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INFO-DIR-SECTION Programming & development tools.
START-INFO-DIR-ENTRY
* Gdb: (gdb).                     The GNU debugger.
END-INFO-DIR-ENTRY

   This file documents the GNU debugger GDB.

   This is the Ninth Edition, December 2001, of `Debugging with GDB:
the GNU Source-Level Debugger' for GDB Version 5.3.

   Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
1998,
1999, 2000, 2001, 2002 Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software" and "Free Software Needs Free
Documentation", with the Front-Cover Texts being "A GNU Manual," and
with the Back-Cover Texts as in (a) below.

   (a) The Free Software Foundation's Back-Cover Text is: "You have
freedom to copy and modify this GNU Manual, like GNU software.  Copies
published by the Free Software Foundation raise funds for GNU
development."


File: gdb.info,  Node: ST2000,  Next: Z8000,  Prev: Sparclite,  Up: Embedded Processors

Tandem ST2000
-------------

   GDB may be used with a Tandem ST2000 phone switch, running Tandem's
STDBUG protocol.

   To connect your ST2000 to the host system, see the manufacturer's
manual.  Once the ST2000 is physically attached, you can run:

     target st2000 DEV SPEED

to establish it as your debugging environment.  DEV is normally the
name of a serial device, such as `/dev/ttya', connected to the ST2000
via a serial line.  You can instead specify DEV as a TCP connection
(for example, to a serial line attached via a terminal concentrator)
using the syntax `HOSTNAME:PORTNUMBER'.

   The `load' and `attach' commands are _not_ defined for this target;
you must load your program into the ST2000 as you normally would for
standalone operation.  GDB reads debugging information (such as
symbols) from a separate, debugging version of the program available on
your host computer.

   These auxiliary GDB commands are available to help you with the
ST2000 environment:

`st2000 COMMAND'
     Send a COMMAND to the STDBUG monitor.  See the manufacturer's
     manual for available commands.

`connect'
     Connect the controlling terminal to the STDBUG command monitor.
     When you are done interacting with STDBUG, typing either of two
     character sequences gets you back to the GDB command prompt:
     `<RET>~.' (Return, followed by tilde and period) or `<RET>~<C-d>'
     (Return, followed by tilde and control-D).


File: gdb.info,  Node: Z8000,  Prev: ST2000,  Up: Embedded Processors

Zilog Z8000
-----------

   When configured for debugging Zilog Z8000 targets, GDB includes a
Z8000 simulator.

   For the Z8000 family, `target sim' simulates either the Z8002 (the
unsegmented variant of the Z8000 architecture) or the Z8001 (the
segmented variant).  The simulator recognizes which architecture is
appropriate by inspecting the object code.

`target sim ARGS'
     Debug programs on a simulated CPU.  If the simulator supports setup
     options, specify them via ARGS.

After specifying this target, you can debug programs for the simulated
CPU in the same style as programs for your host computer; use the
`file' command to load a new program image, the `run' command to run
your program, and so on.

   As well as making available all the usual machine registers (*note
Registers: Registers.), the Z8000 simulator provides three additional
items of information as specially named registers:

`cycles'
     Counts clock-ticks in the simulator.

`insts'
     Counts instructions run in the simulator.

`time'
     Execution time in 60ths of a second.

   You can refer to these values in GDB expressions with the usual
conventions; for example, `b fputc if $cycles>5000' sets a conditional
breakpoint that suspends only after at least 5000 simulated clock ticks.


File: gdb.info,  Node: Architectures,  Prev: Embedded Processors,  Up: Configurations

Architectures
=============

   This section describes characteristics of architectures that affect
all uses of GDB with the architecture, both native and cross.

* Menu:

* A29K::
* Alpha::
* MIPS::


File: gdb.info,  Node: A29K,  Next: Alpha,  Up: Architectures

A29K
----

`set rstack_high_address ADDRESS'
     On AMD 29000 family processors, registers are saved in a separate
     "register stack".  There is no way for GDB to determine the extent
     of this stack.  Normally, GDB just assumes that the stack is
     "large enough".  This may result in GDB referencing memory
     locations that do not exist.  If necessary, you can get around
     this problem by specifying the ending address of the register
     stack with the `set rstack_high_address' command.  The argument
     should be an address, which you probably want to precede with `0x'
     to specify in hexadecimal.

`show rstack_high_address'
     Display the current limit of the register stack, on AMD 29000
     family processors.


File: gdb.info,  Node: Alpha,  Next: MIPS,  Prev: A29K,  Up: Architectures

Alpha
-----

   See the following section.


File: gdb.info,  Node: MIPS,  Prev: Alpha,  Up: Architectures

MIPS
----

   Alpha- and MIPS-based computers use an unusual stack frame, which
sometimes requires GDB to search backward in the object code to find
the beginning of a function.

   To improve response time (especially for embedded applications, where
GDB may be restricted to a slow serial line for this search) you may
want to limit the size of this search, using one of these commands:

`set heuristic-fence-post LIMIT'
     Restrict GDB to examining at most LIMIT bytes in its search for
     the beginning of a function.  A value of 0 (the default) means
     there is no limit.  However, except for 0, the larger the limit
     the more bytes `heuristic-fence-post' must search and therefore
     the longer it takes to run.

`show heuristic-fence-post'
     Display the current limit.

These commands are available _only_ when GDB is configured for
debugging programs on Alpha or MIPS processors.


File: gdb.info,  Node: Controlling GDB,  Next: Sequences,  Prev: Configurations,  Up: Top

Controlling GDB
***************

   You can alter the way GDB interacts with you by using the `set'
command.  For commands controlling how GDB displays data, see *Note
Print settings: Print Settings.  Other settings are described here.

* Menu:

* Prompt::                      Prompt
* Editing::                     Command editing
* History::                     Command history
* Screen Size::                 Screen size
* Numbers::                     Numbers
* Messages/Warnings::           Optional warnings and messages
* Debugging Output::            Optional messages about internal happenings


File: gdb.info,  Node: Prompt,  Next: Editing,  Up: Controlling GDB

Prompt
======

   GDB indicates its readiness to read a command by printing a string
called the "prompt".  This string is normally `(gdb)'.  You can change
the prompt string with the `set prompt' command.  For instance, when
debugging GDB with GDB, it is useful to change the prompt in one of the
GDB sessions so that you can always tell which one you are talking to.

   _Note:_  `set prompt' does not add a space for you after the prompt
you set.  This allows you to set a prompt which ends in a space or a
prompt that does not.

`set prompt NEWPROMPT'
     Directs GDB to use NEWPROMPT as its prompt string henceforth.

`show prompt'
     Prints a line of the form: `Gdb's prompt is: YOUR-PROMPT'


File: gdb.info,  Node: Editing,  Next: History,  Prev: Prompt,  Up: Controlling GDB

Command editing
===============

   GDB reads its input commands via the "readline" interface.  This GNU
library provides consistent behavior for programs which provide a
command line interface to the user.  Advantages are GNU Emacs-style or
"vi"-style inline editing of commands, `csh'-like history substitution,
and a storage and recall of command history across debugging sessions.

   You may control the behavior of command line editing in GDB with the
command `set'.

`set editing'
`set editing on'
     Enable command line editing (enabled by default).

`set editing off'
     Disable command line editing.

`show editing'
     Show whether command line editing is enabled.


File: gdb.info,  Node: History,  Next: Screen Size,  Prev: Editing,  Up: Controlling GDB

Command history
===============

   GDB can keep track of the commands you type during your debugging
sessions, so that you can be certain of precisely what happened.  Use
these commands to manage the GDB command history facility.

`set history filename FNAME'
     Set the name of the GDB command history file to FNAME.  This is
     the file where GDB reads an initial command history list, and
     where it writes the command history from this session when it
     exits.  You can access this list through history expansion or
     through the history command editing characters listed below.  This
     file defaults to the value of the environment variable
     `GDBHISTFILE', or to `./.gdb_history' (`./_gdb_history' on MS-DOS)
     if this variable is not set.

`set history save'
`set history save on'
     Record command history in a file, whose name may be specified with
     the `set history filename' command.  By default, this option is
     disabled.

`set history save off'
     Stop recording command history in a file.

`set history size SIZE'
     Set the number of commands which GDB keeps in its history list.
     This defaults to the value of the environment variable `HISTSIZE',
     or to 256 if this variable is not set.

   History expansion assigns special meaning to the character `!'.

   Since `!' is also the logical not operator in C, history expansion
is off by default. If you decide to enable history expansion with the
`set history expansion on' command, you may sometimes need to follow
`!' (when it is used as logical not, in an expression) with a space or
a tab to prevent it from being expanded.  The readline history
facilities do not attempt substitution on the strings `!=' and `!(',
even when history expansion is enabled.

   The commands to control history expansion are:

`set history expansion on'
`set history expansion'
     Enable history expansion.  History expansion is off by default.

`set history expansion off'
     Disable history expansion.

     The readline code comes with more complete documentation of
     editing and history expansion features.  Users unfamiliar with GNU
     Emacs or `vi' may wish to read it.

`show history'
`show history filename'
`show history save'
`show history size'
`show history expansion'
     These commands display the state of the GDB history parameters.
     `show history' by itself displays all four states.

`show commands'
     Display the last ten commands in the command history.

`show commands N'
     Print ten commands centered on command number N.

`show commands +'
     Print ten commands just after the commands last printed.


File: gdb.info,  Node: Screen Size,  Next: Numbers,  Prev: History,  Up: Controlling GDB

Screen size
===========

   Certain commands to GDB may produce large amounts of information
output to the screen.  To help you read all of it, GDB pauses and asks
you for input at the end of each page of output.  Type <RET> when you
want to continue the output, or `q' to discard the remaining output.
Also, the screen width setting determines when to wrap lines of output.
Depending on what is being printed, GDB tries to break the line at a
readable place, rather than simply letting it overflow onto the
following line.

   Normally GDB knows the size of the screen from the terminal driver
software.  For example, on Unix GDB uses the termcap data base together
with the value of the `TERM' environment variable and the `stty rows'
and `stty cols' settings.  If this is not correct, you can override it
with the `set height' and `set width' commands:

`set height LPP'
`show height'
`set width CPL'
`show width'
     These `set' commands specify a screen height of LPP lines and a
     screen width of CPL characters.  The associated `show' commands
     display the current settings.

     If you specify a height of zero lines, GDB does not pause during
     output no matter how long the output is.  This is useful if output
     is to a file or to an editor buffer.

     Likewise, you can specify `set width 0' to prevent GDB from
     wrapping its output.


File: gdb.info,  Node: Numbers,  Next: Messages/Warnings,  Prev: Screen Size,  Up: Controlling GDB

Numbers
=======

   You can always enter numbers in octal, decimal, or hexadecimal in
GDB by the usual conventions: octal numbers begin with `0', decimal
numbers end with `.', and hexadecimal numbers begin with `0x'.  Numbers
that begin with none of these are, by default, entered in base 10;
likewise, the default display for numbers--when no particular format is
specified--is base 10.  You can change the default base for both input
and output with the `set radix' command.

`set input-radix BASE'
     Set the default base for numeric input.  Supported choices for
     BASE are decimal 8, 10, or 16.  BASE must itself be specified
     either unambiguously or using the current default radix; for
     example, any of

          set radix 012
          set radix 10.
          set radix 0xa

     sets the base to decimal.  On the other hand, `set radix 10'
     leaves the radix unchanged no matter what it was.

`set output-radix BASE'
     Set the default base for numeric display.  Supported choices for
     BASE are decimal 8, 10, or 16.  BASE must itself be specified
     either unambiguously or using the current default radix.

`show input-radix'
     Display the current default base for numeric input.

`show output-radix'
     Display the current default base for numeric display.


File: gdb.info,  Node: Messages/Warnings,  Next: Debugging Output,  Prev: Numbers,  Up: Controlling GDB

Optional warnings and messages
==============================

   By default, GDB is silent about its inner workings.  If you are
running on a slow machine, you may want to use the `set verbose'
command.  This makes GDB tell you when it does a lengthy internal
operation, so you will not think it has crashed.

   Currently, the messages controlled by `set verbose' are those which
announce that the symbol table for a source file is being read; see
`symbol-file' in *Note Commands to specify files: Files.

`set verbose on'
     Enables GDB output of certain informational messages.

`set verbose off'
     Disables GDB output of certain informational messages.

`show verbose'
     Displays whether `set verbose' is on or off.

   By default, if GDB encounters bugs in the symbol table of an object
file, it is silent; but if you are debugging a compiler, you may find
this information useful (*note Errors reading symbol files: Symbol
Errors.).

`set complaints LIMIT'
     Permits GDB to output LIMIT complaints about each type of unusual
     symbols before becoming silent about the problem.  Set LIMIT to
     zero to suppress all complaints; set it to a large number to
     prevent complaints from being suppressed.

`show complaints'
     Displays how many symbol complaints GDB is permitted to produce.

   By default, GDB is cautious, and asks what sometimes seems to be a
lot of stupid questions to confirm certain commands.  For example, if
you try to run a program which is already running:

     (gdb) run
     The program being debugged has been started already.
     Start it from the beginning? (y or n)

   If you are willing to unflinchingly face the consequences of your own
commands, you can disable this "feature":

`set confirm off'
     Disables confirmation requests.

`set confirm on'
     Enables confirmation requests (the default).

`show confirm'
     Displays state of confirmation requests.


File: gdb.info,  Node: Debugging Output,  Prev: Messages/Warnings,  Up: Controlling GDB

Optional messages about internal happenings
===========================================

`set debug arch'
     Turns on or off display of gdbarch debugging info. The default is
     off

`show debug arch'
     Displays the current state of displaying gdbarch debugging info.

`set debug event'
     Turns on or off display of GDB event debugging info. The default
     is off.

`show debug event'
     Displays the current state of displaying GDB event debugging info.

`set debug expression'
     Turns on or off display of GDB expression debugging info. The
     default is off.

`show debug expression'
     Displays the current state of displaying GDB expression debugging
     info.

`set debug overload'
     Turns on or off display of GDB C++ overload debugging info. This
     includes info such as ranking of functions, etc. The default is
     off.

`show debug overload'
     Displays the current state of displaying GDB C++ overload
     debugging info.

`set debug remote'
     Turns on or off display of reports on all packets sent back and
     forth across the serial line to the remote machine.  The info is
     printed on the GDB standard output stream. The default is off.

`show debug remote'
     Displays the state of display of remote packets.

`set debug serial'
     Turns on or off display of GDB serial debugging info. The default
     is off.

`show debug serial'
     Displays the current state of displaying GDB serial debugging info.

`set debug target'
     Turns on or off display of GDB target debugging info. This info
     includes what is going on at the target level of GDB, as it
     happens. The default is off.

`show debug target'
     Displays the current state of displaying GDB target debugging info.

`set debug varobj'
     Turns on or off display of GDB variable object debugging info. The
     default is off.

`show debug varobj'
     Displays the current state of displaying GDB variable object
     debugging info.


File: gdb.info,  Node: Sequences,  Next: TUI,  Prev: Controlling GDB,  Up: Top

Canned Sequences of Commands
****************************

   Aside from breakpoint commands (*note Breakpoint command lists:
Break Commands.), GDB provides two ways to store sequences of commands
for execution as a unit: user-defined commands and command files.

* Menu:

* Define::                      User-defined commands
* Hooks::                       User-defined command hooks
* Command Files::               Command files
* Output::                      Commands for controlled output


File: gdb.info,  Node: Define,  Next: Hooks,  Up: Sequences

User-defined commands
=====================

   A "user-defined command" is a sequence of GDB commands to which you
assign a new name as a command.  This is done with the `define'
command.  User commands may accept up to 10 arguments separated by
whitespace.  Arguments are accessed within the user command via
$ARG0...$ARG9.  A trivial example:

     define adder
       print $arg0 + $arg1 + $arg2

To execute the command use:

     adder 1 2 3

This defines the command `adder', which prints the sum of its three
arguments.  Note the arguments are text substitutions, so they may
reference variables, use complex expressions, or even perform inferior
functions calls.

`define COMMANDNAME'
     Define a command named COMMANDNAME.  If there is already a command
     by that name, you are asked to confirm that you want to redefine
     it.

     The definition of the command is made up of other GDB command
     lines, which are given following the `define' command.  The end of
     these commands is marked by a line containing `end'.

`if'
     Takes a single argument, which is an expression to evaluate.  It
     is followed by a series of commands that are executed only if the
     expression is true (nonzero).  There can then optionally be a line
     `else', followed by a series of commands that are only executed if
     the expression was false.  The end of the list is marked by a line
     containing `end'.

`while'
     The syntax is similar to `if': the command takes a single argument,
     which is an expression to evaluate, and must be followed by the
     commands to execute, one per line, terminated by an `end'.  The
     commands are executed repeatedly as long as the expression
     evaluates to true.

`document COMMANDNAME'
     Document the user-defined command COMMANDNAME, so that it can be
     accessed by `help'.  The command COMMANDNAME must already be
     defined.  This command reads lines of documentation just as
     `define' reads the lines of the command definition, ending with
     `end'.  After the `document' command is finished, `help' on command
     COMMANDNAME displays the documentation you have written.

     You may use the `document' command again to change the
     documentation of a command.  Redefining the command with `define'
     does not change the documentation.

`help user-defined'
     List all user-defined commands, with the first line of the
     documentation (if any) for each.

`show user'
`show user COMMANDNAME'
     Display the GDB commands used to define COMMANDNAME (but not its
     documentation).  If no COMMANDNAME is given, display the
     definitions for all user-defined commands.

`show max-user-call-depth'
`set max-user-call-depth'
     The value of `max-user-call-depth' controls how many recursion
     levels are allowed in user-defined commands before GDB suspects an
     infinite recursion and aborts the command.

   When user-defined commands are executed, the commands of the
definition are not printed.  An error in any command stops execution of
the user-defined command.

   If used interactively, commands that would ask for confirmation
proceed without asking when used inside a user-defined command.  Many
GDB commands that normally print messages to say what they are doing
omit the messages when used in a user-defined command.


File: gdb.info,  Node: Hooks,  Next: Command Files,  Prev: Define,  Up: Sequences

User-defined command hooks
==========================

   You may define "hooks", which are a special kind of user-defined
command.  Whenever you run the command `foo', if the user-defined
command `hook-foo' exists, it is executed (with no arguments) before
that command.

   A hook may also be defined which is run after the command you
executed.  Whenever you run the command `foo', if the user-defined
command `hookpost-foo' exists, it is executed (with no arguments) after
that command.  Post-execution hooks may exist simultaneously with
pre-execution hooks, for the same command.

   It is valid for a hook to call the command which it hooks.  If this
occurs, the hook is not re-executed, thereby avoiding infinte recursion.

   In addition, a pseudo-command, `stop' exists.  Defining
(`hook-stop') makes the associated commands execute every time
execution stops in your program: before breakpoint commands are run,
displays are printed, or the stack frame is printed.

   For example, to ignore `SIGALRM' signals while single-stepping, but
treat them normally during normal execution, you could define:

     define hook-stop
     handle SIGALRM nopass
     end
     
     define hook-run
     handle SIGALRM pass
     end
     
     define hook-continue
     handle SIGLARM pass
     end

   As a further example, to hook at the begining and end of the `echo'
command, and to add extra text to the beginning and end of the message,
you could define:

     define hook-echo
     echo <<<---
     end
     
     define hookpost-echo
     echo --->>>\n
     end
     
     (gdb) echo Hello World
     <<<---Hello World--->>>
     (gdb)

   You can define a hook for any single-word command in GDB, but not
for command aliases; you should define a hook for the basic command
name, e.g.  `backtrace' rather than `bt'.  If an error occurs during
the execution of your hook, execution of GDB commands stops and GDB
issues a prompt (before the command that you actually typed had a
chance to run).

   If you try to define a hook which does not match any known command,
you get a warning from the `define' command.


File: gdb.info,  Node: Command Files,  Next: Output,  Prev: Hooks,  Up: Sequences

Command files
=============

   A command file for GDB is a file of lines that are GDB commands.
Comments (lines starting with `#') may also be included.  An empty line
in a command file does nothing; it does not mean to repeat the last
command, as it would from the terminal.

   When you start GDB, it automatically executes commands from its
"init files", normally called `.gdbinit'(1).  During startup, GDB does
the following:

  1. Reads the init file (if any) in your home directory(2).

  2. Processes command line options and operands.

  3. Reads the init file (if any) in the current working directory.

  4. Reads command files specified by the `-x' option.

   The init file in your home directory can set options (such as `set
complaints') that affect subsequent processing of command line options
and operands.  Init files are not executed if you use the `-nx' option
(*note Choosing modes: Mode Options.).

   On some configurations of GDB, the init file is known by a different
name (these are typically environments where a specialized form of GDB
may need to coexist with other forms, hence a different name for the
specialized version's init file).  These are the environments with
special init file names:

   * VxWorks (Wind River Systems real-time OS): `.vxgdbinit'

   * OS68K (Enea Data Systems real-time OS): `.os68gdbinit'

   * ES-1800 (Ericsson Telecom AB M68000 emulator): `.esgdbinit'

   You can also request the execution of a command file with the
`source' command:

`source FILENAME'
     Execute the command file FILENAME.

   The lines in a command file are executed sequentially.  They are not
printed as they are executed.  An error in any command terminates
execution of the command file and control is returned to the console.

   Commands that would ask for confirmation if used interactively
proceed without asking when used in a command file.  Many GDB commands
that normally print messages to say what they are doing omit the
messages when called from command files.

   GDB also accepts command input from standard input.  In this mode,
normal output goes to standard output and error output goes to standard
error.  Errors in a command file supplied on standard input do not
terminate execution of the command file -- execution continues with the
next command.

     gdb < cmds > log 2>&1

   (The syntax above will vary depending on the shell used.) This
example will execute commands from the file `cmds'. All output and
errors would be directed to `log'.

   ---------- Footnotes ----------

   (1) The DJGPP port of GDB uses the name `gdb.ini' instead, due to the
limitations of file names imposed by DOS filesystems.

   (2) On DOS/Windows systems, the home directory is the one pointed to
by the `HOME' environment variable.


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
     is 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 displaying a string with spaces at the
     beginning or the end, since leading and trailing spaces are
     otherwise trimmed from all arguments.  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: 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: 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 your program were to execute the C subroutine

          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: TUI,  Next: Emacs,  Prev: Sequences,  Up: Top

GDB Text User Interface
***********************

* Menu:

* TUI Overview::                TUI overview
* TUI Keys::                    TUI key bindings
* TUI Single Key Mode::         TUI single key mode
* TUI Commands::                TUI specific commands
* TUI Configuration::           TUI configuration variables

   The GDB Text User Interface, TUI in short, is a terminal interface
which uses the `curses' library to show the source file, the assembly
output, the program registers and GDB commands in separate text windows.
The TUI is available only when GDB is configured with the
`--enable-tui' configure option (*note Configure Options::).


File: gdb.info,  Node: TUI Overview,  Next: TUI Keys,  Up: TUI

TUI overview
============

   The TUI has two display modes that can be switched while GDB runs:

   * A curses (or TUI) mode in which it displays several text windows
     on the terminal.

   * A standard mode which corresponds to the GDB configured without
     the TUI.

   In the TUI mode, GDB can display several text window on the terminal:

_command_
     This window is the GDB command window with the GDB prompt and the
     GDB outputs.  The GDB input is still managed using readline but
     through the TUI.  The _command_ window is always visible.

_source_
     The source window shows the source file of the program.  The
     current line as well as active breakpoints are displayed in this
     window.

_assembly_
     The assembly window shows the disassembly output of the program.

_register_
     This window shows the processor registers.  It detects when a
     register is changed and when this is the case, registers that have
     changed are highlighted.

   The source and assembly windows show the current program position by
highlighting the current line and marking them with the `>' marker.
Breakpoints are also indicated with two markers.  A first one indicates
the breakpoint type:

`B'
     Breakpoint which was hit at least once.

`b'
     Breakpoint which was never hit.

`H'
     Hardware breakpoint which was hit at least once.

`h'
     Hardware breakpoint which was never hit.

   The second marker indicates whether the breakpoint is enabled or not:

`+'
     Breakpoint is enabled.

`-'
     Breakpoint is disabled.

   The source, assembly and register windows are attached to the thread
and the frame position.  They are updated when the current thread
changes, when the frame changes or when the program counter changes.
These three windows are arranged by the TUI according to several
layouts.  The layout defines which of these three windows are visible.
The following layouts are available:

   * source

   * assembly

   * source and assembly

   * source and registers

   * assembly and registers


   On top of the command window a status line gives various information
concerning the current process begin debugged.  The status line is
updated when the information it shows changes.  The following fields
are displayed:

_target_
     Indicates the current gdb target (*note Specifying a Debugging
     Target: Targets.).

_process_
     Gives information about the current process or thread number.
     When no process is being debugged, this field is set to `No
     process'.

_function_
     Gives the current function name for the selected frame.  The name
     is demangled if demangling is turned on (*note Print Settings::).
     When there is no symbol corresponding to the current program
     counter the string `??' is displayed.

_line_
     Indicates the current line number for the selected frame.  When
     the current line number is not known the string `??' is displayed.

_pc_
     Indicates the current program counter address.


File: gdb.info,  Node: TUI Keys,  Next: TUI Single Key Mode,  Prev: TUI Overview,  Up: TUI

TUI Key Bindings
================

   The TUI installs several key bindings in the readline keymaps (*note
Command Line Editing::).  They allow to leave or enter in the TUI mode
or they operate directly on the TUI layout and windows.  The TUI also
provides a _SingleKey_ keymap which binds several keys directly to GDB
commands.  The following key bindings are installed for both TUI mode
and the GDB standard mode.

`C-x C-a'
`C-x a'
`C-x A'
     Enter or leave the TUI mode.  When the TUI mode is left, the
     curses window management is left and GDB operates using its
     standard mode writing on the terminal directly.  When the TUI mode
     is entered, the control is given back to the curses windows.  The
     screen is then refreshed.

`C-x 1'
     Use a TUI layout with only one window.  The layout will either be
     `source' or `assembly'.  When the TUI mode is not active, it will
     switch to the TUI mode.

     Think of this key binding as the Emacs `C-x 1' binding.

`C-x 2'
     Use a TUI layout with at least two windows.  When the current
     layout shows already two windows, a next layout with two windows
     is used.  When a new layout is chosen, one window will always be
     common to the previous layout and the new one.

     Think of it as the Emacs `C-x 2' binding.

`C-x s'
     Use the TUI _SingleKey_ keymap that binds single key to gdb
     commands (*note TUI Single Key Mode::).

   The following key bindings are handled only by the TUI mode:

<PgUp>
     Scroll the active window one page up.

<PgDn>
     Scroll the active window one page down.

<Up>
     Scroll the active window one line up.

<Down>
     Scroll the active window one line down.

<Left>
     Scroll the active window one column left.

<Right>
     Scroll the active window one column right.

<C-L>
     Refresh the screen.

   In the TUI mode, the arrow keys are used by the active window for
scrolling.  This means they are not available for readline.  It is
necessary to use other readline key bindings such as <C-p>, <C-n>,
<C-b> and <C-f>.


File: gdb.info,  Node: TUI Single Key Mode,  Next: TUI Commands,  Prev: TUI Keys,  Up: TUI

TUI Single Key Mode
===================

   The TUI provides a _SingleKey_ mode in which it installs a particular
key binding in the readline keymaps to connect single keys to some gdb
commands.

`c'
     continue

`d'
     down

`f'
     finish

`n'
     next

`q'
     exit the _SingleKey_ mode.

`r'
     run

`s'
     step

`u'
     up

`v'
     info locals

`w'
     where

   Other keys temporarily switch to the GDB command prompt.  The key
that was pressed is inserted in the editing buffer so that it is
possible to type most GDB commands without interaction with the TUI
_SingleKey_ mode.  Once the command is entered the TUI _SingleKey_ mode
is restored.  The only way to permanently leave this mode is by hitting
<q> or `<C-x> <s>'.


File: gdb.info,  Node: TUI Commands,  Next: TUI Configuration,  Prev: TUI Single Key Mode,  Up: TUI

TUI specific commands
=====================

   The TUI has specific commands to control the text windows.  These
commands are always available, that is they do not depend on the
current terminal mode in which GDB runs.  When GDB is in the standard
mode, using these commands will automatically switch in the TUI mode.

`info win'
     List and give the size of all displayed windows.

`layout next'
     Display the next layout.

`layout prev'
     Display the previous layout.

`layout src'
     Display the source window only.

`layout asm'
     Display the assembly window only.

`layout split'
     Display the source and assembly window.

`layout regs'
     Display the register window together with the source or assembly
     window.

`focus next | prev | src | asm | regs | split'
     Set the focus to the named window.  This command allows to change
     the active window so that scrolling keys can be affected to
     another window.

`refresh'
     Refresh the screen.  This is similar to using <C-L> key.

`update'
     Update the source window and the current execution point.

`winheight NAME +COUNT'
`winheight NAME -COUNT'
     Change the height of the window NAME by COUNT lines.  Positive
     counts increase the height, while negative counts decrease it.


File: gdb.info,  Node: TUI Configuration,  Prev: TUI Commands,  Up: TUI

TUI configuration variables
===========================

   The TUI has several configuration variables that control the
appearance of windows on the terminal.

`set tui border-kind KIND'
     Select the border appearance for the source, assembly and register
     windows.  The possible values are the following:
    `space'
          Use a space character to draw the border.

    `ascii'
          Use ascii characters + - and | to draw the border.

    `acs'
          Use the Alternate Character Set to draw the border.  The
          border is drawn using character line graphics if the terminal
          supports them.

`set tui active-border-mode MODE'
     Select the attributes to display the border of the active window.
     The possible values are `normal', `standout', `reverse', `half',
     `half-standout', `bold' and `bold-standout'.

`set tui border-mode MODE'
     Select the attributes to display the border of other windows.  The
     MODE can be one of the following:
    `normal'
          Use normal attributes to display the border.

    `standout'
          Use standout mode.

    `reverse'
          Use reverse video mode.

    `half'
          Use half bright mode.

    `half-standout'
          Use half bright and standout mode.

    `bold'
          Use extra bright or bold mode.

    `bold-standout'
          Use extra bright or bold and standout mode.


File: gdb.info,  Node: Emacs,  Next: Annotations,  Prev: TUI,  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 screen to show both your GDB session and the source.

   Explicit GDB `list' or search commands still produce output as
usual, but you probably have no reason to use them from Emacs.

     _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 does not appear to show your source.  GDB can find programs
     by searching your environment's `PATH' variable, so the GDB input
     and output session proceeds normally; but Emacs does not 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 an absolute
     file 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 `M-:' or `ESC :', or typed in the `*scratch*' buffer, or
in your `.emacs' file) makes 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 your 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 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 &' indicates that you wish
     special formatting, and also acts 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 recreates 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 cease to
correspond properly with the code.


File: gdb.info,  Node: Annotations,  Next: GDB/MI,  Prev: Emacs,  Up: Top

GDB Annotations
***************

   This chapter describes annotations in GDB.  Annotations are designed
to interface GDB to graphical user interfaces or other similar programs
which want to interact with GDB at a relatively high level.

* Menu:

* Annotations Overview::  What annotations are; the general syntax.
* Server Prefix::       Issuing a command without affecting user state.
* Value Annotations::   Values are marked as such.
* Frame Annotations::   Stack frames are annotated.
* Displays::            GDB can be told to display something periodically.
* Prompting::           Annotations marking GDB's need for input.
* Errors::              Annotations for error messages.
* Breakpoint Info::     Information on breakpoints.
* Invalidation::        Some annotations describe things now invalid.
* Annotations for Running::
                        Whether the program is running, how it stopped, etc.
* Source Annotations::  Annotations describing source code.
* TODO::                Annotations which might be added in the future.


File: gdb.info,  Node: Annotations Overview,  Next: Server Prefix,  Up: Annotations

What is an Annotation?
======================

   To produce annotations, start GDB with the `--annotate=2' option.

   Annotations start with a newline character, two `control-z'
characters, and the name of the annotation.  If there is no additional
information associated with this annotation, the name of the annotation
is followed immediately by a newline.  If there is additional
information, the name of the annotation is followed by a space, the
additional information, and a newline.  The additional information
cannot contain newline characters.

   Any output not beginning with a newline and two `control-z'
characters denotes literal output from GDB.  Currently there is no need
for GDB to output a newline followed by two `control-z' characters, but
if there was such a need, the annotations could be extended with an
`escape' annotation which means those three characters as output.

   A simple example of starting up GDB with annotations is:

     $ gdb --annotate=2
     GNU GDB 5.0
     Copyright 2000 Free Software Foundation, Inc.
     GDB is free software, covered by the GNU General Public License,
     and you are welcome to change it and/or distribute copies of it
     under certain conditions.
     Type "show copying" to see the conditions.
     There is absolutely no warranty for GDB.  Type "show warranty"
     for details.
     This GDB was configured as "sparc-sun-sunos4.1.3"
     
     ^Z^Zpre-prompt
     (gdb)
     ^Z^Zprompt
     quit
     
     ^Z^Zpost-prompt
     $

   Here `quit' is input to GDB; the rest is output from GDB.  The three
lines beginning `^Z^Z' (where `^Z' denotes a `control-z' character) are
annotations; the rest is output from GDB.


File: gdb.info,  Node: Server Prefix,  Next: Value Annotations,  Prev: Annotations Overview,  Up: Annotations

The Server Prefix
=================

   To issue a command to GDB without affecting certain aspects of the
state which is seen by users, prefix it with `server '.  This means
that this command will not affect the command history, nor will it
affect GDB's notion of which command to repeat if <RET> is pressed on a
line by itself.

   The server prefix does not affect the recording of values into the
value history; to print a value without recording it into the value
history, use the `output' command instead of the `print' command.