| 1 | README for gdb-4.4 release |
| 2 | John Gilmore & Stu Grossman 31 Jan 1992 |
| 3 | |
| 4 | This is GDB, the GNU source-level debugger, presently running under un*x. |
| 5 | A summary of new features is in the file `WHATS.NEW'. |
| 6 | |
| 7 | |
| 8 | Unpacking and Installation -- quick overview |
| 9 | ========================== |
| 10 | |
| 11 | In this release, the GDB debugger sources, the generic GNU include |
| 12 | files, the BFD ("binary file description") library, the readline library, |
| 13 | and a miscellaneous library all have directories of their own underneath |
| 14 | the gdb-4.4 directory. The idea is that a variety of GNU tools can |
| 15 | share a common copy of these things. Configuration scripts and |
| 16 | makefiles exist to cruise up and down this directory tree and |
| 17 | automatically build all the pieces in the right order. |
| 18 | |
| 19 | When you unpack the gdb-4.4.tar.Z file, you'll get a directory called |
| 20 | `gdb-4.4', which contains: |
| 21 | |
| 22 | DOC.configure bfd/ configure* glob/ readline/ |
| 23 | Makefile.in config/ configure.in include/ texinfo/ |
| 24 | README config.sub* gdb/ libiberty/ |
| 25 | |
| 26 | To build GDB, you can just do: |
| 27 | |
| 28 | cd gdb-4.4 |
| 29 | ./configure HOSTTYPE (e.g. sun4, decstation) |
| 30 | make |
| 31 | cp gdb/gdb /usr/local/bin/gdb (or wherever you want) |
| 32 | |
| 33 | This will configure and build all the libraries as well as GDB. |
| 34 | If you get compiler warnings during this stage, see the `Reporting Bugs' |
| 35 | section below; there are a few known problems. |
| 36 | |
| 37 | GDB can be used as a cross-debugger, running on a machine of one type |
| 38 | while debugging a program running on a machine of another type. See below. |
| 39 | |
| 40 | |
| 41 | More Documentation |
| 42 | ================== |
| 43 | |
| 44 | The GDB 4 release includes an already-formatted reference card, |
| 45 | ready for printing on a PostScript or GhostScript printer, in the `gdb' |
| 46 | subdirectory of the main source directory--in `gdb-4.4/gdb/refcard.ps' |
| 47 | of the version 4.4 release. If you have a PostScript or GhostScript |
| 48 | printer, you can print the reference card by just sending `refcard.ps' |
| 49 | to the printer. |
| 50 | |
| 51 | If all you have is TeX, format the GDB reference card by typing: |
| 52 | |
| 53 | make refcard.dvi |
| 54 | |
| 55 | The GDB reference card is designed to print in landscape mode on US |
| 56 | "letter" size paper; that is, on a sheet 11 inches wide by 8.5 inches |
| 57 | high. You will need to specify this form of printing as an option to |
| 58 | your DVI output program. |
| 59 | |
| 60 | All the documentation for GDB comes as part of the online |
| 61 | distribution. The documentation is written in Texinfo format, |
| 62 | which is a documentation system that uses a single source file to |
| 63 | produce both on-line information and a printed manual. You can use |
| 64 | one of the Info formatting commands to create the on-line version of |
| 65 | the documentation and TeX (or `texi2roff') to typeset the printed |
| 66 | version. |
| 67 | |
| 68 | GDB includes an already formatted copy of the on-line Info version |
| 69 | of this manual in the `gdb' subdirectory. The main Info file is |
| 70 | `gdb-VERSION-NUMBER/gdb/gdb.info', and it refers to subordinate files |
| 71 | matching `gdb.info*' in the same directory. |
| 72 | |
| 73 | If you want to format these Info files yourself, you need one of the |
| 74 | Info formatting programs, such as `texinfo-format-buffer' or |
| 75 | `makeinfo'. |
| 76 | |
| 77 | If you have `makeinfo' installed, and are in the top level GDB |
| 78 | source directory (`gdb-4.4', in the case of version 4.4), you can make |
| 79 | the Info file by typing: |
| 80 | |
| 81 | cd gdb |
| 82 | make gdb.info |
| 83 | |
| 84 | If you want to typeset and print copies of this manual, you need |
| 85 | TeX, a printing program such as `lpr', and `texinfo.tex', the Texinfo |
| 86 | definitions file. |
| 87 | |
| 88 | TeX is typesetting program; it does not print files directly, but |
| 89 | produces output files called DVI files. To print a typeset document, |
| 90 | you need a program to print DVI files. If your system has TeX |
| 91 | installed, chances are it has such a program. The precise command to |
| 92 | use depends on your system; `lpr -d' is common; another is `dvips'. |
| 93 | The DVI print command may require a file name without any extension or |
| 94 | a `.dvi' extension. |
| 95 | |
| 96 | TeX also requires a macro definitions file called `texinfo.tex'. |
| 97 | This file tells TeX how to typeset a document written in Texinfo |
| 98 | format. On its own, TeX cannot read, much less typeset a Texinfo |
| 99 | file. `texinfo.tex' is distributed with GDB and is located in the |
| 100 | `gdb-VERSION-NUMBER/texinfo' directory. |
| 101 | |
| 102 | If you have TeX and a DVI printer program installed, you can |
| 103 | typeset and print this manual. First switch to the the `gdb' |
| 104 | subdirectory of the main source directory (for example, to |
| 105 | `gdb-4.4/gdb') and then type: |
| 106 | |
| 107 | make gdb.dvi |
| 108 | |
| 109 | Installing GDB |
| 110 | ============== |
| 111 | |
| 112 | GDB comes with a `configure' script that automates the process of |
| 113 | preparing GDB for installation; you can then use `make' to build the |
| 114 | `gdb' program. |
| 115 | |
| 116 | The GDB distribution includes all the source code you need for GDB |
| 117 | in a single directory, whose name is usually composed by appending the |
| 118 | version number to `gdb'. |
| 119 | |
| 120 | For example, the GDB version 4.4 distribution is in the `gdb-4.4' |
| 121 | directory. That directory contains: |
| 122 | |
| 123 | `gdb-4.4/configure (and supporting files)' |
| 124 | script for configuring GDB and all its supporting libraries. |
| 125 | |
| 126 | `gdb-4.4/gdb' |
| 127 | the source specific to GDB itself |
| 128 | |
| 129 | `gdb-4.4/bfd' |
| 130 | source for the Binary File Descriptor Library |
| 131 | |
| 132 | `gdb-4.4/include' |
| 133 | GNU include files |
| 134 | |
| 135 | `gdb-4.4/libiberty' |
| 136 | source for the `-liberty' free software library |
| 137 | |
| 138 | `gdb-4.4/readline' |
| 139 | source for the GNU command-line interface |
| 140 | |
| 141 | The simplest way to configure and build GDB is to run `configure' |
| 142 | from the `gdb-VERSION-NUMBER' source directory, which in this example |
| 143 | is the `gdb-4.4' directory. |
| 144 | |
| 145 | First switch to the `gdb-VERSION-NUMBER' source directory if you |
| 146 | are not already in it; then run `configure'. Pass the identifier for |
| 147 | the platform on which GDB will run as an argument. |
| 148 | |
| 149 | For example: |
| 150 | |
| 151 | cd gdb-4.4 |
| 152 | ./configure HOST |
| 153 | make |
| 154 | |
| 155 | where HOST is an identifier such as `sun4' or `decstation', that |
| 156 | identifies the platform where GDB will run. |
| 157 | |
| 158 | These `configure' and `make' commands build the three libraries `bfd', |
| 159 | `readline', and `libiberty', then `gdb' itself. The configured source |
| 160 | files, and the binaries, are left in the corresponding source |
| 161 | directories. |
| 162 | |
| 163 | `configure' is a Bourne-shell (`/bin/sh') script; if your system |
| 164 | does not recognize this automatically when you run a different shell, |
| 165 | you may need to run `sh' on it explicitly: |
| 166 | |
| 167 | sh configure HOST |
| 168 | |
| 169 | If you run `configure' from a directory that contains source |
| 170 | directories for multiple libraries or programs, such as the `gdb-4.4' |
| 171 | source directory for version 4.4, `configure' creates configuration |
| 172 | files for every directory level underneath (unless you tell it not to, |
| 173 | with the `--norecursion' option). |
| 174 | |
| 175 | You can run the `configure' script from any of the subordinate |
| 176 | directories in the GDB distribution, if you only want to configure |
| 177 | that subdirectory; but be sure to specify a path to it. |
| 178 | |
| 179 | For example, with version 4.4, type the following to configure only |
| 180 | the `bfd' subdirectory: |
| 181 | |
| 182 | cd gdb-4.4/bfd |
| 183 | ../configure HOST |
| 184 | |
| 185 | You can install `gdb' anywhere; it has no hardwired paths. |
| 186 | However, you should make sure that the shell on your path (named by |
| 187 | the `SHELL' environment variable) is publicly readable. Remember that |
| 188 | GDB uses the shell to start your program--some systems refuse to let |
| 189 | GDB debug child processes whose programs are not readable. |
| 190 | |
| 191 | |
| 192 | Compiling GDB in Another Directory |
| 193 | ================================== |
| 194 | |
| 195 | If you want to run GDB versions for several host or target machines, |
| 196 | you'll need a different `gdb' compiled for each combination of host |
| 197 | and target. `configure' is designed to make this easy by allowing you |
| 198 | to generate each configuration in a separate subdirectory, rather than |
| 199 | in the source directory. If your `make' program handles the `VPATH' |
| 200 | feature (GNU `make' does), running `make' in each of these directories |
| 201 | then builds the `gdb' program specified there. |
| 202 | |
| 203 | To build `gdb' in a separate directory, run `configure' with the |
| 204 | `--srcdir' option to specify where to find the source. (Remember, |
| 205 | you'll also need to specify a path to find `configure' itself from |
| 206 | your working directory.) |
| 207 | |
| 208 | For example, with version 4.4, you can build GDB in a separate |
| 209 | directory for a Sun 4 like this: |
| 210 | |
| 211 | cd gdb-4.4 |
| 212 | mkdir ../gdb-sun4 |
| 213 | cd ../gdb-sun4 |
| 214 | ../gdb-4.4/configure --srcdir=../gdb-4.4 sun4 |
| 215 | make |
| 216 | |
| 217 | When `configure' builds a configuration using a remote source |
| 218 | directory, it creates a tree for the binaries with the same structure |
| 219 | (and using the same names) as the tree under the source directory. In |
| 220 | the example, you'd find the Sun 4 library `libiberty.a' in the |
| 221 | directory `gdb-sun4/libiberty', and GDB itself in `gdb-sun4/gdb'. |
| 222 | |
| 223 | One popular use for building several GDB configurations in separate |
| 224 | directories is to configure GDB for cross-compiling (where GDB runs on |
| 225 | one machine--the host--while debugging programs that run on another |
| 226 | machine--the target). You specify a cross-debugging target by giving |
| 227 | the `--target=TARGET' option to `configure'. |
| 228 | |
| 229 | When you run `make' to build a program or library, you must run it |
| 230 | in a configured directory--whatever directory you were in when you |
| 231 | called `configure' (or one of its subdirectories). |
| 232 | |
| 233 | The `Makefile' generated by `configure' for each source directory |
| 234 | also runs recursively. If you type `make' in a source directory such |
| 235 | as `gdb-4.4' (or in a separate configured directory configured with |
| 236 | `--srcdir=PATH/gdb-4.4'), you will build all the required libraries, |
| 237 | then build GDB. |
| 238 | |
| 239 | When you have multiple hosts or targets configured in separate |
| 240 | directories, you can run `make' on them in parallel (for example, if |
| 241 | they are NFS-mounted on each of the hosts); they will not interfere |
| 242 | with each other. |
| 243 | |
| 244 | |
| 245 | Specifying Names for Hosts and Targets |
| 246 | ====================================== |
| 247 | |
| 248 | The specifications used for hosts and targets in the `configure' |
| 249 | script are based on a three-part naming scheme, but some short |
| 250 | predefined aliases are also supported. The full naming scheme encodes |
| 251 | three pieces of information in the following pattern: |
| 252 | |
| 253 | ARCHITECTURE-VENDOR-OS |
| 254 | |
| 255 | For example, you can use the alias `sun4' as a HOST argument or in |
| 256 | a `+target=TARGET' option, but the equivalent full name is |
| 257 | `sparc-sun-sunos4'. |
| 258 | |
| 259 | The following table shows all the architectures, hosts, and OS |
| 260 | prefixes that `configure' recognizes in GDB version 4.4. Entries in |
| 261 | the "OS prefix" column ending in a `*' may be followed by a release |
| 262 | number. |
| 263 | |
| 264 | |
| 265 | ARCHITECTURE VENDOR OS prefix |
| 266 | ------------+--------------------------+--------------------------- |
| 267 | | | |
| 268 | 580 | altos hp | aix* msdos* |
| 269 | a29k | amd ibm | amigados newsos* |
| 270 | alliant | amdahl intel | aout nindy* |
| 271 | arm | aout isi | bout osf* |
| 272 | c1 | apollo little | bsd* sco* |
| 273 | c2 | att mips | coff sunos* |
| 274 | cray2 | bcs motorola | ctix* svr4 |
| 275 | h8300 | bout ncr | dgux* sym* |
| 276 | i386 | bull next | dynix* sysv* |
| 277 | i860 | cbm nyu | ebmon ultrix* |
| 278 | i960 | coff sco | esix* unicos* |
| 279 | m68000 | convergent sequent | hds unos* |
| 280 | m68k | convex sgi | hpux* uts |
| 281 | m88k | cray sony | irix* v88r* |
| 282 | mips | dec sun | isc* vms* |
| 283 | ns32k | encore unicom | kern vxworks* |
| 284 | pyramid | gould utek | mach* |
| 285 | romp | hitachi wrs | |
| 286 | rs6000 | | |
| 287 | sparc | | |
| 288 | tahoe | | |
| 289 | tron | | |
| 290 | vax | | |
| 291 | xmp | | |
| 292 | ymp | | |
| 293 | |
| 294 | *Warning:* `configure' can represent a very large number of |
| 295 | combinations of architecture, vendor, and OS. There is by no |
| 296 | means support available for all possible combinations! |
| 297 | |
| 298 | The `configure' script accompanying GDB does not provide any query |
| 299 | facility to list all supported host and target names or aliases. |
| 300 | `configure' calls the Bourne shell script `config.sub' to map |
| 301 | abbreviations to full names; you can read the script, if you wish, or |
| 302 | you can use it to test your guesses on abbreviations--for example: |
| 303 | |
| 304 | % sh config.sub sun4 |
| 305 | sparc-sun-sunos4 |
| 306 | % sh config.sub sun3 |
| 307 | m68k-sun-sunos4 |
| 308 | % sh config.sub decstation |
| 309 | mips-dec-ultrix |
| 310 | % sh config.sub hp300bsd |
| 311 | m68k-hp-bsd |
| 312 | % sh config.sub i386v |
| 313 | i386-none-sysv |
| 314 | % sh config.sub i486v |
| 315 | *** Configuration "i486v" not recognized |
| 316 | |
| 317 | `config.sub' is also distributed in the GDB source directory |
| 318 | (`gdb-4.4', for version 4.4). |
| 319 | |
| 320 | |
| 321 | `configure' Options |
| 322 | =================== |
| 323 | |
| 324 | Here is a summary of all the `configure' options and arguments that |
| 325 | you might use for building GDB: |
| 326 | |
| 327 | configure [--destdir=DIR] [--srcdir=PATH] |
| 328 | [--norecursion] [--rm] |
| 329 | [--target=TARGET] HOST |
| 330 | |
| 331 | You may introduce options with a single `-' rather than `--' if you |
| 332 | prefer; but you may abbreviate option names if you use `--'. |
| 333 | |
| 334 | `--destdir=DIR' |
| 335 | DIR is an installation directory *path prefix*. After you |
| 336 | configure with this option, `make install' will install GDB as |
| 337 | `DIR/bin/gdb', and the libraries in `DIR/lib'. If you specify |
| 338 | `--destdir=/usr/local', for example, `make install' creates |
| 339 | `/usr/local/bin/gdb'. |
| 340 | |
| 341 | `--srcdir=PATH' |
| 342 | Use this option to make configurations in directories separate |
| 343 | from the GDB source directories. Among other things, you can use |
| 344 | this to build (or maintain) several configurations |
| 345 | simultaneously, in separate directories. `configure' writes |
| 346 | configuration specific files in the current directory, but |
| 347 | arranges for them to use the source in the directory PATH. |
| 348 | `configure' will create directories under the working directory |
| 349 | in parallel to the source directories below PATH. |
| 350 | |
| 351 | `--norecursion' |
| 352 | Configure only the directory level where `configure' is executed; |
| 353 | do not propagate configuration to subdirectories. |
| 354 | |
| 355 | `--rm' |
| 356 | Remove the configuration that the other arguments specify. |
| 357 | |
| 358 | `--target=TARGET' |
| 359 | Configure GDB for cross-debugging programs running on the |
| 360 | specified TARGET. Without this option, GDB is configured to debug |
| 361 | programs that run on the same machine (HOST) as GDB itself. |
| 362 | |
| 363 | There is no convenient way to generate a list of all available |
| 364 | targets. |
| 365 | |
| 366 | `HOST ...' |
| 367 | Configure GDB to run on the specified HOST. |
| 368 | |
| 369 | There is no convenient way to generate a list of all available |
| 370 | hosts. |
| 371 | |
| 372 | `configure' accepts other options, for compatibility with configuring |
| 373 | other GNU tools recursively; but these are the only options that |
| 374 | affect GDB or its supporting libraries. |
| 375 | |
| 376 | |
| 377 | Languages other than C |
| 378 | |
| 379 | GDB provides some support for debugging C++ progams. Partial Modula-2 |
| 380 | support is now in GDB. GDB should work with FORTRAN programs. (If you |
| 381 | have problems, please send a bug report; you may have to refer to some |
| 382 | FORTRAN variables with a trailing underscore). I am not aware of |
| 383 | anyone who is working on getting gdb to use the syntax of any other |
| 384 | language. Pascal programs which use sets, subranges, file variables, |
| 385 | or nested functions will not currently work. |
| 386 | |
| 387 | |
| 388 | Kernel debugging |
| 389 | |
| 390 | I have't done this myself so I can't really offer any advice. |
| 391 | Remote debugging over serial lines works fine, but the kernel debugging |
| 392 | code in here has not been tested in years. Van Jacobson claims to have |
| 393 | better kernel debugging. |
| 394 | |
| 395 | |
| 396 | Remote debugging |
| 397 | |
| 398 | The files m68k-stub.c and i386-stub.c contain two examples of remote |
| 399 | stubs to be used with remote.c. They are designeded to run standalone |
| 400 | on a 68k or 386 cpu and communicate properly with the remote.c stub |
| 401 | over a serial line. |
| 402 | |
| 403 | The file rem-multi.shar contains a general stub that can probably |
| 404 | run on various different flavors of unix to allow debugging over a |
| 405 | serial line from one machine to another. |
| 406 | |
| 407 | Some working remote interfaces for talking to existing ROM monitors |
| 408 | are: |
| 409 | remote-eb.c AMD 29000 "EBMON" |
| 410 | remote-nindy.c Intel 960 "Nindy" |
| 411 | remote-adapt.c AMD 29000 "Adapt" |
| 412 | remote-mm.c AMD 29000 "minimon" |
| 413 | |
| 414 | Remote-vx.c and the vx-share subdirectory contain a remote interface for the |
| 415 | VxWorks realtime kernel, which communicates over TCP using the Sun |
| 416 | RPC library. This would be a useful starting point for other remote- |
| 417 | via-ethernet back ends. |
| 418 | |
| 419 | |
| 420 | Reporting Bugs |
| 421 | |
| 422 | The correct address for reporting bugs found in gdb is |
| 423 | "bug-gdb@prep.ai.mit.edu". Please email all bugs to that address. |
| 424 | Please include the GDB version number (e.g. gdb-4.4), and how |
| 425 | you configured it (e.g. "sun4" or "mach386 host, i586-intel-synopsys |
| 426 | target"). |
| 427 | |
| 428 | A known bug: |
| 429 | |
| 430 | * If you run with a watchpoint enabled, breakpoints will become |
| 431 | erratic and might not stop the program. Disabling or deleting the |
| 432 | watchpoint will fix the problem. |
| 433 | |
| 434 | GDB can produce warnings about symbols that it does not understand. By |
| 435 | default, these warnings are disabled. You can enable them by executing |
| 436 | `set complaint 10' (which you can put in your ~/.gdbinit if you like). |
| 437 | I recommend doing this if you are working on a compiler, assembler, |
| 438 | linker, or gdb, since it will point out problems that you may be able |
| 439 | to fix. Warnings produced during symbol reading indicate some mismatch |
| 440 | between the object file and GDB's symbol reading code. In many cases, |
| 441 | it's a mismatch between the specs for the object file format, and what |
| 442 | the compiler actually outputs or the debugger actually understands. |
| 443 | |
| 444 | If you port gdb to a new machine, please send the required changes to |
| 445 | bug-gdb@prep.ai.mit.edu. There's lots of information about doing your |
| 446 | own port in the file gdb-4.4/gdb/doc/gdbint.texinfo, which you can |
| 447 | print out, or read with `info' (see the Makefile.in there). If your |
| 448 | changes are more than a few lines, obtain and send in a copyright |
| 449 | assignment from gnu@prep.ai.mit.edu, as described in the section |
| 450 | `Writing Code for GDB'. |
| 451 | |
| 452 | |
| 453 | X Windows versus GDB |
| 454 | |
| 455 | xgdb is obsolete. We are not doing any development or support of it. |
| 456 | |
| 457 | There is an "xxgdb", which shows more promise, which was posted to |
| 458 | comp.sources.x. |
| 459 | |
| 460 | For those intersted in auto display of source and the availability of |
| 461 | an editor while debugging I suggest trying gdb-mode in gnu-emacs |
| 462 | (Try typing M-x gdb RETURN). Comments on this mode are welcome. |
| 463 | |
| 464 | |
| 465 | Writing Code for GDB |
| 466 | |
| 467 | We appreciate having users contribute code that is of general use, but |
| 468 | for it to be included in future GDB releases it must be cleanly |
| 469 | written. We do not want to include changes that will needlessly make |
| 470 | future maintainance difficult. It is not much harder to do things |
| 471 | right, and in the long term it is worth it to the GNU project, and |
| 472 | probably to you individually as well. |
| 473 | |
| 474 | If you make substantial changes, you'll have to file a copyright |
| 475 | assignment with the Free Software Foundation before we can produce a |
| 476 | release that includes your changes. Send mail requesting the copyright |
| 477 | assignment to gnu@prep.ai.mit.edu. Do this early, like before the |
| 478 | changes actually work, or even before you start them, because a manager |
| 479 | or lawyer on your end will probably make this a slow process. |
| 480 | |
| 481 | Please code according to the GNU coding standards. If you do not have |
| 482 | a copy, you can request one by sending mail to gnu@prep.ai.mit.edu. |
| 483 | |
| 484 | Please try to avoid making machine-specific changes to |
| 485 | machine-independent files. If this is unavoidable, put a hook in the |
| 486 | machine-independent file which calls a (possibly) machine-dependent |
| 487 | macro (for example, the IGNORE_SYMBOL macro can be used for any |
| 488 | symbols which need to be ignored on a specific machine. Calling |
| 489 | IGNORE_SYMBOL in dbxread.c is a lot cleaner than a maze of #if |
| 490 | defined's). The machine-independent code should do whatever "most" |
| 491 | machines want if the macro is not defined in param.h. Using #if |
| 492 | defined can sometimes be OK (e.g. SET_STACK_LIMIT_HUGE) but should be |
| 493 | conditionalized on a specific feature of an operating system (set in |
| 494 | tm.h or xm.h) rather than something like #if defined(vax) or #if |
| 495 | defined(SYSV). If you use an #ifdef on some symbol that is defined |
| 496 | in a header file (e.g. #ifdef TIOCSETP), *please* make sure that you |
| 497 | have #include'd the relevant header file in that module! |
| 498 | |
| 499 | It is better to replace entire routines which may be system-specific, |
| 500 | rather than put in a whole bunch of hooks which are probably not going |
| 501 | to be helpful for any purpose other than your changes. For example, |
| 502 | if you want to modify dbxread.c to deal with DBX debugging symbols |
| 503 | which are in COFF files rather than BSD a.out files, do something |
| 504 | along the lines of a macro GET_NEXT_SYMBOL, which could have |
| 505 | different definitions for COFF and a.out, rather than trying to put |
| 506 | the necessary changes throughout all the code in dbxread.c that |
| 507 | currently assumes BSD format. |
| 508 | |
| 509 | When generalizing GDB along a particular interface, please use an |
| 510 | attribute-struct rather than inserting tests or switch statements |
| 511 | everywhere. For example, GDB has been generalized to handle multiple |
| 512 | kinds of remote interfaces -- not by #ifdef's everywhere, but by |
| 513 | defining the "target_ops" structure and having a current target (as |
| 514 | well as a stack of targets below it, for memory references). Whenever |
| 515 | something needs to be done that depends on which remote interface we |
| 516 | are using, a flag in the current target_ops structure is tested (e.g. |
| 517 | `target_has_stack'), or a function is called through a pointer in the |
| 518 | current target_ops structure. In this way, when a new remote interface |
| 519 | is added, only one module needs to be touched -- the one that actually |
| 520 | implements the new remote interface. Other examples of |
| 521 | attribute-structs are BFD access to multiple kinds of object file |
| 522 | formats, or GDB's access to multiple source languages. |
| 523 | |
| 524 | Please avoid duplicating code. For example, in GDB 3.x all the stuff |
| 525 | in infptrace.c was duplicated in *-dep.c, and so changing something |
| 526 | was very painful. In GDB 4.x, these have all been consolidated |
| 527 | into infptrace.c. infptrace.c can deal with variations between |
| 528 | systems the same way any system-independent file would (hooks, #if |
| 529 | defined, etc.), and machines which are radically different don't need |
| 530 | to use infptrace.c at all. The same was true of core_file_command |
| 531 | and exec_file_command. |
| 532 | |
| 533 | |
| 534 | Debugging gdb with itself |
| 535 | |
| 536 | If gdb is limping on your machine, this is the preferred way to get it |
| 537 | fully functional. Be warned that in some ancient Unix systems, like |
| 538 | Ultrix 4.0, a program can't be running in one process while it is being |
| 539 | debugged in another. Rather than doing "./gdb ./gdb", which works on |
| 540 | Suns and such, you can copy gdb to gdb2 and then do "./gdb ./gdb2". |
| 541 | |
| 542 | When you run gdb in the gdb source directory, it will read a ".gdbinit" |
| 543 | file that sets up some simple things to make debugging gdb easier. The |
| 544 | "info" command, when executed without a subcommand in a gdb being |
| 545 | debugged by gdb, will pop you back up to the top level gdb. See |
| 546 | .gdbinit for details. |
| 547 | |
| 548 | I strongly recommend printing out the reference card and using it. |
| 549 | Send reference-card suggestions to bug-gdb@prep.ai.mit.edu, just like bugs. |
| 550 | |
| 551 | If you use emacs, you will probably want to do a "make TAGS" after you |
| 552 | configure your distribution; this will put the machine dependent |
| 553 | routines for your local machine where they will be accessed first by a |
| 554 | M-period. |
| 555 | |
| 556 | Also, make sure that you've either compiled gdb with your local cc, or |
| 557 | have run `fixincludes' if you are compiling with gcc. |
| 558 | \f |
| 559 | (this is for editing this file with GNU emacs) |
| 560 | Local Variables: |
| 561 | mode: text |
| 562 | End: |