ld/ld.1

   1 .\" Copyright (c) 1991, 92, 93, 94, 1995 Free Software Foundation
   2 .\" See section COPYING for conditions for redistribution
   3 .TH ld 1 "17 August 1992" "cygnus support" "GNU Development Tools"
   4 .de BP
   5 .sp
   6 .ti \-.2i
   7 \(**
   8 ..
   9
  10 .SH NAME
  11 ld \- the GNU linker
  12
  13 .SH SYNOPSIS
  14 .hy 0
  15 .na
  16 .TP
  17 .B ld
  18 .RB "[\|" \-o "
  19 .I output\c
  20 \&\|] \c
  21 .I objfile\c
  22 \&.\|.\|.
  23 .br
  24 .RB "[\|" \-A\c
  25 .I architecture\c
  26 \&\|]
  27 .RB "[\|" "\-b\ "\c
  28 .I input-format\c
  29 \&\|]
  30 .RB "[\|" \-Bstatic "\|]"
  31 .RB "[\|" \-Bdynamic "\|]"
  32 .RB "[\|" \-Bsymbolic "\|]"
  33 .RB "[\|" "\-c\ "\c
  34 .I commandfile\c
  35 \&\|]
  36 .RB "[\|" \-d | \-dc | \-dp\c
  37 \|]
  38 .br
  39 .RB "[\|" "\-defsym\ "\c
  40 .I symbol\c
  41 \& = \c
  42 .I expression\c
  43 \&\|]
  44 .RB "[\|" "\-e\ "\c
  45 .I entry\c
  46 \&\|]
  47 .RB "[\|" \-embedded\-relocs "\|]"
  48 .RB "[\|" \-F "\|]"
  49 .RB "[\|" "\-F\ "\c
  50 .I format\c
  51 \&\|]
  52 .RB "[\|" "\-format\ "\c
  53 .I input-format\c
  54 \&\|]
  55 .RB "[\|" \-g "\|]"
  56 .RB "[\|" \-G\c
  57 .I size\c
  58 \&\|]
  59 .RB "[\|" \-\-help "\|]"
  60 .RB "[\|" \-i "\|]"
  61 .RB "[\|" \-l\c
  62 .I ar\c
  63 \&\|]
  64 .RB "[\|" \-L\c
  65 .I searchdir\c
  66 \&\|]
  67 .RB "[\|" \-M "\|]"
  68 .RB "[\|" \-Map\c
  69 .I mapfile\c
  70 \&\|]
  71 .RB "[\|" \-m\c
  72 .I emulation\c
  73 \&\|]
  74 .RB "[\|" \-n | \-N "\|]"
  75 .RB "[\|" \-noinhibit-exec "\|]"
  76 .RB "[\|" \-no\-keep\-memory "\|]"
  77 .RB "[\|" "\-oformat\ "\c
  78 .I output-format\c
  79 \&\|]
  80 .RB "[\|" "\-R\ "\c
  81 .I filename\c
  82 \&\|]
  83 .RB "[\|" \-relax "\|]"
  84 .RB "[\|" \-r | \-Ur "\|]"
  85 .RB "[\|" \-S "\|]"
  86 .RB "[\|" \-s "\|]"
  87 .RB "[\|" \-shared "\|]"
  88 .RB "[\|" \-sort\-common "\|]"
  89 .RB "[\|" \-split\-by\-reloc\ "\c
  90 .I count\c
  91 \&\|]
  92 .RB "[\|" \-split\-by\-file "\|]"
  93 .RB "[\|" "\-T\ "\c
  94 .I commandfile\c
  95 \&\|]
  96 .RB "[\|" "\-Ttext\ "\c
  97 .I textorg\c
  98 \&\|]
  99 .RB "[\|" "\-Tdata\ "\c
 100 .I dataorg\c
 101 \&\|]
 102 .RB "[\|" "\-Tbss\ "\c
 103 .I bssorg\c
 104 \&\|]
 105 .RB "[\|" \-t "\|]"
 106 .RB "[\|" "\-u\ "\c
 107 .I sym\c
 108 \&]
 109 .RB "[\|" \-V "\|]"
 110 .RB "[\|" \-v "\|]"
 111 .RB "[\|" \-\-verbose "\|]"
 112 .RB "[\|" \-\-version "\|]"
 113 .RB "[\|" \-warn\-common "\|]"
 114 .RB "[\|" \-warn\-constructors "\|]"
 115 .RB "[\|" \-warn\-once "\|]"
 116 .RB "[\|" \-\-whole\-archive "\|]"
 117 .RB "[\|" \-X "\|]"
 118 .RB "[\|" \-x "\|]"
 119 .ad b
 120 .hy 1
 121 .SH DESCRIPTION
 122 \c
 123 .B ld\c
 124 \& combines a number of object and archive files, relocates
 125 their data and ties up symbol references. Often the last step in
 126 building a new compiled program to run is a call to \c
 127 .B ld\c
 128 \&.
 129
 130 \c
 131 .B ld\c
 132 \& accepts Linker Command Language files
 133 to provide explicit and total control over the linking process.
 134 This man page does not describe the command language; see the `\|\c
 135 .B ld\c
 136 \|' entry in `\|\c
 137 .B info\c
 138 \|', or the manual
 139 .I
 140 ld: the GNU linker
 141 \&, for full details on the command language and on other aspects of
 142 the GNU linker.
 143
 144 This version of \c
 145 .B ld\c
 146 \& uses the general purpose BFD libraries
 147 to operate on object files. This allows \c
 148 .B ld\c
 149 \& to read, combine, and
 150 write object files in many different formats\(em\&for example, COFF or
 151 \c
 152 .B a.out\c
 153 \&.  Different formats may be linked together to produce any
 154 available kind of object file.  You can use `\|\c
 155 .B objdump \-i\c
 156 \|' to get a list of formats supported on various architectures; see
 157 .BR objdump ( 1 ).
 158
 159 Aside from its flexibility, the GNU linker is more helpful than other
 160 linkers in providing diagnostic information.  Many linkers abandon
 161 execution immediately upon encountering an error; whenever possible,
 162 \c
 163 .B ld\c
 164 \& continues executing, allowing you to identify other errors
 165 (or, in some cases, to get an output file in spite of the error).
 166
 167 The GNU linker \c
 168 .B ld\c
 169 \& is meant to cover a broad range of situations,
 170 and to be as compatible as possible with other linkers.  As a result,
 171 you have many choices to control its behavior through the command line,
 172 and through environment variables.
 173
 174 .SH OPTIONS
 175 The plethora of command-line options may seem intimidating, but in
 176 actual practice few of them are used in any particular context.
 177 For instance, a frequent use of \c
 178 .B ld\c
 179 \& is to link standard Unix
 180 object files on a standard, supported Unix system.  On such a system, to
 181 link a file \c
 182 .B hello.o\c
 183 \&:
 184 .sp
 185 .br
 186 $\ ld\ \-o\ output\ /lib/crt0.o\ hello.o\ \-lc
 187 .br
 188 .sp
 189 This tells \c
 190 .B ld\c
 191 \& to produce a file called \c
 192 .B output\c
 193 \& as the
 194 result of linking the file \c
 195 .B /lib/crt0.o\c
 196 \& with \c
 197 .B hello.o\c
 198 \& and
 199 the library \c
 200 .B libc.a\c
 201 \& which will come from the standard search
 202 directories.
 203
 204 The command-line options to \c
 205 .B ld\c
 206 \& may be specified in any order, and
 207 may be repeated at will.  For the most part, repeating an option with a
 208 different argument will either have no further effect, or override prior
 209 occurrences (those further to the left on the command line) of an
 210 option.
 211
 212 The exceptions\(em\&which may meaningfully be used more than once\(em\&are
 213 \c
 214 .B \-A\c
 215 \&, \c
 216 .B \-b\c
 217 \& (or its synonym \c
 218 .B \-format\c
 219 \&), \c
 220 .B \-defsym\c
 221 \&,
 222 \c
 223 .B \-L\c
 224 \&, \c
 225 .B \-l\c
 226 \&, \c
 227 .B \-R\c
 228 \&, and \c
 229 .B \-u\c
 230 \&.
 231
 232 The list of object files to be linked together, shown as \c
 233 .I objfile\c
 234 \&,
 235 may follow, precede, or be mixed in with command-line options; save that
 236 an \c
 237 .I objfile\c
 238 \& argument may not be placed between an option flag and
 239 its argument.
 240
 241 Usually the linker is invoked with at least one object file, but other
 242 forms of binary input files can also be specified with \c
 243 .B \-l\c
 244 \&,
 245 \c
 246 .B \-R\c
 247 \&, and the script command language.  If \c
 248 .I no\c
 249 \& binary input
 250 files at all are specified, the linker does not produce any output, and
 251 issues the message `\|\c
 252 .B No input files\c
 253 \|'.
 254
 255 Option arguments must either follow the option letter without intervening
 256 whitespace, or be given as separate arguments immediately following the
 257 option that requires them.
 258
 259 .TP
 260 .BI "-A" "architecture"\c
 261 \&
 262 In the current release of \c
 263 .B ld\c
 264 \&, this option is useful only for the
 265 Intel 960 family of architectures.  In that \c
 266 .B ld\c
 267 \& configuration, the
 268 \c
 269 .I architecture\c
 270 \& argument is one of the two-letter names identifying
 271 members of the 960 family; the option specifies the desired output
 272 target, and warns of any incompatible instructions in the input files.
 273 It also modifies the linker's search strategy for archive libraries, to
 274 support the use of libraries specific to each particular
 275 architecture, by including in the search loop names suffixed with the
 276 string identifying the architecture.
 277
 278 For example, if your \c
 279 .B ld\c
 280 \& command line included `\|\c
 281 .B \-ACA\c
 282 \|' as
 283 well as `\|\c
 284 .B \-ltry\c
 285 \|', the linker would look (in its built-in search
 286 paths, and in any paths you specify with \c
 287 .B \-L\c
 288 \&) for a library with
 289 the names
 290 .sp
 291 .br
 292 try
 293 .br
 294 libtry.a
 295 .br
 296 tryca
 297 .br
 298 libtryca.a
 299 .br
 300 .sp
 301
 302 The first two possibilities would be considered in any event; the last
 303 two are due to the use of `\|\c
 304 .B \-ACA\c
 305 \|'.
 306
 307 Future releases of \c
 308 .B ld\c
 309 \& may support similar functionality for
 310 other architecture families.
 311
 312 You can meaningfully use \c
 313 .B \-A\c
 314 \& more than once on a command line, if
 315 an architecture family allows combination of target architectures; each
 316 use will add another pair of name variants to search for when \c
 317 .B \-l\c
 318 \&
 319 specifies a library.
 320
 321 .TP
 322 .BI "\-b " "input-format"\c
 323 \&
 324 Specify the binary format for input object files that follow this option
 325 on the command line.  You don't usually need to specify this, as
 326 \c
 327 .B ld\c
 328 \& is configured to expect as a default input format the most
 329 usual format on each machine.  \c
 330 .I input-format\c
 331 \& is a text string, the
 332 name of a particular format supported by the BFD libraries.
 333 \c
 334 .B \-format \c
 335 .I input-format\c
 336 \&\c
 337 \& has the same effect, as does the script command
 338 .BR TARGET .
 339
 340 You may want to use this option if you are linking files with an unusual
 341 binary format.  You can also use \c
 342 .B \-b\c
 343 \& to switch formats explicitly (when
 344 linking object files of different formats), by including
 345 \c
 346 .B \-b \c
 347 .I input-format\c
 348 \&\c
 349 \& before each group of object files in a
 350 particular format.
 351
 352 The default format is taken from the environment variable
 353 .B GNUTARGET\c
 354 \&.  You can also define the input
 355 format from a script, using the command \c
 356 .B TARGET\c
 357 \&.
 358
 359 .TP
 360 .B \-Bstatic
 361 Do not link against shared libraries.  This is only meaningful on
 362 platforms for which shared libraries are supported.
 363
 364 .TP
 365 .B \-Bdynamic
 366 Link against dynamic libraries.  This is only meaningful on platforms
 367 for which shared libraries are supported.  This option is normally the
 368 default on such platforms.
 369
 370 .TP
 371 .B \-Bsymbolic
 372 When creating a shared library, bind references to global symbols to
 373 the definition within the shared library, if any.  Normally, it is
 374 possible for a program linked against a shared library to override the
 375 definition within the shared library.  This option is only meaningful
 376 on ELF platforms which support shared libraries.
 377
 378 .TP
 379 .BI "\-c " "commandfile"\c
 380 \&
 381 Directs \c
 382 .B ld\c
 383 \& to read link commands from the file
 384 \c
 385 .I commandfile\c
 386 \&.  These commands will completely override \c
 387 .B ld\c
 388 \&'s
 389 default link format (rather than adding to it); \c
 390 .I commandfile\c
 391 \& must
 392 specify everything necessary to describe the target format.
 393
 394
 395 You may also include a script of link commands directly in the command
 396 line by bracketing it between `\|\c
 397 .B {\c
 398 \|' and `\|\c
 399 .B }\c
 400 \|' characters.
 401
 402 .TP
 403 .B \-d
 404 .TP
 405 .B \-dc
 406 .TP
 407 .B \-dp
 408 These three options are equivalent; multiple forms are supported for
 409 compatibility with other linkers.  Use any of them to make \c
 410 .B ld\c
 411 \&
 412 assign space to common symbols even if a relocatable output file is
 413 specified (\c
 414 .B \-r\c
 415 \&).  The script command
 416 \c
 417 .B FORCE_COMMON_ALLOCATION\c
 418 \& has the same effect.
 419
 420 .TP
 421 .BI "-defsym " "symbol"\c
 422 \& = \c
 423 .I expression\c
 424 \&
 425 Create a global symbol in the output file, containing the absolute
 426 address given by \c
 427 .I expression\c
 428 \&.  You may use this option as many
 429 times as necessary to define multiple symbols in the command line.  A
 430 limited form of arithmetic is supported for the \c
 431 .I expression\c
 432 \& in this
 433 context: you may give a hexadecimal constant or the name of an existing
 434 symbol, or use \c
 435 .B +\c
 436 \& and \c
 437 .B \-\c
 438 \& to add or subtract hexadecimal
 439 constants or symbols.  If you need more elaborate expressions, consider
 440 using the linker command language from a script.
 441
 442 .TP
 443 .BI "-e " "entry"\c
 444 \&
 445 Use \c
 446 .I entry\c
 447 \& as the explicit symbol for beginning execution of your
 448 program, rather than the default entry point.  for a
 449 discussion of defaults and other ways of specifying the
 450 entry point.
 451
 452 .TP
 453 .B \-embedded\-relocs
 454 This option is only meaningful when linking MIPS embedded PIC code,
 455 generated by the
 456 .B \-membedded\-pic
 457 option to the GNU compiler and assembler.  It causes the linker to
 458 create a table which may be used at runtime to relocate any data which
 459 was statically initialized to pointer values.  See the code in
 460 testsuite/ld-empic for details.
 461
 462 .TP
 463 .B \-F
 464 .TP
 465 .BI "-F" "format"\c
 466 \&
 467 Some older linkers used this option throughout a compilation toolchain
 468 for specifying object-file format for both input and output object
 469 files.  \c
 470 .B ld\c
 471 \&'s mechanisms (the \c
 472 .B \-b\c
 473 \& or \c
 474 .B \-format\c
 475 \& options
 476 for input files, the \c
 477 .B TARGET\c
 478 \& command in linker scripts for output
 479 files, the \c
 480 .B GNUTARGET\c
 481 \& environment variable) are more flexible, but
 482 but it accepts (and ignores) the \c
 483 .B \-F\c
 484 \& option flag for compatibility
 485 with scripts written to call the old linker.
 486
 487 .TP
 488 .BI "\-format " "input\-format"\c
 489 \&
 490 Synonym for \c
 491 .B \-b\c
 492 \& \c
 493 .I input\-format\c
 494 \&.
 495
 496 .TP
 497 .B \-g
 498 Accepted, but ignored; provided for compatibility with other tools.
 499
 500 .TP
 501 .BI "\-G " "size"\c
 502 Set the maximum size of objects to be optimized using the GP register
 503 to
 504 .I size
 505 under MIPS ECOFF.  Ignored for other object file formats.
 506
 507 .TP
 508 .B \-\-help
 509 Print a summary of the command-line options on the standard output and exit.
 510 This option and
 511 .B \-\-version
 512 begin with two dashes instead of one
 513 for compatibility with other GNU programs.  The other options start with
 514 only one dash for compatibility with other linkers.
 515
 516 .TP
 517 .B \-i
 518 Perform an incremental link (same as option \c
 519 .B \-r\c
 520 \&).
 521
 522 .TP
 523 .BI "\-l" "ar"\c
 524 \&
 525 Add an archive file \c
 526 .I ar\c
 527 \& to the list of files to link.  This
 528 option may be used any number of times.  \c
 529 .B ld\c
 530 \& will search its
 531 path-list for occurrences of \c
 532 .B lib\c
 533 .I ar\c
 534 \&.a\c
 535 \& for every \c
 536 .I ar\c
 537 \&
 538 specified.
 539
 540 .TP
 541 .BI "\-L" "searchdir"\c
 542 \&
 543 This command adds path \c
 544 .I searchdir\c
 545 \& to the list of paths that
 546 \c
 547 .B ld\c
 548 \& will search for archive libraries.  You may use this option
 549 any number of times.
 550
 551 The default set of paths searched (without being specified with
 552 \c
 553 .B \-L\c
 554 \&) depends on what emulation mode \c
 555 .B ld\c
 556 \& is using, and in
 557 some cases also on how it was configured.    The
 558 paths can also be specified in a link script with the \c
 559 .B SEARCH_DIR\c
 560 \&
 561 command.
 562
 563 .TP
 564 .B \-M
 565 Print (to the standard output file) a link map\(em\&diagnostic information
 566 about where symbols are mapped by \c
 567 .B ld\c
 568 \&, and information on global
 569 common storage allocation.
 570
 571 .TP
 572 .BI "\-Map " "mapfile"\c
 573 Print to the file
 574 .I mapfile
 575 a link map\(em\&diagnostic information
 576 about where symbols are mapped by \c
 577 .B ld\c
 578 \&, and information on global
 579 common storage allocation.
 580
 581 .TP
 582 .BI "\-m " "emulation"\c
 583 Emulate the
 584 .I emulation
 585 linker.  You can list the available emulations with the
 586 .I \-\-verbose
 587 or
 588 .I \-V
 589 options.  This option overrides the compiled-in default, which is the
 590 system for which you configured
 591 .BR ld .
 592
 593 .TP
 594 .B \-N
 595 specifies readable and writable \c
 596 .B text\c
 597 \& and \c
 598 .B data\c
 599 \& sections. If
 600 the output format supports Unix style magic numbers, the output is
 601 marked as \c
 602 .B OMAGIC\c
 603 \&.
 604
 605 When you use the `\|\c
 606 .B \-N\c
 607 \&\|' option, the linker does not page-align the
 608 data segment.
 609
 610 .TP
 611 .B \-n
 612 sets the text segment to be read only, and \c
 613 .B NMAGIC\c
 614 \& is written
 615 if possible.
 616
 617 .TP
 618 .B \-noinhibit\-exec
 619 Normally, the linker will not produce an output file if it encounters
 620 errors during the link process.  With this flag, you can specify that
 621 you wish the output file retained even after non-fatal errors.
 622
 623 .TP
 624 .B \-no\-keep\-memory
 625 The linker normally optimizes for speed over memory usage by caching
 626 the symbol tables of input files in memory.  This option tells the
 627 linker to instead optimize for memory usage, by rereading the symbol
 628 tables as necessary.  This may be required if the linker runs out of
 629 memory space while linking a large executable.
 630
 631 .TP
 632 .BI "\-o " "output"\c
 633 \&
 634 .I output\c
 635 \&
 636 \c
 637 .I output\c
 638 \& is a name for the program produced by \c
 639 .B ld\c
 640 \&; if this
 641 option is not specified, the name `\|\c
 642 .B a.out\c
 643 \|' is used by default.  The
 644 script command \c
 645 .B OUTPUT\c
 646 \& can also specify the output file name.
 647
 648 .TP
 649 .BI "\-oformat " "output\-format"\c
 650 \&
 651 Specify the binary format for the output object file.
 652 You don't usually need to specify this, as
 653 \c
 654 .B ld\c
 655 \& is configured to produce as a default output format the most
 656 usual format on each machine.  \c
 657 .I output-format\c
 658 \& is a text string, the
 659 name of a particular format supported by the BFD libraries.
 660 The script command
 661 .B OUTPUT_FORMAT
 662 can also specify the output format, but this option overrides it.
 663
 664 .TP
 665 .BI "\-R " "filename"\c
 666 \&
 667 .I file\c
 668 \&
 669 Read symbol names and their addresses from \c
 670 .I filename\c
 671 \&, but do not
 672 relocate it or include it in the output.  This allows your output file
 673 to refer symbolically to absolute locations of memory defined in other
 674 programs.
 675
 676 .TP
 677 .B \-relax
 678 An option with machine dependent effects.  Currently this option is only
 679 supported on the H8/300.
 680
 681 On some platforms, use this option to perform global optimizations that
 682 become possible when the linker resolves addressing in your program, such
 683 as relaxing address modes and synthesizing new instructions in the
 684 output object file.
 685
 686 On platforms where this is not supported, `\|\c
 687 .B \-relax\c
 688 \&\|' is accepted, but has no effect.
 689
 690 .TP
 691 .B \-r
 692 Generates relocatable output\(em\&i.e., generate an output file that can in
 693 turn serve as input to \c
 694 .B ld\c
 695 \&.  This is often called \c
 696 .I partial
 697 linking\c
 698 \&.  As a side effect, in environments that support standard Unix
 699 magic numbers, this option also sets the output file's magic number to
 700 \c
 701 .B OMAGIC\c
 702 \&.
 703 If this option is not specified, an absolute file is produced.  When
 704 linking C++ programs, this option \c
 705 .I will not\c
 706 \& resolve references to
 707 constructors; \c
 708 .B \-Ur\c
 709 \& is an alternative.
 710
 711 This option does the same as \c
 712 .B \-i\c
 713 \&.
 714
 715 .TP
 716 .B \-S
 717 Omits debugger symbol information (but not all symbols) from the output file.
 718
 719 .TP
 720 .B \-s
 721 Omits all symbol information from the output file.
 722
 723 .TP
 724 .B \-shared
 725 Create a shared library.  This is currently only supported on ELF
 726 platforms.
 727
 728 .TP
 729 .B \-sort\-common
 730 Normally, when
 731 .B ld
 732 places the global common symbols in the appropriate output sections,
 733 it sorts them by size.  First come all the one byte symbols, then all
 734 the two bytes, then all the four bytes, and then everything else.
 735 This is to prevent gaps between symbols due to
 736 alignment constraints.  This option disables that sorting.
 737
 738 .TP
 739 .B \-split\-by\-reloc\ \fIcount
 740 Trys to creates extra sections in the output file so that no single
 741 output section in the file contains more than
 742 .I count
 743 relocations.
 744 This is useful when generating huge relocatable for downloading into
 745 certain real time kernels with the COFF object file format; since COFF
 746 cannot represent more than 65535 relocations in a single section.
 747 Note that this will fail to work with object file formats which do not
 748 support arbitrary sections.  The linker will not split up individual
 749 input sections for redistribution, so if a single input section
 750 contains more than
 751 .I count
 752 relocations one output section will contain that many relocations.
 753
 754 .TP
 755 .B \-split\-by\-file
 756 Similar to
 757 .B \-split\-by\-reloc
 758 but creates a new output section for each input file.
 759
 760 .TP
 761 .BI "\-Tbss " "org"\c
 762 .TP
 763 .BI "\-Tdata " "org"\c
 764 .TP
 765 .BI "\-Ttext " "org"\c
 766 Use \c
 767 .I org\c
 768 \& as the starting address for\(em\&respectively\(em\&the
 769 \c
 770 .B bss\c
 771 \&, \c
 772 .B data\c
 773 \&, or the \c
 774 .B text\c
 775 \& segment of the output file.
 776 \c
 777 .I textorg\c
 778 \& must be a hexadecimal integer.
 779
 780 .TP
 781 .BI "\-T " "commandfile"\c
 782 \&
 783 .TP
 784 .BI "\-T" "commandfile"\c
 785 Equivalent to \c
 786 .B \-c \c
 787 .I commandfile\c
 788 \&\c
 789 \&; supported for compatibility with
 790 other tools.
 791
 792 .TP
 793 .B \-t
 794 Prints names of input files as \c
 795 .B ld\c
 796 \& processes them.
 797
 798 .TP
 799 .BI "\-u " "sym"
 800 Forces \c
 801 .I sym\c
 802 \& to be entered in the output file as an undefined symbol.
 803 This may, for example, trigger linking of additional modules from
 804 standard libraries.  \c
 805 .B \-u\c
 806 \& may be repeated with different option
 807 arguments to enter additional undefined symbols.
 808
 809 .TP
 810 .B \-Ur
 811 For anything other than C++ programs, this option is equivalent to
 812 \c
 813 .B \-r\c
 814 \&: it generates relocatable output\(em\&i.e., an output file that can in
 815 turn serve as input to \c
 816 .B ld\c
 817 \&.  When linking C++ programs, \c
 818 .B \-Ur\c
 819 \&
 820 \c
 821 .I will\c
 822 \& resolve references to constructors, unlike \c
 823 .B \-r\c
 824 \&.
 825
 826 .TP
 827 .B \-\-verbose
 828 Display the version number for \c
 829 .B ld
 830 and list the supported emulations.
 831 Display which input files can and can not be opened.
 832
 833 .TP
 834 .B \-v, \-V
 835 Display the version number for \c
 836 .B ld\c
 837 \&.
 838 The
 839 .B \-V
 840 option also lists the supported emulations.
 841
 842 .TP
 843 .B \-\-version
 844 Display the version number for \c
 845 .B ld
 846 and exit.
 847
 848 .TP
 849 .B \-warn\-common
 850 Warn when a common symbol is combined with another common symbol or with
 851 a symbol definition.  Unix linkers allow this somewhat sloppy practice,
 852 but linkers on some other operating systems do not.  This option allows
 853 you to find potential problems from combining global symbols.
 854
 855 .TP
 856 .B \-warn\-constructors
 857 Warn if any global constructors are used.  This is only useful for a
 858 few object file formats.  For formats like COFF or ELF, the linker can
 859 not detect the use of global constructors.
 860
 861 .TP
 862 .B \-warn\-once
 863 Only warn once for each undefined symbol, rather than once per module
 864 which refers to it.
 865
 866 .TP
 867 .B \-\-whole\-archive
 868 For each archive mentioned on the command line, include every object
 869 file in the archive in the link, rather than searching the archive for
 870 the required object files.  This is normally used to turn an archive
 871 file into a shared library, forcing every object to be included in the
 872 resulting shared library.
 873
 874 .TP
 875 .B \-X
 876 Delete all temporary local symbols.  For most targets, this is all local
 877 symbols whose names begin with `\|\c
 878 .B L\c
 879 \|'.
 880
 881 .TP
 882 .B \-x
 883 Delete all local symbols.
 884
 885 .PP
 886
 887 .SH ENVIRONMENT
 888 \c
 889 You can change the behavior of
 890 .B ld\c
 891 \& with the environment variable \c
 892 .B GNUTARGET\c
 893 \&.
 894
 895 \c
 896 .B GNUTARGET\c
 897 \& determines the input-file object format if you don't
 898 use \c
 899 .B \-b\c
 900 \& (or its synonym \c
 901 .B \-format\c
 902 \&).  Its value should be one
 903 of the BFD names for an input format.  If there is no
 904 \c
 905 .B GNUTARGET\c
 906 \& in the environment, \c
 907 .B ld\c
 908 \& uses the natural format
 909 of the host. If \c
 910 .B GNUTARGET\c
 911 \& is set to \c
 912 .B default\c
 913 \& then BFD attempts to discover the
 914 input format by examining binary input files; this method often
 915 succeeds, but there are potential ambiguities, since there is no method
 916 of ensuring that the magic number used to flag object-file formats is
 917 unique.  However, the configuration procedure for BFD on each system
 918 places the conventional format for that system first in the search-list,
 919 so ambiguities are resolved in favor of convention.
 920
 921 .PP
 922
 923 .SH "SEE ALSO"
 924
 925 .BR objdump ( 1 )
 926 .br
 927 .br
 928 .RB "`\|" ld "\|' and `\|" binutils "\|'"
 929 entries in
 930 .B info\c
 931 .br
 932 .I
 933 ld: the GNU linker\c
 934 , Steve Chamberlain and Roland Pesch;
 935 .I
 936 The GNU Binary Utilities\c
 937 , Roland H. Pesch.
 938
 939 .SH COPYING
 940 Copyright (c) 1991, 1992 Free Software Foundation, Inc.
 941 .PP
 942 Permission is granted to make and distribute verbatim copies of
 943 this manual provided the copyright notice and this permission notice
 944 are preserved on all copies.
 945 .PP
 946 Permission is granted to copy and distribute modified versions of this
 947 manual under the conditions for verbatim copying, provided that the
 948 entire resulting derived work is distributed under the terms of a
 949 permission notice identical to this one.
 950 .PP
 951 Permission is granted to copy and distribute translations of this
 952 manual into another language, under the above conditions for modified
 953 versions, except that this permission notice may be included in
 954 translations approved by the Free Software Foundation instead of in
 955 the original English.