equivalent to this assembly input: |
| 4047 | |
| 4048 | @example |
| 4049 | .long 0 |
| 4050 | .long 1 |
| 4051 | .long 2 |
| 4052 | .long 3 |
| 4053 | .long 4 |
| 4054 | .long 5 |
| 4055 | @end example |
| 4056 | |
| 4057 | @ftable @code |
| 4058 | @item .macro @var{macname} |
| 4059 | @itemx .macro @var{macname} @var{macargs} @dots{} |
| 4060 | @cindex @code{macro} directive |
| 4061 | Begin the definition of a macro called @var{macname}. If your macro |
| 4062 | definition requires arguments, specify their names after the macro name, |
| 4063 | separated by commas or spaces. You can supply a default value for any |
| 4064 | macro argument by following the name with @samp{=@var{deflt}}. For |
| 4065 | example, these are all valid @code{.macro} statements: |
| 4066 | |
| 4067 | @table @code |
| 4068 | @item .macro comm |
| 4069 | Begin the definition of a macro called @code{comm}, which takes no |
| 4070 | arguments. |
| 4071 | |
| 4072 | @item .macro plus1 p, p1 |
| 4073 | @itemx .macro plus1 p p1 |
| 4074 | Either statement begins the definition of a macro called @code{plus1}, |
| 4075 | which takes two arguments; within the macro definition, write |
| 4076 | @samp{\p} or @samp{\p1} to evaluate the arguments. |
| 4077 | |
| 4078 | @item .macro reserve_str p1=0 p2 |
| 4079 | Begin the definition of a macro called @code{reserve_str}, with two |
| 4080 | arguments. The first argument has a default value, but not the second. |
| 4081 | After the definition is complete, you can call the macro either as |
| 4082 | @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to |
| 4083 | @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str |
| 4084 | ,@var{b}} (with @samp{\p1} evaluating as the default, in this case |
| 4085 | @samp{0}, and @samp{\p2} evaluating to @var{b}). |
| 4086 | @end table |
| 4087 | |
| 4088 | When you call a macro, you can specify the argument values either by |
| 4089 | position, or by keyword. For example, @samp{sum 9,17} is equivalent to |
| 4090 | @samp{sum to=17, from=9}. |
| 4091 | |
| 4092 | @item .endm |
| 4093 | @cindex @code{endm} directive |
| 4094 | Mark the end of a macro definition. |
| 4095 | |
| 4096 | @item .exitm |
| 4097 | @cindex @code{exitm} directive |
| 4098 | Exit early from the current macro definition. |
| 4099 | |
| 4100 | @cindex number of macros executed |
| 4101 | @cindex macros, count executed |
| 4102 | @item \@@ |
| 4103 | @code{@value{AS}} maintains a counter of how many macros it has |
| 4104 | executed in this pseudo-variable; you can copy that number to your |
| 4105 | output with @samp{\@@}, but @emph{only within a macro definition}. |
| 4106 | |
| 4107 | @ignore |
| 4108 | @item LOCAL @var{name} [ , @dots{} ] |
| 4109 | @emph{Warning: @code{LOCAL} is only available if you select ``alternate |
| 4110 | macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,, |
| 4111 | Alternate macro syntax}. |
| 4112 | |
| 4113 | Generate a string replacement for each of the @var{name} arguments, and |
| 4114 | replace any instances of @var{name} in each macro expansion. The |
| 4115 | replacement string is unique in the assembly, and different for each |
| 4116 | separate macro expansion. @code{LOCAL} allows you to write macros that |
| 4117 | define symbols, without fear of conflict between separate macro expansions. |
| 4118 | @end ignore |
| 4119 | @end ftable |
| 4120 | |
| 4121 | @node Nolist |
| 4122 | @section @code{.nolist} |
| 4123 | |
| 4124 | @cindex @code{nolist} directive |
| 4125 | @cindex listing control, turning off |
| 4126 | Control (in conjunction with the @code{.list} directive) whether or |
| 4127 | not assembly listings are generated. These two directives maintain an |
| 4128 | internal counter (which is zero initially). @code{.list} increments the |
| 4129 | counter, and @code{.nolist} decrements it. Assembly listings are |
| 4130 | generated whenever the counter is greater than zero. |
| 4131 | |
| 4132 | @node Octa |
| 4133 | @section @code{.octa @var{bignums}} |
| 4134 | |
| 4135 | @c FIXME: double size emitted for "octa" on i960, others? Or warn? |
| 4136 | @cindex @code{octa} directive |
| 4137 | @cindex integer, 16-byte |
| 4138 | @cindex sixteen byte integer |
| 4139 | This directive expects zero or more bignums, separated by commas. For each |
| 4140 | bignum, it emits a 16-byte integer. |
| 4141 | |
| 4142 | The term ``octa'' comes from contexts in which a ``word'' is two bytes; |
| 4143 | hence @emph{octa}-word for 16 bytes. |
| 4144 | |
| 4145 | @node Org |
| 4146 | @section @code{.org @var{new-lc} , @var{fill}} |
| 4147 | |
| 4148 | @cindex @code{org} directive |
| 4149 | @cindex location counter, advancing |
| 4150 | @cindex advancing location counter |
| 4151 | @cindex current address, advancing |
| 4152 | Advance the location counter of the current section to |
| 4153 | @var{new-lc}. @var{new-lc} is either an absolute expression or an |
| 4154 | expression with the same section as the current subsection. That is, |
| 4155 | you can't use @code{.org} to cross sections: if @var{new-lc} has the |
| 4156 | wrong section, the @code{.org} directive is ignored. To be compatible |
| 4157 | with former assemblers, if the section of @var{new-lc} is absolute, |
| 4158 | @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc} |
| 4159 | is the same as the current subsection. |
| 4160 | |
| 4161 | @code{.org} may only increase the location counter, or leave it |
| 4162 | unchanged; you cannot use @code{.org} to move the location counter |
| 4163 | backwards. |
| 4164 | |
| 4165 | @c double negative used below "not undefined" because this is a specific |
| 4166 | @c reference to "undefined" (as SEG_UNKNOWN is called in this manual) |
| 4167 | @c section. doc@cygnus.com 18feb91 |
| 4168 | Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc} |
| 4169 | may not be undefined. If you really detest this restriction we eagerly await |
| 4170 | a chance to share your improved assembler. |
| 4171 | |
| 4172 | Beware that the origin is relative to the start of the section, not |
| 4173 | to the start of the subsection. This is compatible with other |
| 4174 | people's assemblers. |
| 4175 | |
| 4176 | When the location counter (of the current subsection) is advanced, the |
| 4177 | intervening bytes are filled with @var{fill} which should be an |
| 4178 | absolute expression. If the comma and @var{fill} are omitted, |
| 4179 | @var{fill} defaults to zero. |
| 4180 | |
| 4181 | @node P2align |
| 4182 | @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}} |
| 4183 | |
| 4184 | @cindex padding the location counter given a power of two |
| 4185 | @cindex @code{p2align} directive |
| 4186 | Pad the location counter (in the current subsection) to a particular |
| 4187 | storage boundary. The first expression (which must be absolute) is the |
| 4188 | number of low-order zero bits the location counter must have after |
| 4189 | advancement. For example @samp{.p2align 3} advances the location |
| 4190 | counter until it a multiple of 8. If the location counter is already a |
| 4191 | multiple of 8, no change is needed. |
| 4192 | |
| 4193 | The second expression (also absolute) gives the fill value to be stored in the |
| 4194 | padding bytes. It (and the comma) may be omitted. If it is omitted, the |
| 4195 | padding bytes are normally zero. However, on some systems, if the section is |
| 4196 | marked as containing code and the fill value is omitted, the space is filled |
| 4197 | with no-op instructions. |
| 4198 | |
| 4199 | The third expression is also absolute, and is also optional. If it is present, |
| 4200 | it is the maximum number of bytes that should be skipped by this alignment |
| 4201 | directive. If doing the alignment would require skipping more bytes than the |
| 4202 | specified maximum, then the alignment is not done at all. You can omit the |
| 4203 | fill value (the second argument) entirely by simply using two commas after the |
| 4204 | required alignment; this can be useful if you want the alignment to be filled |
| 4205 | with no-op instructions when appropriate. |
| 4206 | |
| 4207 | @cindex @code{p2alignw} directive |
| 4208 | @cindex @code{p2alignl} directive |
| 4209 | The @code{.p2alignw} and @code{.p2alignl} directives are variants of the |
| 4210 | @code{.p2align} directive. The @code{.p2alignw} directive treats the fill |
| 4211 | pattern as a two byte word value. The @code{.p2alignl} directives treats the |
| 4212 | fill pattern as a four byte longword value. For example, @code{.p2alignw |
| 4213 | 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be |
| 4214 | filled in with the value 0x368d (the exact placement of the bytes depends upon |
| 4215 | the endianness of the processor). If it skips 1 or 3 bytes, the fill value is |
| 4216 | undefined. |
| 4217 | |
| 4218 | @node Print |
| 4219 | @section @code{.print @var{string}} |
| 4220 | |
| 4221 | @cindex @code{print} directive |
| 4222 | @code{@value{AS}} will print @var{string} on the standard output during |
| 4223 | assembly. You must put @var{string} in double quotes. |
| 4224 | |
| 4225 | @node Psize |
| 4226 | @section @code{.psize @var{lines} , @var{columns}} |
| 4227 | |
| 4228 | @cindex @code{psize} directive |
| 4229 | @cindex listing control: paper size |
| 4230 | @cindex paper size, for listings |
| 4231 | Use this directive to declare the number of lines---and, optionally, the |
| 4232 | number of columns---to use for each page, when generating listings. |
| 4233 | |
| 4234 | If you do not use @code{.psize}, listings use a default line-count |
| 4235 | of 60. You may omit the comma and @var{columns} specification; the |
| 4236 | default width is 200 columns. |
| 4237 | |
| 4238 | @code{@value{AS}} generates formfeeds whenever the specified number of |
| 4239 | lines is exceeded (or whenever you explicitly request one, using |
| 4240 | @code{.eject}). |
| 4241 | |
| 4242 | If you specify @var{lines} as @code{0}, no formfeeds are generated save |
| 4243 | those explicitly specified with @code{.eject}. |
| 4244 | |
| 4245 | @node Purgem |
| 4246 | @section @code{.purgem @var{name}} |
| 4247 | |
| 4248 | @cindex @code{purgem} directive |
| 4249 | Undefine the macro @var{name}, so that later uses of the string will not be |
| 4250 | expanded. @xref{Macro}. |
| 4251 | |
| 4252 | @node Quad |
| 4253 | @section @code{.quad @var{bignums}} |
| 4254 | |
| 4255 | @cindex @code{quad} directive |
| 4256 | @code{.quad} expects zero or more bignums, separated by commas. For |
| 4257 | each bignum, it emits |
| 4258 | @ifclear bignum-16 |
| 4259 | an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a |
| 4260 | warning message; and just takes the lowest order 8 bytes of the bignum. |
| 4261 | @cindex eight-byte integer |
| 4262 | @cindex integer, 8-byte |
| 4263 | |
| 4264 | The term ``quad'' comes from contexts in which a ``word'' is two bytes; |
| 4265 | hence @emph{quad}-word for 8 bytes. |
| 4266 | @end ifclear |
| 4267 | @ifset bignum-16 |
| 4268 | a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a |
| 4269 | warning message; and just takes the lowest order 16 bytes of the bignum. |
| 4270 | @cindex sixteen-byte integer |
| 4271 | @cindex integer, 16-byte |
| 4272 | @end ifset |
| 4273 | |
| 4274 | @node Rept |
| 4275 | @section @code{.rept @var{count}} |
| 4276 | |
| 4277 | @cindex @code{rept} directive |
| 4278 | Repeat the sequence of lines between the @code{.rept} directive and the next |
| 4279 | @code{.endr} directive @var{count} times. |
| 4280 | |
| 4281 | For example, assembling |
| 4282 | |
| 4283 | @example |
| 4284 | .rept 3 |
| 4285 | .long 0 |
| 4286 | .endr |
| 4287 | @end example |
| 4288 | |
| 4289 | is equivalent to assembling |
| 4290 | |
| 4291 | @example |
| 4292 | .long 0 |
| 4293 | .long 0 |
| 4294 | .long 0 |
| 4295 | @end example |
| 4296 | |
| 4297 | @node Sbttl |
| 4298 | @section @code{.sbttl "@var{subheading}"} |
| 4299 | |
| 4300 | @cindex @code{sbttl} directive |
| 4301 | @cindex subtitles for listings |
| 4302 | @cindex listing control: subtitle |
| 4303 | Use @var{subheading} as the title (third line, immediately after the |
| 4304 | title line) when generating assembly listings. |
| 4305 | |
| 4306 | This directive affects subsequent pages, as well as the current page if |
| 4307 | it appears within ten lines of the top of a page. |
| 4308 | |
| 4309 | @ifset COFF |
| 4310 | @node Scl |
| 4311 | @section @code{.scl @var{class}} |
| 4312 | |
| 4313 | @cindex @code{scl} directive |
| 4314 | @cindex symbol storage class (COFF) |
| 4315 | @cindex COFF symbol storage class |
| 4316 | Set the storage-class value for a symbol. This directive may only be |
| 4317 | used inside a @code{.def}/@code{.endef} pair. Storage class may flag |
| 4318 | whether a symbol is static or external, or it may record further |
| 4319 | symbolic debugging information. |
| 4320 | @ifset BOUT |
| 4321 | |
| 4322 | The @samp{.scl} directive is primarily associated with COFF output; when |
| 4323 | configured to generate @code{b.out} output format, @code{@value{AS}} |
| 4324 | accepts this directive but ignores it. |
| 4325 | @end ifset |
| 4326 | @end ifset |
| 4327 | |
| 4328 | @node Section |
| 4329 | @section @code{.section @var{name}} |
| 4330 | |
| 4331 | @cindex @code{section} directive |
| 4332 | @cindex named section |
| 4333 | Use the @code{.section} directive to assemble the following code into a section |
| 4334 | named @var{name}. |
| 4335 | |
| 4336 | This directive is only supported for targets that actually support arbitrarily |
| 4337 | named sections; on @code{a.out} targets, for example, it is not accepted, even |
| 4338 | with a standard @code{a.out} section name. |
| 4339 | |
| 4340 | @ifset COFF |
| 4341 | For COFF targets, the @code{.section} directive is used in one of the following |
| 4342 | ways: |
| 4343 | @smallexample |
| 4344 | .section @var{name}[, "@var{flags}"] |
| 4345 | .section @var{name}[, @var{subsegment}] |
| 4346 | @end smallexample |
| 4347 | |
| 4348 | If the optional argument is quoted, it is taken as flags to use for the |
| 4349 | section. Each flag is a single character. The following flags are recognized: |
| 4350 | @table @code |
| 4351 | @item b |
| 4352 | bss section (uninitialized data) |
| 4353 | @item n |
| 4354 | section is not loaded |
| 4355 | @item w |
| 4356 | writable section |
| 4357 | @item d |
| 4358 | data section |
| 4359 | @item r |
| 4360 | read-only section |
| 4361 | @item x |
| 4362 | executable section |
| 4363 | @item s |
| 4364 | shared section (meaningful for PE targets) |
| 4365 | @end table |
| 4366 | |
| 4367 | If no flags are specified, the default flags depend upon the section name. If |
| 4368 | the section name is not recognized, the default will be for the section to be |
| 4369 | loaded and writable. |
| 4370 | |
| 4371 | If the optional argument to the @code{.section} directive is not quoted, it is |
| 4372 | taken as a subsegment number (@pxref{Sub-Sections}). |
| 4373 | @end ifset |
| 4374 | |
| 4375 | @ifset ELF |
| 4376 | For ELF targets, the @code{.section} directive is used like this: |
| 4377 | @smallexample |
| 4378 | .section @var{name}[, "@var{flags}"[, @@@var{type}]] |
| 4379 | @end smallexample |
| 4380 | The optional @var{flags} argument is a quoted string which may contain any |
| 4381 | combintion of the following characters: |
| 4382 | @table @code |
| 4383 | @item a |
| 4384 | section is allocatable |
| 4385 | @item w |
| 4386 | section is writable |
| 4387 | @item x |
| 4388 | section is executable |
| 4389 | @end table |
| 4390 | |
| 4391 | The optional @var{type} argument may contain one of the following constants: |
| 4392 | @table @code |
| 4393 | @item @@progbits |
| 4394 | section contains data |
| 4395 | @item @@nobits |
| 4396 | section does not contain data (i.e., section only occupies space) |
| 4397 | @end table |
| 4398 | |
| 4399 | If no flags are specified, the default flags depend upon the section name. If |
| 4400 | the section name is not recognized, the default will be for the section to have |
| 4401 | none of the above flags: it will not be allocated in memory, nor writable, nor |
| 4402 | executable. The section will contain data. |
| 4403 | |
| 4404 | For ELF targets, the assembler supports another type of @code{.section} |
| 4405 | directive for compatibility with the Solaris assembler: |
| 4406 | @smallexample |
| 4407 | .section "@var{name}"[, @var{flags}...] |
| 4408 | @end smallexample |
| 4409 | Note that the section name is quoted. There may be a sequence of comma |
| 4410 | separated flags: |
| 4411 | @table @code |
| 4412 | @item #alloc |
| 4413 | section is allocatable |
| 4414 | @item #write |
| 4415 | section is writable |
| 4416 | @item #execinstr |
| 4417 | section is executable |
| 4418 | @end table |
| 4419 | @end ifset |
| 4420 | |
| 4421 | @node Set |
| 4422 | @section @code{.set @var{symbol}, @var{expression}} |
| 4423 | |
| 4424 | @cindex @code{set} directive |
| 4425 | @cindex symbol value, setting |
| 4426 | Set the value of @var{symbol} to @var{expression}. This |
| 4427 | changes @var{symbol}'s value and type to conform to |
| 4428 | @var{expression}. If @var{symbol} was flagged as external, it remains |
| 4429 | flagged (@pxref{Symbol Attributes}). |
| 4430 | |
| 4431 | You may @code{.set} a symbol many times in the same assembly. |
| 4432 | |
| 4433 | If you @code{.set} a global symbol, the value stored in the object |
| 4434 | file is the last value stored into it. |
| 4435 | |
| 4436 | @ifset HPPA |
| 4437 | The syntax for @code{set} on the HPPA is |
| 4438 | @samp{@var{symbol} .set @var{expression}}. |
| 4439 | @end ifset |
| 4440 | |
| 4441 | @node Short |
| 4442 | @section @code{.short @var{expressions}} |
| 4443 | |
| 4444 | @cindex @code{short} directive |
| 4445 | @ifset GENERIC |
| 4446 | @code{.short} is normally the same as @samp{.word}. |
| 4447 | @xref{Word,,@code{.word}}. |
| 4448 | |
| 4449 | In some configurations, however, @code{.short} and @code{.word} generate |
| 4450 | numbers of different lengths; @pxref{Machine Dependencies}. |
| 4451 | @end ifset |
| 4452 | @ifclear GENERIC |
| 4453 | @ifset W16 |
| 4454 | @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}. |
| 4455 | @end ifset |
| 4456 | @ifset W32 |
| 4457 | This expects zero or more @var{expressions}, and emits |
| 4458 | a 16 bit number for each. |
| 4459 | @end ifset |
| 4460 | @end ifclear |
| 4461 | |
| 4462 | @node Single |
| 4463 | @section @code{.single @var{flonums}} |
| 4464 | |
| 4465 | @cindex @code{single} directive |
| 4466 | @cindex floating point numbers (single) |
| 4467 | This directive assembles zero or more flonums, separated by commas. It |
| 4468 | has the same effect as @code{.float}. |
| 4469 | @ifset GENERIC |
| 4470 | The exact kind of floating point numbers emitted depends on how |
| 4471 | @code{@value{AS}} is configured. @xref{Machine Dependencies}. |
| 4472 | @end ifset |
| 4473 | @ifclear GENERIC |
| 4474 | @ifset IEEEFLOAT |
| 4475 | On the @value{TARGET} family, @code{.single} emits 32-bit floating point |
| 4476 | numbers in @sc{ieee} format. |
| 4477 | @end ifset |
| 4478 | @end ifclear |
| 4479 | |
| 4480 | @ifset COFF |
| 4481 | @node Size |
| 4482 | @section @code{.size} |
| 4483 | |
| 4484 | @cindex @code{size} directive |
| 4485 | This directive is generated by compilers to include auxiliary debugging |
| 4486 | information in the symbol table. It is only permitted inside |
| 4487 | @code{.def}/@code{.endef} pairs. |
| 4488 | @ifset BOUT |
| 4489 | |
| 4490 | @samp{.size} is only meaningful when generating COFF format output; when |
| 4491 | @code{@value{AS}} is generating @code{b.out}, it accepts this directive but |
| 4492 | ignores it. |
| 4493 | @end ifset |
| 4494 | @end ifset |
| 4495 | |
| 4496 | @node Sleb128 |
| 4497 | @section @code{.sleb128 @var{expressions}} |
| 4498 | |
| 4499 | @cindex @code{sleb128} directive |
| 4500 | @var{sleb128} stands for ``signed little endian base 128.'' This is a |
| 4501 | compact, variable length representation of numbers used by the DWARF |
| 4502 | symbolic debugging format. @xref{Uleb128,@code{.uleb128}}. |
| 4503 | |
| 4504 | @ifclear no-space-dir |
| 4505 | @node Skip |
| 4506 | @section @code{.skip @var{size} , @var{fill}} |
| 4507 | |
| 4508 | @cindex @code{skip} directive |
| 4509 | @cindex filling memory |
| 4510 | This directive emits @var{size} bytes, each of value @var{fill}. Both |
| 4511 | @var{size} and @var{fill} are absolute expressions. If the comma and |
| 4512 | @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as |
| 4513 | @samp{.space}. |
| 4514 | |
| 4515 | @node Space |
| 4516 | @section @code{.space @var{size} , @var{fill}} |
| 4517 | |
| 4518 | @cindex @code{space} directive |
| 4519 | @cindex filling memory |
| 4520 | This directive emits @var{size} bytes, each of value @var{fill}. Both |
| 4521 | @var{size} and @var{fill} are absolute expressions. If the comma |
| 4522 | and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same |
| 4523 | as @samp{.skip}. |
| 4524 | |
| 4525 | @ifset HPPA |
| 4526 | @quotation |
| 4527 | @emph{Warning:} @code{.space} has a completely different meaning for HPPA |
| 4528 | targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800 |
| 4529 | Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the |
| 4530 | @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives}, |
| 4531 | for a summary. |
| 4532 | @end quotation |
| 4533 | @end ifset |
| 4534 | @end ifclear |
| 4535 | |
| 4536 | @ifset A29K |
| 4537 | @ifclear GENERIC |
| 4538 | @node Space |
| 4539 | @section @code{.space} |
| 4540 | @cindex @code{space} directive |
| 4541 | @end ifclear |
| 4542 | On the AMD 29K, this directive is ignored; it is accepted for |
| 4543 | compatibility with other AMD 29K assemblers. |
| 4544 | |
| 4545 | @quotation |
| 4546 | @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive |
| 4547 | @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}. |
| 4548 | @end quotation |
| 4549 | @end ifset |
| 4550 | |
| 4551 | @ifset have-stabs |
| 4552 | @node Stab |
| 4553 | @section @code{.stabd, .stabn, .stabs} |
| 4554 | |
| 4555 | @cindex symbolic debuggers, information for |
| 4556 | @cindex @code{stab@var{x}} directives |
| 4557 | There are three directives that begin @samp{.stab}. |
| 4558 | All emit symbols (@pxref{Symbols}), for use by symbolic debuggers. |
| 4559 | The symbols are not entered in the @code{@value{AS}} hash table: they |
| 4560 | cannot be referenced elsewhere in the source file. |
| 4561 | Up to five fields are required: |
| 4562 | |
| 4563 | @table @var |
| 4564 | @item string |
| 4565 | This is the symbol's name. It may contain any character except |
| 4566 | @samp{\000}, so is more general than ordinary symbol names. Some |
| 4567 | debuggers used to code arbitrarily complex structures into symbol names |
| 4568 | using this field. |
| 4569 | |
| 4570 | @item type |
| 4571 | An absolute expression. The symbol's type is set to the low 8 bits of |
| 4572 | this expression. Any bit pattern is permitted, but @code{@value{LD}} |
| 4573 | and debuggers choke on silly bit patterns. |
| 4574 | |
| 4575 | @item other |
| 4576 | An absolute expression. The symbol's ``other'' attribute is set to the |
| 4577 | low 8 bits of this expression. |
| 4578 | |
| 4579 | @item desc |
| 4580 | An absolute expression. The symbol's descriptor is set to the low 16 |
| 4581 | bits of this expression. |
| 4582 | |
| 4583 | @item value |
| 4584 | An absolute expression which becomes the symbol's value. |
| 4585 | @end table |
| 4586 | |
| 4587 | If a warning is detected while reading a @code{.stabd}, @code{.stabn}, |
| 4588 | or @code{.stabs} statement, the symbol has probably already been created; |
| 4589 | you get a half-formed symbol in your object file. This is |
| 4590 | compatible with earlier assemblers! |
| 4591 | |
| 4592 | @table @code |
| 4593 | @cindex @code{stabd} directive |
| 4594 | @item .stabd @var{type} , @var{other} , @var{desc} |
| 4595 | |
| 4596 | The ``name'' of the symbol generated is not even an empty string. |
| 4597 | It is a null pointer, for compatibility. Older assemblers used a |
| 4598 | null pointer so they didn't waste space in object files with empty |
| 4599 | strings. |
| 4600 | |
| 4601 | The symbol's value is set to the location counter, |
| 4602 | relocatably. When your program is linked, the value of this symbol |
| 4603 | is the address of the location counter when the @code{.stabd} was |
| 4604 | assembled. |
| 4605 | |
| 4606 | @cindex @code{stabn} directive |
| 4607 | @item .stabn @var{type} , @var{other} , @var{desc} , @var{value} |
| 4608 | The name of the symbol is set to the empty string @code{""}. |
| 4609 | |
| 4610 | @cindex @code{stabs} directive |
| 4611 | @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value} |
| 4612 | All five fields are specified. |
| 4613 | @end table |
| 4614 | @end ifset |
| 4615 | @c end have-stabs |
| 4616 | |
| 4617 | @node String |
| 4618 | @section @code{.string} "@var{str}" |
| 4619 | |
| 4620 | @cindex string, copying to object file |
| 4621 | @cindex @code{string} directive |
| 4622 | |
| 4623 | Copy the characters in @var{str} to the object file. You may specify more than |
| 4624 | one string to copy, separated by commas. Unless otherwise specified for a |
| 4625 | particular machine, the assembler marks the end of each string with a 0 byte. |
| 4626 | You can use any of the escape sequences described in @ref{Strings,,Strings}. |
| 4627 | |
| 4628 | @node Struct |
| 4629 | @section @code{.struct @var{expression}} |
| 4630 | |
| 4631 | @cindex @code{struct} directive |
| 4632 | Switch to the absolute section, and set the section offset to @var{expression}, |
| 4633 | which must be an absolute expression. You might use this as follows: |
| 4634 | @smallexample |
| 4635 | .struct 0 |
| 4636 | field1: |
| 4637 | .struct field1 + 4 |
| 4638 | field2: |
| 4639 | .struct field2 + 4 |
| 4640 | field3: |
| 4641 | @end smallexample |
| 4642 | This would define the symbol @code{field1} to have the value 0, the symbol |
| 4643 | @code{field2} to have the value 4, and the symbol @code{field3} to have the |
| 4644 | value 8. Assembly would be left in the absolute section, and you would need to |
| 4645 | use a @code{.section} directive of some sort to change to some other section |
| 4646 | before further assembly. |
| 4647 | |
| 4648 | @ifset ELF |
| 4649 | @node Symver |
| 4650 | @section @code{.symver} |
| 4651 | @cindex @code{symver} directive |
| 4652 | @cindex symbol versioning |
| 4653 | @cindex versions of symbols |
| 4654 | Use the @code{.symver} directive to bind symbols to specific version nodes |
| 4655 | within a source file. This is only supported on ELF platforms, and is |
| 4656 | typically used when assembling files to be linked into a shared library. |
| 4657 | There are cases where it may make sense to use this in objects to be bound |
| 4658 | into an application itself so as to override a versioned symbol from a |
| 4659 | shared library. |
| 4660 | |
| 4661 | For ELF targets, the @code{.symver} directive is used like this: |
| 4662 | @smallexample |
| 4663 | .symver @var{name}, @var{name2@@nodename} |
| 4664 | @end smallexample |
| 4665 | In this case, the symbol @var{name} must exist and be defined within the file |
| 4666 | being assembled. The @code{.versym} directive effectively creates a symbol |
| 4667 | alias with the name @var{name2@@nodename}, and in fact the main reason that we |
| 4668 | just don't try and create a regular alias is that the @var{@@} character isn't |
| 4669 | permitted in symbol names. The @var{name2} part of the name is the actual name |
| 4670 | of the symbol by which it will be externally referenced. The name @var{name} |
| 4671 | itself is merely a name of convenience that is used so that it is possible to |
| 4672 | have definitions for multiple versions of a function within a single source |
| 4673 | file, and so that the compiler can unambiguously know which version of a |
| 4674 | function is being mentioned. The @var{nodename} portion of the alias should be |
| 4675 | the name of a node specified in the version script supplied to the linker when |
| 4676 | building a shared library. If you are attempting to override a versioned |
| 4677 | symbol from a shared library, then @var{nodename} should correspond to the |
| 4678 | nodename of the symbol you are trying to override. |
| 4679 | @end ifset |
| 4680 | |
| 4681 | @ifset COFF |
| 4682 | @node Tag |
| 4683 | @section @code{.tag @var{structname}} |
| 4684 | |
| 4685 | @cindex COFF structure debugging |
| 4686 | @cindex structure debugging, COFF |
| 4687 | @cindex @code{tag} directive |
| 4688 | This directive is generated by compilers to include auxiliary debugging |
| 4689 | information in the symbol table. It is only permitted inside |
| 4690 | @code{.def}/@code{.endef} pairs. Tags are used to link structure |
| 4691 | definitions in the symbol table with instances of those structures. |
| 4692 | @ifset BOUT |
| 4693 | |
| 4694 | @samp{.tag} is only used when generating COFF format output; when |
| 4695 | @code{@value{AS}} is generating @code{b.out}, it accepts this directive but |
| 4696 | ignores it. |
| 4697 | @end ifset |
| 4698 | @end ifset |
| 4699 | |
| 4700 | @node Text |
| 4701 | @section @code{.text @var{subsection}} |
| 4702 | |
| 4703 | @cindex @code{text} directive |
| 4704 | Tells @code{@value{AS}} to assemble the following statements onto the end of |
| 4705 | the text subsection numbered @var{subsection}, which is an absolute |
| 4706 | expression. If @var{subsection} is omitted, subsection number zero |
| 4707 | is used. |
| 4708 | |
| 4709 | @node Title |
| 4710 | @section @code{.title "@var{heading}"} |
| 4711 | |
| 4712 | @cindex @code{title} directive |
| 4713 | @cindex listing control: title line |
| 4714 | Use @var{heading} as the title (second line, immediately after the |
| 4715 | source file name and pagenumber) when generating assembly listings. |
| 4716 | |
| 4717 | This directive affects subsequent pages, as well as the current page if |
| 4718 | it appears within ten lines of the top of a page. |
| 4719 | |
| 4720 | @ifset COFF |
| 4721 | @node Type |
| 4722 | @section @code{.type @var{int}} |
| 4723 | |
| 4724 | @cindex COFF symbol type |
| 4725 | @cindex symbol type, COFF |
| 4726 | @cindex @code{type} directive |
| 4727 | This directive, permitted only within @code{.def}/@code{.endef} pairs, |
| 4728 | records the integer @var{int} as the type attribute of a symbol table entry. |
| 4729 | @ifset BOUT |
| 4730 | |
| 4731 | @samp{.type} is associated only with COFF format output; when |
| 4732 | @code{@value{AS}} is configured for @code{b.out} output, it accepts this |
| 4733 | directive but ignores it. |
| 4734 | @end ifset |
| 4735 | @end ifset |
| 4736 | |
| 4737 | @ifset COFF |
| 4738 | @node Val |
| 4739 | @section @code{.val @var{addr}} |
| 4740 | |
| 4741 | @cindex @code{val} directive |
| 4742 | @cindex COFF value attribute |
| 4743 | @cindex value attribute, COFF |
| 4744 | This directive, permitted only within @code{.def}/@code{.endef} pairs, |
| 4745 | records the address @var{addr} as the value attribute of a symbol table |
| 4746 | entry. |
| 4747 | @ifset BOUT |
| 4748 | |
| 4749 | @samp{.val} is used only for COFF output; when @code{@value{AS}} is |
| 4750 | configured for @code{b.out}, it accepts this directive but ignores it. |
| 4751 | @end ifset |
| 4752 | @end ifset |
| 4753 | |
| 4754 | @node Uleb128 |
| 4755 | @section @code{.uleb128 @var{expressions}} |
| 4756 | |
| 4757 | @cindex @code{uleb128} directive |
| 4758 | @var{uleb128} stands for ``unsigned little endian base 128.'' This is a |
| 4759 | compact, variable length representation of numbers used by the DWARF |
| 4760 | symbolic debugging format. @xref{Sleb128,@code{.sleb128}}. |
| 4761 | |
| 4762 | @ifset ELF |
| 4763 | @node Visibility |
| 4764 | @section @code{.internal}, @code{.hidden}, @code{.protected} |
| 4765 | @cindex @code{internal} directive |
| 4766 | @cindex @code{hidden} directive |
| 4767 | @cindex @code{protected} directive |
| 4768 | @cindex symbol visibility |
| 4769 | |
| 4770 | These directives can be used to set the visibility of a specified symbol. By |
| 4771 | default a symbol's visibility is set by its binding (local, global or weak), |
| 4772 | but these directives can be used to override that. |
| 4773 | |
| 4774 | A visibility of @code{protected} means that any references to the symbol from |
| 4775 | within the component that defines the symbol must be resolved to the definition |
| 4776 | in that component, even if a definition in another component would normally |
| 4777 | preempt this. |
| 4778 | |
| 4779 | A visibility of @code{hidden} means that the symbol is not visible to other |
| 4780 | components. Such a symbol is always considered to be protected as well. |
| 4781 | |
| 4782 | A visibility of @code{internal} is the same as a visibility of @code{hidden}, |
| 4783 | except that some extra, processor specific processing must also be performed |
| 4784 | upon the symbol. |
| 4785 | |
| 4786 | For ELF targets, the directives are used like this: |
| 4787 | |
| 4788 | @smallexample |
| 4789 | .internal @var{name} |
| 4790 | .hidden @var{name} |
| 4791 | .protected @var{name} |
| 4792 | @end smallexample |
| 4793 | |
| 4794 | @end ifset |
| 4795 | |
| 4796 | @node Word |
| 4797 | @section @code{.word @var{expressions}} |
| 4798 | |
| 4799 | @cindex @code{word} directive |
| 4800 | This directive expects zero or more @var{expressions}, of any section, |
| 4801 | separated by commas. |
| 4802 | @ifclear GENERIC |
| 4803 | @ifset W32 |
| 4804 | For each expression, @code{@value{AS}} emits a 32-bit number. |
| 4805 | @end ifset |
| 4806 | @ifset W16 |
| 4807 | For each expression, @code{@value{AS}} emits a 16-bit number. |
| 4808 | @end ifset |
| 4809 | @end ifclear |
| 4810 | @ifset GENERIC |
| 4811 | |
| 4812 | The size of the number emitted, and its byte order, |
| 4813 | depend on what target computer the assembly is for. |
| 4814 | @end ifset |
| 4815 | |
| 4816 | @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't |
| 4817 | @c happen---32-bit addressability, period; no long/short jumps. |
| 4818 | @ifset DIFF-TBL-KLUGE |
| 4819 | @cindex difference tables altered |
| 4820 | @cindex altered difference tables |
| 4821 | @quotation |
| 4822 | @emph{Warning: Special Treatment to support Compilers} |
| 4823 | @end quotation |
| 4824 | |
| 4825 | @ifset GENERIC |
| 4826 | Machines with a 32-bit address space, but that do less than 32-bit |
| 4827 | addressing, require the following special treatment. If the machine of |
| 4828 | interest to you does 32-bit addressing (or doesn't require it; |
| 4829 | @pxref{Machine Dependencies}), you can ignore this issue. |
| 4830 | |
| 4831 | @end ifset |
| 4832 | In order to assemble compiler output into something that works, |
| 4833 | @code{@value{AS}} occasionlly does strange things to @samp{.word} directives. |
| 4834 | Directives of the form @samp{.word sym1-sym2} are often emitted by |
| 4835 | compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a |
| 4836 | directive of the form @samp{.word sym1-sym2}, and the difference between |
| 4837 | @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}} |
| 4838 | creates a @dfn{secondary jump table}, immediately before the next label. |
| 4839 | This secondary jump table is preceded by a short-jump to the |
| 4840 | first byte after the secondary table. This short-jump prevents the flow |
| 4841 | of control from accidentally falling into the new table. Inside the |
| 4842 | table is a long-jump to @code{sym2}. The original @samp{.word} |
| 4843 | contains @code{sym1} minus the address of the long-jump to |
| 4844 | @code{sym2}. |
| 4845 | |
| 4846 | If there were several occurrences of @samp{.word sym1-sym2} before the |
| 4847 | secondary jump table, all of them are adjusted. If there was a |
| 4848 | @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a |
| 4849 | long-jump to @code{sym4} is included in the secondary jump table, |
| 4850 | and the @code{.word} directives are adjusted to contain @code{sym3} |
| 4851 | minus the address of the long-jump to @code{sym4}; and so on, for as many |
| 4852 | entries in the original jump table as necessary. |
| 4853 | |
| 4854 | @ifset INTERNALS |
| 4855 | @emph{This feature may be disabled by compiling @code{@value{AS}} with the |
| 4856 | @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse |
| 4857 | assembly language programmers. |
| 4858 | @end ifset |
| 4859 | @end ifset |
| 4860 | @c end DIFF-TBL-KLUGE |
| 4861 | |
| 4862 | @node Deprecated |
| 4863 | @section Deprecated Directives |
| 4864 | |
| 4865 | @cindex deprecated directives |
| 4866 | @cindex obsolescent directives |
| 4867 | One day these directives won't work. |
| 4868 | They are included for compatibility with older assemblers. |
| 4869 | @table @t |
| 4870 | @item .abort |
| 4871 | @item .line |
| 4872 | @end table |
| 4873 | |
| 4874 | @ifset GENERIC |
| 4875 | @node Machine Dependencies |
| 4876 | @chapter Machine Dependent Features |
| 4877 | |
| 4878 | @cindex machine dependencies |
| 4879 | The machine instruction sets are (almost by definition) different on |
| 4880 | each machine where @code{@value{AS}} runs. Floating point representations |
| 4881 | vary as well, and @code{@value{AS}} often supports a few additional |
| 4882 | directives or command-line options for compatibility with other |
| 4883 | assemblers on a particular platform. Finally, some versions of |
| 4884 | @code{@value{AS}} support special pseudo-instructions for branch |
| 4885 | optimization. |
| 4886 | |
| 4887 | This chapter discusses most of these differences, though it does not |
| 4888 | include details on any machine's instruction set. For details on that |
| 4889 | subject, see the hardware manufacturer's manual. |
| 4890 | |
| 4891 | @menu |
| 4892 | @ifset A29K |
| 4893 | * AMD29K-Dependent:: AMD 29K Dependent Features |
| 4894 | @end ifset |
| 4895 | @ifset ARC |
| 4896 | * ARC-Dependent:: ARC Dependent Features |
| 4897 | @end ifset |
| 4898 | @ifset ARM |
| 4899 | * ARM-Dependent:: ARM Dependent Features |
| 4900 | @end ifset |
| 4901 | @ifset D10V |
| 4902 | * D10V-Dependent:: D10V Dependent Features |
| 4903 | @end ifset |
| 4904 | @ifset D30V |
| 4905 | * D30V-Dependent:: D30V Dependent Features |
| 4906 | @end ifset |
| 4907 | @ifset H8/300 |
| 4908 | * H8/300-Dependent:: Hitachi H8/300 Dependent Features |
| 4909 | @end ifset |
| 4910 | @ifset H8/500 |
| 4911 | * H8/500-Dependent:: Hitachi H8/500 Dependent Features |
| 4912 | @end ifset |
| 4913 | @ifset HPPA |
| 4914 | * HPPA-Dependent:: HPPA Dependent Features |
| 4915 | @end ifset |
| 4916 | @ifset I80386 |
| 4917 | * i386-Dependent:: Intel 80386 Dependent Features |
| 4918 | @end ifset |
| 4919 | @ifset I960 |
| 4920 | * i960-Dependent:: Intel 80960 Dependent Features |
| 4921 | @end ifset |
| 4922 | @ifset M680X0 |
| 4923 | * M68K-Dependent:: M680x0 Dependent Features |
| 4924 | @end ifset |
| 4925 | @ifset MIPS |
| 4926 | * MIPS-Dependent:: MIPS Dependent Features |
| 4927 | @end ifset |
| 4928 | @ifset SH |
| 4929 | * SH-Dependent:: Hitachi SH Dependent Features |
| 4930 | @end ifset |
| 4931 | @ifset PJ |
| 4932 | * PJ-Dependent:: picoJava Dependent Features |
| 4933 | @end ifset |
| 4934 | @ifset SPARC |
| 4935 | * Sparc-Dependent:: SPARC Dependent Features |
| 4936 | @end ifset |
| 4937 | @ifset V850 |
| 4938 | * V850-Dependent:: V850 Dependent Features |
| 4939 | @end ifset |
| 4940 | @ifset Z8000 |
| 4941 | * Z8000-Dependent:: Z8000 Dependent Features |
| 4942 | @end ifset |
| 4943 | @ifset VAX |
| 4944 | * Vax-Dependent:: VAX Dependent Features |
| 4945 | @end ifset |
| 4946 | @end menu |
| 4947 | |
| 4948 | @lowersections |
| 4949 | @end ifset |
| 4950 | |
| 4951 | @c The following major nodes are *sections* in the GENERIC version, *chapters* |
| 4952 | @c in single-cpu versions. This is mainly achieved by @lowersections. There is a |
| 4953 | @c peculiarity: to preserve cross-references, there must be a node called |
| 4954 | @c "Machine Dependencies". Hence the conditional nodenames in each |
| 4955 | @c major node below. Node defaulting in makeinfo requires adjacency of |
| 4956 | @c node and sectioning commands; hence the repetition of @chapter BLAH |
| 4957 | @c in both conditional blocks. |
| 4958 | |
| 4959 | @ifset ARC |
| 4960 | @ifset GENERIC |
| 4961 | @page |
| 4962 | @node ARC-Dependent |
| 4963 | @chapter ARC Dependent Features |
| 4964 | @end ifset |
| 4965 | @ifclear GENERIC |
| 4966 | @node Machine Dependencies |
| 4967 | @chapter ARC Dependent Features |
| 4968 | @end ifclear |
| 4969 | |
| 4970 | @cindex ARC support |
| 4971 | @menu |
| 4972 | * ARC-Opts:: Options |
| 4973 | * ARC-Float:: Floating Point |
| 4974 | * ARC-Directives:: Sparc Machine Directives |
| 4975 | @end menu |
| 4976 | |
| 4977 | @node ARC-Opts |
| 4978 | @section Options |
| 4979 | |
| 4980 | @cindex options for ARC |
| 4981 | @cindex ARC options |
| 4982 | @cindex architectures, ARC |
| 4983 | @cindex ARC architectures |
| 4984 | The ARC chip family includes several successive levels (or other |
| 4985 | variants) of chip, using the same core instruction set, but including |
| 4986 | a few additional instructions at each level. |
| 4987 | |
| 4988 | By default, @code{@value{AS}} assumes the core instruction set (ARC |
| 4989 | base). The @code{.cpu} pseudo-op is intended to be used to select |
| 4990 | the variant. |
| 4991 | |
| 4992 | @table @code |
| 4993 | @cindex @code{-mbig-endian} option (ARC) |
| 4994 | @cindex @code{-mlittle-endian} option (ARC) |
| 4995 | @cindex ARC big-endian output |
| 4996 | @cindex ARC little-endian output |
| 4997 | @cindex big-endian output, ARC |
| 4998 | @cindex little-endian output, ARC |
| 4999 | @item -mbig-endian |
| 5000 | @itemx -mlittle-endian |
| 5001 | Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or |
| 5002 | little-endian output at run time (unlike most other @sc{gnu} development |
| 5003 | tools, which must be configured for one or the other). Use |
| 5004 | @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian} |
| 5005 | for little-endian. |
| 5006 | @end table |
| 5007 | |
| 5008 | @node ARC-Float |
| 5009 | @section Floating Point |
| 5010 | |
| 5011 | @cindex floating point, ARC (@sc{ieee}) |
| 5012 | @cindex ARC floating point (@sc{ieee}) |
| 5013 | The ARC cpu family currently does not have hardware floating point |
| 5014 | support. Software floating point support is provided by @code{GCC} |
| 5015 | and uses @sc{ieee} floating-point numbers. |
| 5016 | |
| 5017 | @node ARC-Directives |
| 5018 | @section ARC Machine Directives |
| 5019 | |
| 5020 | @cindex ARC machine directives |
| 5021 | @cindex machine directives, ARC |
| 5022 | The ARC version of @code{@value{AS}} supports the following additional |
| 5023 | machine directives: |
| 5024 | |
| 5025 | @table @code |
| 5026 | @item .cpu |
| 5027 | @cindex @code{cpu} directive, SPARC |
| 5028 | This must be followed by the desired cpu. |
| 5029 | The ARC is intended to be customizable, @code{.cpu} is used to |
| 5030 | select the desired variant [though currently there are none]. |
| 5031 | |
| 5032 | @end table |
| 5033 | |
| 5034 | @end ifset |
| 5035 | |
| 5036 | @ifset A29K |
| 5037 | @include c-a29k.texi |
| 5038 | @end ifset |
| 5039 | |
| 5040 | @ifset ARM |
| 5041 | @include c-arm.texi |
| 5042 | @end ifset |
| 5043 | |
| 5044 | @ifset Hitachi-all |
| 5045 | @ifclear GENERIC |
| 5046 | @node Machine Dependencies |
| 5047 | @chapter Machine Dependent Features |
| 5048 | |
| 5049 | The machine instruction sets are different on each Hitachi chip family, |
| 5050 | and there are also some syntax differences among the families. This |
| 5051 | chapter describes the specific @code{@value{AS}} features for each |
| 5052 | family. |
| 5053 | |
| 5054 | @menu |
| 5055 | * H8/300-Dependent:: Hitachi H8/300 Dependent Features |
| 5056 | * H8/500-Dependent:: Hitachi H8/500 Dependent Features |
| 5057 | * SH-Dependent:: Hitachi SH Dependent Features |
| 5058 | @end menu |
| 5059 | @lowersections |
| 5060 | @end ifclear |
| 5061 | @end ifset |
| 5062 | |
| 5063 | @ifset D10V |
| 5064 | @include c-d10v.texi |
| 5065 | @end ifset |
| 5066 | |
| 5067 | @ifset D30V |
| 5068 | @include c-d30v.texi |
| 5069 | @end ifset |
| 5070 | |
| 5071 | @ifset H8/300 |
| 5072 | @include c-h8300.texi |
| 5073 | @end ifset |
| 5074 | |
| 5075 | @ifset H8/500 |
| 5076 | @include c-h8500.texi |
| 5077 | @end ifset |
| 5078 | |
| 5079 | @ifset HPPA |
| 5080 | @include c-hppa.texi |
| 5081 | @end ifset |
| 5082 | |
| 5083 | @ifset I80386 |
| 5084 | @include c-i386.texi |
| 5085 | @end ifset |
| 5086 | |
| 5087 | @ifset I960 |
| 5088 | @include c-i960.texi |
| 5089 | @end ifset |
| 5090 | |
| 5091 | |
| 5092 | @ifset M680X0 |
| 5093 | @include c-m68k.texi |
| 5094 | @end ifset |
| 5095 | |
| 5096 | @ifset MIPS |
| 5097 | @include c-mips.texi |
| 5098 | @end ifset |
| 5099 | |
| 5100 | @ifset NS32K |
| 5101 | @include c-ns32k.texi |
| 5102 | @end ifset |
| 5103 | |
| 5104 | @ifset PJ |
| 5105 | @include c-pj.texi |
| 5106 | @end ifset |
| 5107 | |
| 5108 | @ifset SH |
| 5109 | @include c-sh.texi |
| 5110 | @end ifset |
| 5111 | |
| 5112 | @ifset SPARC |
| 5113 | @include c-sparc.texi |
| 5114 | @end ifset |
| 5115 | |
| 5116 | @ifset Z8000 |
| 5117 | @include c-z8k.texi |
| 5118 | @end ifset |
| 5119 | |
| 5120 | @ifset VAX |
| 5121 | @include c-vax.texi |
| 5122 | @end ifset |
| 5123 | |
| 5124 | @ifset V850 |
| 5125 | @include c-v850.texi |
| 5126 | @end ifset |
| 5127 | |
| 5128 | @ifset GENERIC |
| 5129 | @c reverse effect of @down at top of generic Machine-Dep chapter |
| 5130 | @raisesections |
| 5131 | @end ifset |
| 5132 | |
| 5133 | @node Reporting Bugs |
| 5134 | @chapter Reporting Bugs |
| 5135 | @cindex bugs in assembler |
| 5136 | @cindex reporting bugs in assembler |
| 5137 | |
| 5138 | Your bug reports play an essential role in making @code{@value{AS}} reliable. |
| 5139 | |
| 5140 | Reporting a bug may help you by bringing a solution to your problem, or it may |
| 5141 | not. But in any case the principal function of a bug report is to help the |
| 5142 | entire community by making the next version of @code{@value{AS}} work better. |
| 5143 | Bug reports are your contribution to the maintenance of @code{@value{AS}}. |
| 5144 | |
| 5145 | In order for a bug report to serve its purpose, you must include the |
| 5146 | information that enables us to fix the bug. |
| 5147 | |
| 5148 | @menu |
| 5149 | * Bug Criteria:: Have you found a bug? |
| 5150 | * Bug Reporting:: How to report bugs |
| 5151 | @end menu |
| 5152 | |
| 5153 | @node Bug Criteria |
| 5154 | @section Have you found a bug? |
| 5155 | @cindex bug criteria |
| 5156 | |
| 5157 | If you are not sure whether you have found a bug, here are some guidelines: |
| 5158 | |
| 5159 | @itemize @bullet |
| 5160 | @cindex fatal signal |
| 5161 | @cindex assembler crash |
| 5162 | @cindex crash of assembler |
| 5163 | @item |
| 5164 | If the assembler gets a fatal signal, for any input whatever, that is a |
| 5165 | @code{@value{AS}} bug. Reliable assemblers never crash. |
| 5166 | |
| 5167 | @cindex error on valid input |
| 5168 | @item |
| 5169 | If @code{@value{AS}} produces an error message for valid input, that is a bug. |
| 5170 | |
| 5171 | @cindex invalid input |
| 5172 | @item |
| 5173 | If @code{@value{AS}} does not produce an error message for invalid input, that |
| 5174 | is a bug. However, you should note that your idea of ``invalid input'' might |
| 5175 | be our idea of ``an extension'' or ``support for traditional practice''. |
| 5176 | |
| 5177 | @item |
| 5178 | If you are an experienced user of assemblers, your suggestions for improvement |
| 5179 | of @code{@value{AS}} are welcome in any case. |
| 5180 | @end itemize |
| 5181 | |
| 5182 | @node Bug Reporting |
| 5183 | @section How to report bugs |
| 5184 | @cindex bug reports |
| 5185 | @cindex assembler bugs, reporting |
| 5186 | |
| 5187 | A number of companies and individuals offer support for @sc{gnu} products. If |
| 5188 | you obtained @code{@value{AS}} from a support organization, we recommend you |
| 5189 | contact that organization first. |
| 5190 | |
| 5191 | You can find contact information for many support companies and |
| 5192 | individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs |
| 5193 | distribution. |
| 5194 | |
| 5195 | In any event, we also recommend that you send bug reports for @code{@value{AS}} |
| 5196 | to @samp{bug-gnu-utils@@gnu.org}. |
| 5197 | |
| 5198 | The fundamental principle of reporting bugs usefully is this: |
| 5199 | @strong{report all the facts}. If you are not sure whether to state a |
| 5200 | fact or leave it out, state it! |
| 5201 | |
| 5202 | Often people omit facts because they think they know what causes the problem |
| 5203 | and assume that some details do not matter. Thus, you might assume that the |
| 5204 | name of a symbol you use in an example does not matter. Well, probably it does |
| 5205 | not, but one cannot be sure. Perhaps the bug is a stray memory reference which |
| 5206 | happens to fetch from the location where that name is stored in memory; |
| 5207 | perhaps, if the name were different, the contents of that location would fool |
| 5208 | the assembler into doing the right thing despite the bug. Play it safe and |
| 5209 | give a specific, complete example. That is the easiest thing for you to do, |
| 5210 | and the most helpful. |
| 5211 | |
| 5212 | Keep in mind that the purpose of a bug report is to enable us to fix the bug if |
| 5213 | it is new to us. Therefore, always write your bug reports on the assumption |
| 5214 | that the bug has not been reported previously. |
| 5215 | |
| 5216 | Sometimes people give a few sketchy facts and ask, ``Does this ring a |
| 5217 | bell?'' Those bug reports are useless, and we urge everyone to |
| 5218 | @emph{refuse to respond to them} except to chide the sender to report |
| 5219 | bugs properly. |
| 5220 | |
| 5221 | To enable us to fix the bug, you should include all these things: |
| 5222 | |
| 5223 | @itemize @bullet |
| 5224 | @item |
| 5225 | The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start |
| 5226 | it with the @samp{--version} argument. |
| 5227 | |
| 5228 | Without this, we will not know whether there is any point in looking for |
| 5229 | the bug in the current version of @code{@value{AS}}. |
| 5230 | |
| 5231 | @item |
| 5232 | Any patches you may have applied to the @code{@value{AS}} source. |
| 5233 | |
| 5234 | @item |
| 5235 | The type of machine you are using, and the operating system name and |
| 5236 | version number. |
| 5237 | |
| 5238 | @item |
| 5239 | What compiler (and its version) was used to compile @code{@value{AS}}---e.g. |
| 5240 | ``@code{gcc-2.7}''. |
| 5241 | |
| 5242 | @item |
| 5243 | The command arguments you gave the assembler to assemble your example and |
| 5244 | observe the bug. To guarantee you will not omit something important, list them |
| 5245 | all. A copy of the Makefile (or the output from make) is sufficient. |
| 5246 | |
| 5247 | If we were to try to guess the arguments, we would probably guess wrong |
| 5248 | and then we might not encounter the bug. |
| 5249 | |
| 5250 | @item |
| 5251 | A complete input file that will reproduce the bug. If the bug is observed when |
| 5252 | the assembler is invoked via a compiler, send the assembler source, not the |
| 5253 | high level language source. Most compilers will produce the assembler source |
| 5254 | when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use |
| 5255 | the options @samp{-v --save-temps}; this will save the assembler source in a |
| 5256 | file with an extension of @file{.s}, and also show you exactly how |
| 5257 | @code{@value{AS}} is being run. |
| 5258 | |
| 5259 | @item |
| 5260 | A description of what behavior you observe that you believe is |
| 5261 | incorrect. For example, ``It gets a fatal signal.'' |
| 5262 | |
| 5263 | Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we |
| 5264 | will certainly notice it. But if the bug is incorrect output, we might not |
| 5265 | notice unless it is glaringly wrong. You might as well not give us a chance to |
| 5266 | make a mistake. |
| 5267 | |
| 5268 | Even if the problem you experience is a fatal signal, you should still say so |
| 5269 | explicitly. Suppose something strange is going on, such as, your copy of |
| 5270 | @code{@value{AS}} is out of synch, or you have encountered a bug in the C |
| 5271 | library on your system. (This has happened!) Your copy might crash and ours |
| 5272 | would not. If you told us to expect a crash, then when ours fails to crash, we |
| 5273 | would know that the bug was not happening for us. If you had not told us to |
| 5274 | expect a crash, then we would not be able to draw any conclusion from our |
| 5275 | observations. |
| 5276 | |
| 5277 | @item |
| 5278 | If you wish to suggest changes to the @code{@value{AS}} source, send us context |
| 5279 | diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p} |
| 5280 | option. Always send diffs from the old file to the new file. If you even |
| 5281 | discuss something in the @code{@value{AS}} source, refer to it by context, not |
| 5282 | by line number. |
| 5283 | |
| 5284 | The line numbers in our development sources will not match those in your |
| 5285 | sources. Your line numbers would convey no useful information to us. |
| 5286 | @end itemize |
| 5287 | |
| 5288 | Here are some things that are not necessary: |
| 5289 | |
| 5290 | @itemize @bullet |
| 5291 | @item |
| 5292 | A description of the envelope of the bug. |
| 5293 | |
| 5294 | Often people who encounter a bug spend a lot of time investigating |
| 5295 | which changes to the input file will make the bug go away and which |
| 5296 | changes will not affect it. |
| 5297 | |
| 5298 | This is often time consuming and not very useful, because the way we |
| 5299 | will find the bug is by running a single example under the debugger |
| 5300 | with breakpoints, not by pure deduction from a series of examples. |
| 5301 | We recommend that you save your time for something else. |
| 5302 | |
| 5303 | Of course, if you can find a simpler example to report @emph{instead} |
| 5304 | of the original one, that is a convenience for us. Errors in the |
| 5305 | output will be easier to spot, running under the debugger will take |
| 5306 | less time, and so on. |
| 5307 | |
| 5308 | However, simplification is not vital; if you do not want to do this, |
| 5309 | report the bug anyway and send us the entire test case you used. |
| 5310 | |
| 5311 | @item |
| 5312 | A patch for the bug. |
| 5313 | |
| 5314 | A patch for the bug does help us if it is a good one. But do not omit |
| 5315 | the necessary information, such as the test case, on the assumption that |
| 5316 | a patch is all we need. We might see problems with your patch and decide |
| 5317 | to fix the problem another way, or we might not understand it at all. |
| 5318 | |
| 5319 | Sometimes with a program as complicated as @code{@value{AS}} it is very hard to |
| 5320 | construct an example that will make the program follow a certain path through |
| 5321 | the code. If you do not send us the example, we will not be able to construct |
| 5322 | one, so we will not be able to verify that the bug is fixed. |
| 5323 | |
| 5324 | And if we cannot understand what bug you are trying to fix, or why your |
| 5325 | patch should be an improvement, we will not install it. A test case will |
| 5326 | help us to understand. |
| 5327 | |
| 5328 | @item |
| 5329 | A guess about what the bug is or what it depends on. |
| 5330 | |
| 5331 | Such guesses are usually wrong. Even we cannot guess right about such |
| 5332 | things without first using the debugger to find the facts. |
| 5333 | @end itemize |
| 5334 | |
| 5335 | @node Acknowledgements |
| 5336 | @chapter Acknowledgements |
| 5337 | |
| 5338 | If you have contributed to @code{@value{AS}} and your name isn't listed here, |
| 5339 | it is not meant as a slight. We just don't know about it. Send mail to the |
| 5340 | maintainer, and we'll correct the situation. Currently |
| 5341 | @c (January 1994), |
| 5342 | the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}). |
| 5343 | |
| 5344 | Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any |
| 5345 | more details?} |
| 5346 | |
| 5347 | Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug |
| 5348 | information and the 68k series machines, most of the preprocessing pass, and |
| 5349 | extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}. |
| 5350 | |
| 5351 | K. Richard Pixley maintained GAS for a while, adding various enhancements and |
| 5352 | many bug fixes, including merging support for several processors, breaking GAS |
| 5353 | up to handle multiple object file format back ends (including heavy rewrite, |
| 5354 | testing, an integration of the coff and b.out back ends), adding configuration |
| 5355 | including heavy testing and verification of cross assemblers and file splits |
| 5356 | and renaming, converted GAS to strictly ANSI C including full prototypes, added |
| 5357 | support for m680[34]0 and cpu32, did considerable work on i960 including a COFF |
| 5358 | port (including considerable amounts of reverse engineering), a SPARC opcode |
| 5359 | file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know'' |
| 5360 | assertions and made them work, much other reorganization, cleanup, and lint. |
| 5361 | |
| 5362 | Ken Raeburn wrote the high-level BFD interface code to replace most of the code |
| 5363 | in format-specific I/O modules. |
| 5364 | |
| 5365 | The original VMS support was contributed by David L. Kashtan. Eric Youngdale |
| 5366 | has done much work with it since. |
| 5367 | |
| 5368 | The Intel 80386 machine description was written by Eliot Dresselhaus. |
| 5369 | |
| 5370 | Minh Tran-Le at IntelliCorp contributed some AIX 386 support. |
| 5371 | |
| 5372 | The Motorola 88k machine description was contributed by Devon Bowen of Buffalo |
| 5373 | University and Torbjorn Granlund of the Swedish Institute of Computer Science. |
| 5374 | |
| 5375 | Keith Knowles at the Open Software Foundation wrote the original MIPS back end |
| 5376 | (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support |
| 5377 | (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to |
| 5378 | support a.out format. |
| 5379 | |
| 5380 | Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k, |
| 5381 | tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by |
| 5382 | Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to |
| 5383 | use BFD for some low-level operations, for use with the H8/300 and AMD 29k |
| 5384 | targets. |
| 5385 | |
| 5386 | John Gilmore built the AMD 29000 support, added @code{.include} support, and |
| 5387 | simplified the configuration of which versions accept which directives. He |
| 5388 | updated the 68k machine description so that Motorola's opcodes always produced |
| 5389 | fixed-size instructions (e.g. @code{jsr}), while synthetic instructions |
| 5390 | remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested |
| 5391 | cross-compilation support, and one bug in relaxation that took a week and |
| 5392 | required the proverbial one-bit fix. |
| 5393 | |
| 5394 | Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the |
| 5395 | 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix), |
| 5396 | added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and |
| 5397 | PowerPC assembler, and made a few other minor patches. |
| 5398 | |
| 5399 | Steve Chamberlain made @code{@value{AS}} able to generate listings. |
| 5400 | |
| 5401 | Hewlett-Packard contributed support for the HP9000/300. |
| 5402 | |
| 5403 | Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM) |
| 5404 | along with a fairly extensive HPPA testsuite (for both SOM and ELF object |
| 5405 | formats). This work was supported by both the Center for Software Science at |
| 5406 | the University of Utah and Cygnus Support. |
| 5407 | |
| 5408 | Support for ELF format files has been worked on by Mark Eichin of Cygnus |
| 5409 | Support (original, incomplete implementation for SPARC), Pete Hoogenboom and |
| 5410 | Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open |
| 5411 | Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc, |
| 5412 | and some initial 64-bit support). |
| 5413 | |
| 5414 | Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD |
| 5415 | support for openVMS/Alpha. |
| 5416 | |
| 5417 | Several engineers at Cygnus Support have also provided many small bug fixes and |
| 5418 | configuration enhancements. |
| 5419 | |
| 5420 | Many others have contributed large or small bugfixes and enhancements. If |
| 5421 | you have contributed significant work and are not mentioned on this list, and |
| 5422 | want to be, let us know. Some of the history has been lost; we are not |
| 5423 | intentionally leaving anyone out. |
| 5424 | |
| 5425 | @node Index |
| 5426 | @unnumbered Index |
| 5427 | |
| 5428 | @printindex cp |
| 5429 | |
| 5430 | @contents |
| 5431 | @bye |
| 5432 | @c Local Variables: |
| 5433 | @c fill-column: 79 |
| 5434 | @c End: |