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Info file gdb.info, produced by Makeinfo, -*- Text -*- from input file gdb-all.texi. This file documents the GNU debugger GDB. Copyright (C) 1988, 1989, 1990, 1991 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English. File: gdb.info, Node: Output, Prev: Command Files, Up: Sequences Commands for Controlled Output ============================== During the execution of a command file or a user-defined command, normal GDB output is suppressed; the only output that appears is what is explicitly printed by the commands in the definition. This section describes three commands useful for generating exactly the output you want. `echo TEXT' Print TEXT. Nonprinting characters can be included in TEXT using C escape sequences, such as `\n' to print a newline. No newline will be printed unless you specify one. In addition to the standard C escape sequences, a backslash followed by a space stands for a space. This is useful for outputting a string with spaces at the beginning or the end, since leading and trailing spaces are otherwise trimmed from all arguments. Thus, to print ` and foo = ', use the command `echo \ and foo = \ '. A backslash at the end of TEXT can be used, as in C, to continue the command onto subsequent lines. For example, echo This is some text\n\ which is continued\n\ onto several lines.\n produces the same output as echo This is some text\n echo which is continued\n echo onto several lines.\n `output EXPRESSION' Print the value of EXPRESSION and nothing but that value: no newlines, no `$NN = '. The value is not entered in the value history either. *Note Expressions:: for more information on expressions. `output/FMT EXPRESSION' Print the value of EXPRESSION in format FMT. You can use the same formats as for `print'; *note Output formats::., for more information. `printf STRING, EXPRESSIONS...' Print the values of the EXPRESSIONS under the control of STRING. The EXPRESSIONS are separated by commas and may be either numbers or pointers. Their values are printed as specified by STRING, exactly as if the program were to execute printf (STRING, EXPRESSIONS...); For example, you can print two values in hex like this: printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo The only backslash-escape sequences that you can use in the format string are the simple ones that consist of backslash followed by a letter. File: gdb.info, Node: Emacs, Next: GDB Bugs, Prev: Sequences, Up: Top Using GDB under GNU Emacs ************************* A special interface allows you to use GNU Emacs to view (and edit) the source files for the program you are debugging with GDB. To use this interface, use the command `M-x gdb' in Emacs. Give the executable file you want to debug as an argument. This command starts GDB as a subprocess of Emacs, with input and output through a newly created Emacs buffer. Using GDB under Emacs is just like using GDB normally except for two things: * All "terminal" input and output goes through the Emacs buffer. This applies both to GDB commands and their output, and to the input and output done by the program you are debugging. This is useful because it means that you can copy the text of previous commands and input them again; you can even use parts of the output in this way. All the facilities of Emacs' Shell mode are available for interacting with your program. In particular, you can send signals the usual way--for example, `C-c C-c' for an interrupt, `C-c C-z' for a stop. * GDB displays source code through Emacs. Each time GDB displays a stack frame, Emacs automatically finds the source file for that frame and puts an arrow (`=>') at the left margin of the current line. Emacs uses a separate buffer for source display, and splits the window to show both your GDB session and the source. Explicit GDB `list' or search commands still produce output as usual, but you probably will have no reason to use them. *Warning:* If the directory where your program resides is not your current directory, it can be easy to confuse Emacs about the location of the source files, in which case the auxiliary display buffer will not appear to show your source. GDB can find programs by searching your environment's `PATH' variable, so the GDB input and output session will proceed normally; but Emacs doesn't get enough information back from GDB to locate the source files in this situation. To avoid this problem, either start GDB mode from the directory where your program resides, or specify a full path name when prompted for the `M-x gdb' argument. A similar confusion can result if you use the GDB `file' command to switch to debugging a program in some other location, from an existing GDB buffer in Emacs. By default, `M-x gdb' calls the program called `gdb'. If you need to call GDB by a different name (for example, if you keep several configurations around, with different names) you can set the Emacs variable `gdb-command-name'; for example, (setq gdb-command-name "mygdb") (preceded by `ESC ESC', or typed in the `*scratch*' buffer, or in your `.emacs' file) will make Emacs call the program named "`mygdb'" instead. In the GDB I/O buffer, you can use these special Emacs commands in addition to the standard Shell mode commands: `C-h m' Describe the features of Emacs' GDB Mode. `M-s' Execute to another source line, like the GDB `step' command; also update the display window to show the current file and location. `M-n' Execute to next source line in this function, skipping all function calls, like the GDB `next' command. Then update the display window to show the current file and location. `M-i' Execute one instruction, like the GDB `stepi' command; update display window accordingly. `M-x gdb-nexti' Execute to next instruction, using the GDB `nexti' command; update display window accordingly. `C-c C-f' Execute until exit from the selected stack frame, like the GDB `finish' command. `M-c' Continue execution of the program, like the GDB `continue' command. *Warning:* In Emacs v19, this command is `C-c C-p'. `M-u' Go up the number of frames indicated by the numeric argument (*note Numeric Arguments: (emacs)Arguments.), like the GDB `up' command. *Warning:* In Emacs v19, this command is `C-c C-u'. `M-d' Go down the number of frames indicated by the numeric argument, like the GDB `down' command. *Warning:* In Emacs v19, this command is `C-c C-d'. `C-x &' Read the number where the cursor is positioned, and insert it at the end of the GDB I/O buffer. For example, if you wish to disassemble code around an address that was displayed earlier, type `disassemble'; then move the cursor to the address display, and pick up the argument for `disassemble' by typing `C-x &'. You can customize this further on the fly by defining elements of the list `gdb-print-command'; once it is defined, you can format or otherwise process numbers picked up by `C-x &' before they are inserted. A numeric argument to `C-x &' will both flag that you wish special formatting, and act as an index to pick an element of the list. If the list element is a string, the number to be inserted is formatted using the Emacs function `format'; otherwise the number is passed as an argument to the corresponding list element. In any source file, the Emacs command `C-x SPC' (`gdb-break') tells GDB to set a breakpoint on the source line point is on. If you accidentally delete the source-display buffer, an easy way to get it back is to type the command `f' in the GDB buffer, to request a frame display; when you run under Emacs, this will recreate the source buffer if necessary to show you the context of the current frame. The source files displayed in Emacs are in ordinary Emacs buffers which are visiting the source files in the usual way. You can edit the files with these buffers if you wish; but keep in mind that GDB communicates with Emacs in terms of line numbers. If you add or delete lines from the text, the line numbers that GDB knows will cease to correspond properly to the code. File: gdb.info, Node: GDB Bugs, Next: Renamed Commands, Prev: Emacs, Up: Top Reporting Bugs in GDB ********************* Your bug reports play an essential role in making GDB reliable. Reporting a bug may help you by bringing a solution to your problem, or it may not. But in any case the principal function of a bug report is to help the entire community by making the next version of GDB work better. Bug reports are your contribution to the maintenance of GDB. In order for a bug report to serve its purpose, you must include the information that enables us to fix the bug. * Menu: * Bug Criteria:: Have You Found a Bug? * Bug Reporting:: How to Report Bugs File: gdb.info, Node: Bug Criteria, Next: Bug Reporting, Prev: GDB Bugs, Up: GDB Bugs Have You Found a Bug? ===================== If you are not sure whether you have found a bug, here are some guidelines: * If the debugger gets a fatal signal, for any input whatever, that is a GDB bug. Reliable debuggers never crash. * If GDB produces an error message for valid input, that is a bug. * If GDB does not produce an error message for invalid input, that is a bug. However, you should note that your idea of "invalid input" might be our idea of "an extension" or "support for traditional practice". * If you are an experienced user of debugging tools, your suggestions for improvement of GDB are welcome in any case. File: gdb.info, Node: Bug Reporting, Prev: Bug Criteria, Up: GDB Bugs How to Report Bugs ================== A number of companies and individuals offer support for GNU products. If you obtained GDB from a support organization, we recommend you contact that organization first. Contact information for many support companies and individuals is available in the file `etc/SERVICE' in the GNU Emacs distribution. In any event, we also recommend that you send bug reports for GDB to one of these addresses: bug-gdb@prep.ai.mit.edu {ucbvax|mit-eddie|uunet}!prep.ai.mit.edu!bug-gdb *Do not send bug reports to `info-gdb', or to `help-gdb', or to any newsgroups.* Most users of GDB do not want to receive bug reports. Those that do, have arranged to receive `bug-gdb'. The mailing list `bug-gdb' has a newsgroup `gnu.gdb.bug' which serves as a repeater. The mailing list and the newsgroup carry exactly the same messages. Often people think of posting bug reports to the newsgroup instead of mailing them. This appears to work, but it has one problem which can be crucial: a newsgroup posting often lacks a mail path back to the sender. Thus, if we need to ask for more information, we may be unable to reach you. For this reason, it is better to send bug reports to the mailing list. As a last resort, send bug reports on paper to: GNU Debugger Bugs Free Software Foundation 545 Tech Square Cambridge, MA 02139 The fundamental principle of reporting bugs usefully is this: *report all the facts*. If you are not sure whether to state a fact or leave it out, state it! Often people omit facts because they think they know what causes the problem and assume that some details don't matter. Thus, you might assume that the name of the variable you use in an example does not matter. Well, probably it doesn't, but one cannot be sure. Perhaps the bug is a stray memory reference which happens to fetch from the location where that name is stored in memory; perhaps, if the name were different, the contents of that location would fool the debugger into doing the right thing despite the bug. Play it safe and give a specific, complete example. That is the easiest thing for you to do, and the most helpful. Keep in mind that the purpose of a bug report is to enable us to fix the bug if it is new to us. It isn't as important what happens if the bug is already known. Therefore, always write your bug reports on the assumption that the bug has not been reported previously. Sometimes people give a few sketchy facts and ask, "Does this ring a bell?" Those bug reports are useless, and we urge everyone to *refuse to respond to them* except to chide the sender to report bugs properly. To enable us to fix the bug, you should include all these things: * The version of GDB. GDB announces it if you start with no arguments; you can also print it at any time using `show version'. Without this, we won't know whether there is any point in looking for the bug in the current version of GDB. * A complete input script, and all necessary source files, that will reproduce the bug. * What compiler (and its version) was used to compile GDB--e.g. "gcc-1.37.1". * The command arguments you gave the compiler to compile your example and observe the bug. For example, did you use `-O'? To guarantee you won't omit something important, list them all. If we were to try to guess the arguments, we would probably guess wrong and then we might not encounter the bug. * The type of machine you are using, and the operating system name and version number. * A description of what behavior you observe that you believe is incorrect. For example, "It gets a fatal signal." Of course, if the bug is that GDB gets a fatal signal, then we will certainly notice it. But if the bug is incorrect output, we might not notice unless it is glaringly wrong. We are human, after all. You might as well not give us a chance to make a mistake. Even if the problem you experience is a fatal signal, you should still say so explicitly. Suppose something strange is going on, such as, your copy of GDB is out of synch, or you have encountered a bug in the C library on your system. (This has happened!) Your copy might crash and ours would not. If you told us to expect a crash, then when ours fails to crash, we would know that the bug was not happening for us. If you had not told us to expect a crash, then we would not be able to draw any conclusion from our observations. * If you wish to suggest changes to the GDB source, send us context diffs. If you even discuss something in the GDB source, refer to it by context, not by line number. The line numbers in our development sources won't match those in your sources. Your line numbers would convey no useful information to us. Here are some things that are not necessary: * A description of the envelope of the bug. Often people who encounter a bug spend a lot of time investigating which changes to the input file will make the bug go away and which changes will not affect it. This is often time consuming and not very useful, because the way we will find the bug is by running a single example under the debugger with breakpoints, not by pure deduction from a series of examples. We recommend that you save your time for something else. Of course, if you can find a simpler example to report *instead* of the original one, that is a convenience for us. Errors in the output will be easier to spot, running under the debugger will take less time, etc. However, simplification is not vital; if you don't want to do this, report the bug anyway and send us the entire test case you used. * A patch for the bug. A patch for the bug does help us if it is a good one. But don't omit the necessary information, such as the test case, on the assumption that a patch is all we need. We might see problems with your patch and decide to fix the problem another way, or we might not understand it at all. Sometimes with a program as complicated as GDB it is very hard to construct an example that will make the program follow a certain path through the code. If you don't send us the example, we won't be able to construct one, so we won't be able to verify that the bug is fixed. And if we can't understand what bug you are trying to fix, or why your patch should be an improvement, we won't install it. A test case will help us to understand. * A guess about what the bug is or what it depends on. Such guesses are usually wrong. Even we can't guess right about such things without first using the debugger to find the facts. File: gdb.info, Node: Renamed Commands, Next: Installing GDB, Prev: GDB Bugs, Up: Top Renamed Commands **************** The following commands were renamed in GDB 4.0, in order to make the command set as a whole more consistent and easier to use and remember: OLD COMMAND NEW COMMAND --------------- ------------------------------- add-syms add-symbol-file delete environment unset environment info convenience show convenience info copying show copying info directories show directories info editing show commands info history show values info targets help target info values show values info version show version info warranty show warranty set/show addressprint set/show print address set/show array-max set/show print elements set/show arrayprint set/show print array set/show asm-demangle set/show print asm-demangle set/show caution set/show confirm set/show demangle set/show print demangle set/show history write set/show history save set/show prettyprint set/show print pretty set/show screen-height set/show height set/show screen-width set/show width set/show sevenbit-strings set/show print sevenbit-strings set/show unionprint set/show print union set/show vtblprint set/show print vtbl unset [No longer an alias for delete] File: gdb.info, Node: Installing GDB, Next: Copying, Prev: Renamed Commands, Up: Top 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 `gdb' program. The gdb distribution includes all the source code you need for gdb in a single directory `gdb-4.0'. That directory in turn contains: `gdb-4.0/configure' Overall script for configuring GDB and all its supporting libraries. `gdb-4.0/gdb' the source specific to GDB itself `gdb-4.0/bfd' source for the Binary File Descriptor Library `gdb-4.0/include' GNU include files `gdb-4.0/libiberty' source for the `-liberty' free software library `gdb-4.0/readline' source for the GNU command-line interface Each of these directories has its own `configure' script, which are used by the overall `configure' script in `gdb-4.0'. It is most convenient to run `configure' from the `gdb-4.0' directory. The simplest way to configure and build GDB is the following: cd gdb-4.0 ./configure HOST make where HOST is something like `sun4' or `decstation', that identifies the platform where GDB will run. This builds the three libraries `bfd', `readline', and `libiberty', then `gdb' itself. The configured source files, and the binaries, are left in the corresponding source directories. 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; some systems refuse to let GDB debug child processes whose programs are not readable, and GDB uses the shell to start your program. * Menu: * Subdirectories:: Configuration subdirectories * Config Names:: Specifying names for hosts and targets * configure Options:: Summary of options for configure * Formatting Manual:: How to format and print GDB documentation File: gdb.info, Node: Subdirectories, Next: Config Names, Prev: Installing GDB, Up: Installing GDB Configuration Subdirectories ============================ 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. 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. `configure' creates these subdirectories for you when you simultaneously specify several configurations; but it's a good habit even for a single configuration. You can specify the use of subdirectories using the `+subdirs' option (abbreviated `+sub'). For example, you can build GDB on a Sun 4 as follows: cd gdb-4.0 ./configure +sub sun4 cd Host-sparc-sun-sunos4/Target-sparc-sun-sunos4 make When `configure' uses subdirectories to build programs or libraries, it creates nested directories `Host-HOST/Target-TARGET'. (As you see in the example, the names used for HOST and TARGET may be expanded from your `configure' argument; *note Config Names::.). `configure' uses these two directory levels because GDB can be configured for cross-compiling: GDB can run on one machine (the host) while debugging programs that run on another machine (the target). You specify cross-debugging targets by giving the `+target=TARGET' option to `configure'. Specifying only hosts still gives you two levels of subdirectory for each host, with the same configuration suffix on both; that is, if you give any number of hosts but no targets, GDB will be configured for native debugging on each host. On the other hand, whenever you specify both hosts and targets on the same command line, `configure' creates all combinations of the hosts and targets you list. When you run `make' to build a program or library, you must run it in a configured directory. If you made a single configuration, without subdirectories, run `make' in the source directory. If you have `Host-HOST/Target-TARGET' subdirectories, run `make' in those subdirectories. Each `configure' and `Makefile' under each source directory runs recursively, so that typing `make' in `gdb-4.0' (or in a `gdb-4.0/Host-HOST/Target-TARGET' subdirectory) builds all the required libraries, then GDB. If you run `configure' from a directory (such as `gdb-4.0') that contains source directories for multiple libraries or programs, `configure' creates the `Host-HOST/Target-TARGET' subdirectories in each library or program's source directory. For example, typing: cd gdb-4.0 configure sun4 +target=vxworks960 creates the following directories: gdb-4.0/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks gdb-4.0/bfd/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks gdb-4.0/gdb/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks gdb-4.0/libiberty/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks gdb-4.0/readline/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks The `Makefile' in gdb-4.0/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks will `cd' to the appropriate lower-level directories, for example: gdb-4.0/bfd/Host-sparc-sun-sunos4/Target-i960-wrs-vxworks building each in turn. When you have multiple hosts or targets configured, 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. File: gdb.info, Node: Config Names, Next: configure Options, Prev: Subdirectories, Up: Installing GDB 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 full name of that configuration specifies that the architecture is `sparc', the vendor is `sun', and the operating system is `sunos4'. The following table shows all the architectures, hosts, and OS prefixes that `configure' recognizes in GDB 4.0. Entries in the "OS prefix" column ending in a `*' may be followed by a release number. ARCHITECTURE VENDOR OS prefix ------------+-------------+------------- | | a29k | altos | aix* alliant | aout | aout arm | apollo | bout c1 | att | bsd* c2 | bout | coff i386 | coff | ctix* i860 | convergent | dynix* i960 | convex | esix* m68000 | dec | hpux* m68k | encore | isc* m88k | gould | mach* mips | hp | newsos* ns32k | ibm | nindy* pyramid | intel | none rs6000 | isi | osf* rtpc | little | sco* sparc | mips | sunos* tahoe | motorola | sysv* tron | ncr | ultrix* vax | next | unos* | none | v88r* | sco | vms* | sequent | vxworks* | sgi | | sony | | sun | | unicom | | utek | | wrs | *Warning:* Many combinations of architecture, vendor, and OS are untested. The `configure' script accompanying GDB 4.0 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 i486v *** No vendor: configuration `i486v' not recognized File: gdb.info, Node: configure Options, Next: Formatting Manual, Prev: Config Names, Up: Installing GDB `configure' Options =================== Here is a summary of all the `configure' options and arguments that you might use for building GDB: configure [+destdir=DIR] [+subdirs] [+norecur] [+rm] [+target=TARGET...] HOST... You may introduce options with the character `-' rather than `+' if you prefer; but you may abbreviate option names if you use `+'. `+destdir=DIR' DIR is an installation directory *path prefix*. After you configure with this option, `make install' will install GDB as `DIR/bin/gdb', and the libraries in `DIR/lib'. If you specify `+destdir=/usr/local', for example, `make install' creates `/usr/local/bin/gdb'. `+subdirs' Write configuration specific files in subdirectories of the form Host-HOST/Target-TARGET (and configure the `Makefile' to write binaries there too). Without this option, if you specify only one configuration for GDB, `configure' will use the same directory for source, configured files, and binaries. This option is used automatically if you specify more than one HOST or more than one `+target=TARGET' option on the `configure' command line. `+norecur' Configure only the directory 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 each specified TARGET. You may specify as many `+target' options as you wish. 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 each specified HOST. You may specify as many host names as you wish. 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. File: gdb.info, Node: Formatting Manual, Prev: configure Options, Up: Installing GDB Formatting this Manual ====================== The GDB 4.0 release includes the Info version of this manual already formatted: the main Info file is `gdb-4.0/gdb/gdb.info', and it refers to subordinate files matching `gdb.info*' in the same directory. If you want to make these Info files yourself from the GDB manual's source, you need the GNU `makeinfo' program. Once you have it, you can type cd gdb-4.0/gdb make gdb.info to make the Info file. If you want to format and print copies of this manual, you need several things: * TeX, the public domain typesetting program written by Donald Knuth, must be installed on your system and available through your execution path. * `gdb-4.0/texinfo': TeX macros defining the GNU Documentation Format. * *A DVI output program.* TeX doesn't actually make marks on paper; it produces output files called DVI files. If your system has TeX installed, chances are it has a program for printing out these files; one popular example is `dvips', which can print DVI files on PostScript printers. Once you have these things, you can type cd gdb-4.0/gdb make gdb.dvi to format the text of this manual, and print it with the usual output method for TeX DVI files at your site. You might also want hard copy of the GDB reference card. The GDB 4.0 release includes an already-formatted reference card, ready for printing on a PostScript printer, as `gdb-4.0/gdb/refcard.ps'. It uses the most common PostScript fonts: the Times family, Courier, and Symbol. If you have a PostScript printer you can print the reference card by just sending `refcard.ps' to the printer. If you have some other kind of printer, or want to print using Computer Modern fonts instead, you can still print the reference card if you have TeX. Format the reference card by typing cd gdb-4.0/gdb 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.