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README for gdb-4.5 release Stu Grossman & John Gilmore 10 Apr 1992 This is GDB, the GNU source-level debugger, presently running under un*x. A summary of new features is in the file `WHATS.NEW'. Unpacking and Installation -- quick overview ========================== In this release, the GDB debugger sources, the generic GNU include files, the BFD ("binary file description") library, the readline library, and other libraries all have directories of their own underneath the gdb-4.5 directory. The idea is that a variety of GNU tools can share a common copy of these things. Configuration scripts and makefiles exist to cruise up and down this directory tree and automatically build all the pieces in the right order. When you unpack the gdb-4.5.tar.Z file, you'll get a directory called `gdb-4.5', which contains: Makefile.in config/ configure.man libiberty/ README config.sub* gdb/ mmalloc/ bfd/ configure* glob/ readline/ cfg-paper.texi configure.in include/ texinfo/ To build GDB, you can just do: cd gdb-4.5 ./configure HOSTTYPE (e.g. sun4, decstation) make cp gdb/gdb /usr/local/bin/gdb (or wherever you want) This will configure and build all the libraries as well as GDB. If you get compiler warnings during this stage, see the `Reporting Bugs' section below; there are a few known problems. GDB can be used as a cross-debugger, running on a machine of one type while debugging a program running on a machine of another type. See below. More Documentation ================== The GDB 4 release includes an already-formatted reference card, ready for printing on a PostScript or GhostScript printer, in the `gdb' subdirectory of the main source directory--in `gdb-4.5/gdb/refcard.ps' of the version 4.5 release. If you have a PostScript or GhostScript printer, you can print the reference card by just sending `refcard.ps' to the printer. The release also includes the source for the reference card. You can format it, using TeX, by typing: make refcard.dvi The GDB reference card is designed to print in landscape mode on US "letter" size paper; that is, on a sheet 11 inches wide by 8.5 inches high. You will need to specify this form of printing as an option to your DVI output program. All the documentation for GDB comes as part of the machine-readable distribution. The documentation is written in Texinfo format, which is a documentation system that uses a single source file to produce both on-line information and a printed manual. You can use one of the Info formatting commands to create the on-line version of the documentation and TeX (or `texi2roff') to typeset the printed version. GDB includes an already formatted copy of the on-line Info version of this manual in the `gdb' subdirectory. The main Info file is `gdb-VERSION-NUMBER/gdb/gdb.info', and it refers to subordinate files matching `gdb.info*' in the same directory. If you want to format these Info files yourself, you need one of the Info formatting programs, such as `texinfo-format-buffer' or `makeinfo'. If you have `makeinfo' installed, and are in the top level GDB source directory (`gdb-4.5', in the case of version 4.5), you can make the Info file by typing: cd gdb make gdb.info If you want to typeset and print copies of this manual, you need TeX, a printing program such as `lpr', and `texinfo.tex', the Texinfo definitions file. TeX is typesetting program; it does not print files directly, but produces output files called DVI files. To print a typeset document, you need a program to print DVI files. If your system has TeX installed, chances are it has such a program. The precise command to use depends on your system; `lpr -d' is common; another is `dvips'. The DVI print command may require a file name without any extension or a `.dvi' extension. TeX also requires a macro definitions file called `texinfo.tex'. This file tells TeX how to typeset a document written in Texinfo format. On its own, TeX cannot read, much less typeset a Texinfo file. `texinfo.tex' is distributed with GDB and is located in the `gdb-VERSION-NUMBER/texinfo' directory. If you have TeX and a DVI printer program installed, you can typeset and print this manual. First switch to the the `gdb' subdirectory of the main source directory (for example, to `gdb-4.5/gdb') and then type: make gdb.dvi Installing GDB ************** GDB comes with a `configure' script that automates the process of preparing GDB for installation; you can then use `make' to build the program. The GDB distribution includes all the source code you need for GDB in a single directory, whose name is usually composed by appending the version number to `gdb'. For example, the GDB version 4.5 distribution is in the `gdb-4.5' directory. That directory contains: `gdb-4.5/configure (and supporting files)' script for configuring GDB and all its supporting libraries. `gdb-4.5/gdb' the source specific to GDB itself `gdb-4.5/bfd' source for the Binary File Descriptor library `gdb-4.5/include' GNU include files `gdb-4.5/libiberty' source for the `-liberty' free software library `gdb-4.5/readline' source for the GNU command-line interface `gdb-4.5/glob' source for the GNU filename pattern-matching subroutine `gdb-4.5/mmalloc' source for the GNU memory-mapped malloc package The simplest way to configure and build GDB is to run `configure' from the `gdb-VERSION-NUMBER' source directory, which in this example is the `gdb-4.5' directory. First switch to the `gdb-VERSION-NUMBER' source directory if you are not already in it; then run `configure'. Pass the identifier for the platform on which GDB will run as an argument. For example: cd gdb-4.5 ./configure HOST make where HOST is an identifier such as `sun4' or `decstation', that identifies the platform where GDB will run. This sequence of `configure' and `make' builds the `bfd', `readline', `mmalloc', and `libiberty' libraries, then `gdb' itself. The configured source files, and the binaries, are left in the corresponding source directories. `configure' is a Bourne-shell (`/bin/sh') script; if your system does not recognize this automatically when you run a different shell, you may need to run `sh' on it explicitly: sh configure HOST If you run `configure' from a directory that contains source directories for multiple libraries or programs, such as the `gdb-4.5' source directory for version 4.5, `configure' creates configuration files for every directory level underneath (unless you tell it not to, with the `--norecursion' option). You can run the `configure' script from any of the subordinate directories in the GDB distribution, if you only want to configure that subdirectory; but be sure to specify a path to it. For example, with version 4.5, type the following to configure only the `bfd' subdirectory: cd gdb-4.5/bfd ../configure HOST You can install `gdb' anywhere; it has no hardwired paths. However, you should make sure that the shell on your path (named by the `SHELL' environment variable) is publicly readable. Remember that GDB uses the shell to start your program--some systems refuse to let GDB debug child processes whose programs are not readable. Compiling GDB in Another Directory ================================== If you want to run GDB versions for several host or target machines, you'll need a different `gdb' compiled for each combination of host and target. `configure' is designed to make this easy by allowing you to generate each configuration in a separate subdirectory, rather than in the source directory. If your `make' program handles the `VPATH' feature (GNU `make' does), running `make' in each of these directories then builds the `gdb' program specified there. To build `gdb' in a separate directory, run `configure' with the `--srcdir' option to specify where to find the source. (You'll also need to specify a path to find `configure' itself from your working directory. If the path to `configure' would be the same as the argument to `--srcdir', you can leave out the `--srcdir' option; it will be assumed.) For example, with version 4.5, you can build GDB in a separate directory for a Sun 4 like this: cd gdb-4.5 mkdir ../gdb-sun4 cd ../gdb-sun4 ../gdb-4.5/configure sun4 make When `configure' builds a configuration using a remote source directory, it creates a tree for the binaries with the same structure (and using the same names) as the tree under the source directory. In the example, you'd find the Sun 4 library `libiberty.a' in the directory `gdb-sun4/libiberty', and GDB itself in `gdb-sun4/gdb'. One popular use for building several GDB configurations in separate directories is to configure GDB for cross-compiling (where GDB runs on one machine--the host--while debugging programs that run on another machine--the target). You specify a cross-debugging target by giving the `--target=TARGET' option to `configure'. When you run `make' to build a program or library, you must run it in a configured directory--whatever directory you were in when you called `configure' (or one of its subdirectories). The `Makefile' generated by `configure' for each source directory also runs recursively. If you type `make' in a source directory such as `gdb-4.5' (or in a separate configured directory configured with `--srcdir=PATH/gdb-4.5'), you will build all the required libraries, then build GDB. When you have multiple hosts or targets configured in separate directories, you can run `make' on them in parallel (for example, if they are NFS-mounted on each of the hosts); they will not interfere with each other. Specifying Names for Hosts and Targets ====================================== The specifications used for hosts and targets in the `configure' script are based on a three-part naming scheme, but some short predefined aliases are also supported. The full naming scheme encodes three pieces of information in the following pattern: ARCHITECTURE-VENDOR-OS For example, you can use the alias `sun4' as a HOST argument or in a `--target=TARGET' option, but the equivalent full name is `sparc-sun-sunos4'. The following table shows all the architectures, hosts, and OS prefixes that `configure' recognizes in GDB version 4.5. Entries in the "OS prefix" column ending in a `*' may be followed by a release number. ARCHITECTURE VENDOR OS prefix ------------+--------------------------+--------------------------- | | 580 | altos hp | aix* msdos* a29k | amd ibm | amigados newsos* alliant | amdahl intel | aout nindy* arm | aout isi | bout osf* c1 | apollo little | bsd* sco* c2 | att mips | coff sunos* cray2 | bcs motorola | ctix* svr4 h8300 | bout ncr | dgux* sym* i386 | bull next | dynix* sysv* i860 | cbm nyu | ebmon ultrix* i960 | coff sco | esix* unicos* m68000 | convergent sequent | hds unos* m68k | convex sgi | hpux* uts m88k | cray sony | irix* v88r* mips | dec sun | isc* vms* ns32k | encore unicom | kern vxworks* pyramid | gould utek | mach* romp | hitachi wrs | rs6000 | | sparc | | tahoe | | tron | | vax | | xmp | | ymp | | *Warning:* `configure' can represent a very large number of combinations of architecture, vendor, and OS. There is by no means support available for all possible combinations! The `configure' script accompanying GDB does not provide any query facility to list all supported host and target names or aliases. `configure' calls the Bourne shell script `config.sub' to map abbreviations to full names; you can read the script, if you wish, or you can use it to test your guesses on abbreviations--for example: % sh config.sub sun4 sparc-sun-sunos4 % sh config.sub sun3 m68k-sun-sunos4 % sh config.sub decstation mips-dec-ultrix % sh config.sub hp300bsd m68k-hp-bsd % sh config.sub i386v i386-none-sysv % sh config.sub i786v *** Configuration "i786v" not recognized `config.sub' is also distributed in the GDB source directory (`gdb-4.5', for version 4.5). `configure' Options =================== Here is a summary of all the `configure' options and arguments that you might use for building GDB: configure [--srcdir=PATH] [--norecursion] [--rm] [--target=TARGET] HOST You may introduce options with a single `-' rather than `--' if you prefer; but you may abbreviate option names if you use `--'. `--srcdir=PATH' *Warning: using this option requires GNU `make', or another `make' that implements the `VPATH' feature.* Use this option to make configurations in directories separate from the GDB source directories. Among other things, you can use this to build (or maintain) several configurations simultaneously, in separate directories. `configure' writes configuration specific files in the current directory, but arranges for them to use the source in the directory PATH. `configure' will create directories under the working directory in parallel to the source directories below PATH. `--norecursion' Configure only the directory level where `configure' is executed; do not propagate configuration to subdirectories. `--rm' Remove the configuration that the other arguments specify. `--target=TARGET' Configure GDB for cross-debugging programs running on the specified TARGET. Without this option, GDB is configured to debug programs that run on the same machine (HOST) as GDB itself. There is no convenient way to generate a list of all available targets. `HOST ...' Configure GDB to run on the specified HOST. There is no convenient way to generate a list of all available hosts. `configure' accepts other options, for compatibility with configuring other GNU tools recursively; but these are the only options that affect GDB or its supporting libraries. Languages other than C GDB provides some support for debugging C++ progams. Partial Modula-2 support is now in GDB. GDB should work with FORTRAN programs. (If you have problems, please send a bug report; you may have to refer to some FORTRAN variables with a trailing underscore). I am not aware of anyone who is working on getting gdb to use the syntax of any other language. Pascal programs which use sets, subranges, file variables, or nested functions will not currently work. Kernel debugging I have't done this myself so I can't really offer any advice. Remote debugging over serial lines works fine, but the kernel debugging code in here has not been tested in years. Van Jacobson has better kernel debugging, but the UC lawyers won't let FSF have it. Remote debugging The files m68k-stub.c and i386-stub.c contain two examples of remote stubs to be used with remote.c. They are designeded to run standalone on a 68k or 386 cpu and communicate properly with the remote.c stub over a serial line. The file rem-multi.shar contains a general stub that can probably run on various different flavors of unix to allow debugging over a serial line from one machine to another. Some working remote interfaces for talking to existing ROM monitors are: remote-eb.c AMD 29000 "EBMON" remote-nindy.c Intel 960 "Nindy" remote-adapt.c AMD 29000 "Adapt" remote-mm.c AMD 29000 "minimon" Remote-vx.c and the vx-share subdirectory contain a remote interface for the VxWorks realtime kernel, which communicates over TCP using the Sun RPC library. This would be a useful starting point for other remote- via-ethernet back ends. Reporting Bugs The correct address for reporting bugs found in gdb is "bug-gdb@prep.ai.mit.edu". Please email all bugs to that address. Please include the GDB version number (e.g. gdb-4.5), and how you configured it (e.g. "sun4" or "mach386 host, i586-intel-synopsys target"). A known bug: * If you run with a watchpoint enabled, breakpoints will become erratic and might not stop the program. Disabling or deleting the watchpoint will fix the problem. GDB can produce warnings about symbols that it does not understand. By default, these warnings are disabled. You can enable them by executing `set complaint 10' (which you can put in your ~/.gdbinit if you like). I recommend doing this if you are working on a compiler, assembler, linker, or gdb, since it will point out problems that you may be able to fix. Warnings produced during symbol reading indicate some mismatch between the object file and GDB's symbol reading code. In many cases, it's a mismatch between the specs for the object file format, and what the compiler actually outputs or the debugger actually understands. If you port gdb to a new machine, please send the required changes to bug-gdb@prep.ai.mit.edu. There's lots of information about doing your own port in the file gdb-4.5/gdb/doc/gdbint.texinfo, which you can print out, or read with `info' (see the Makefile.in there). If your changes are more than a few lines, obtain and send in a copyright assignment from gnu@prep.ai.mit.edu, as described in the section `Writing Code for GDB'. X Windows versus GDB xgdb is obsolete. We are not doing any development or support of it. There is an "xxgdb", which shows more promise, which was posted to comp.sources.x. For those intersted in auto display of source and the availability of an editor while debugging I suggest trying gdb-mode in gnu-emacs (Try typing M-x gdb RETURN). Comments on this mode are welcome. Writing Code for GDB We appreciate having users contribute code that is of general use, but for it to be included in future GDB releases it must be cleanly written. We do not want to include changes that will needlessly make future maintainance difficult. It is not much harder to do things right, and in the long term it is worth it to the GNU project, and probably to you individually as well. If you make substantial changes, you'll have to file a copyright assignment with the Free Software Foundation before we can produce a release that includes your changes. Send mail requesting the copyright assignment to gnu@prep.ai.mit.edu. Do this early, like before the changes actually work, or even before you start them, because a manager or lawyer on your end will probably make this a slow process. Please code according to the GNU coding standards. If you do not have a copy, you can request one by sending mail to gnu@prep.ai.mit.edu. Please try to avoid making machine-specific changes to machine-independent files. If this is unavoidable, put a hook in the machine-independent file which calls a (possibly) machine-dependent macro (for example, the IGNORE_SYMBOL macro can be used for any symbols which need to be ignored on a specific machine. Calling IGNORE_SYMBOL in dbxread.c is a lot cleaner than a maze of #if defined's). The machine-independent code should do whatever "most" machines want if the macro is not defined in param.h. Using #if defined can sometimes be OK (e.g. SET_STACK_LIMIT_HUGE) but should be conditionalized on a specific feature of an operating system (set in tm.h or xm.h) rather than something like #if defined(vax) or #if defined(SYSV). If you use an #ifdef on some symbol that is defined in a header file (e.g. #ifdef TIOCSETP), *please* make sure that you have #include'd the relevant header file in that module! It is better to replace entire routines which may be system-specific, rather than put in a whole bunch of hooks which are probably not going to be helpful for any purpose other than your changes. For example, if you want to modify dbxread.c to deal with DBX debugging symbols which are in COFF files rather than BSD a.out files, do something along the lines of a macro GET_NEXT_SYMBOL, which could have different definitions for COFF and a.out, rather than trying to put the necessary changes throughout all the code in dbxread.c that currently assumes BSD format. When generalizing GDB along a particular interface, please use an attribute-struct rather than inserting tests or switch statements everywhere. For example, GDB has been generalized to handle multiple kinds of remote interfaces -- not by #ifdef's everywhere, but by defining the "target_ops" structure and having a current target (as well as a stack of targets below it, for memory references). Whenever something needs to be done that depends on which remote interface we are using, a flag in the current target_ops structure is tested (e.g. `target_has_stack'), or a function is called through a pointer in the current target_ops structure. In this way, when a new remote interface is added, only one module needs to be touched -- the one that actually implements the new remote interface. Other examples of attribute-structs are BFD access to multiple kinds of object file formats, or GDB's access to multiple source languages. Please avoid duplicating code. For example, in GDB 3.x all the stuff in infptrace.c was duplicated in *-dep.c, and so changing something was very painful. In GDB 4.x, these have all been consolidated into infptrace.c. infptrace.c can deal with variations between systems the same way any system-independent file would (hooks, #if defined, etc.), and machines which are radically different don't need to use infptrace.c at all. The same was true of core_file_command and exec_file_command. Debugging gdb with itself If gdb is limping on your machine, this is the preferred way to get it fully functional. Be warned that in some ancient Unix systems, like Ultrix 4.0, a program can't be running in one process while it is being debugged in another. Rather than doing "./gdb ./gdb", which works on Suns and such, you can copy gdb to gdb2 and then do "./gdb ./gdb2". When you run gdb in the gdb source directory, it will read a ".gdbinit" file that sets up some simple things to make debugging gdb easier. The "info" command, when executed without a subcommand in a gdb being debugged by gdb, will pop you back up to the top level gdb. See .gdbinit for details. I strongly recommend printing out the reference card and using it. Send reference-card suggestions to bug-gdb@prep.ai.mit.edu, just like bugs. If you use emacs, you will probably want to do a "make TAGS" after you configure your distribution; this will put the machine dependent routines for your local machine where they will be accessed first by a M-period. Also, make sure that you've either compiled gdb with your local cc, or have run `fixincludes' if you are compiling with gcc. (this is for editing this file with GNU emacs) Local Variables: mode: text End: