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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, April 2001, of `Debugging with GDB: the
GNU Source-Level Debugger' for GDB Version 20010707.

   Copyright (C)
1988,1989,1990,1991,1992,1993,1994,1995,1996,1998,1999,2000,2001
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 "A Sample GDB Session" and "Free Software",
with the Front-Cover texts being "A GNU Manual," and with the
Back-Cover Texts as in (a) below.

   (a) The FSF'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: 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.

   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".  These are files named `.gdbinit' on Unix and `gdb.ini'
on DOS/Windows.  During startup, GDB does the following:

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

  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.

   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.

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

   (1) 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: Emacs,  Next: Annotations,  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 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.


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

Values
======

   When a value is printed in various contexts, GDB uses annotations to
delimit the value from the surrounding text.

   If a value is printed using `print' and added to the value history,
the annotation looks like

     ^Z^Zvalue-history-begin HISTORY-NUMBER VALUE-FLAGS
     HISTORY-STRING
     ^Z^Zvalue-history-value
     THE-VALUE
     ^Z^Zvalue-history-end

where HISTORY-NUMBER is the number it is getting in the value history,
HISTORY-STRING is a string, such as `$5 = ', which introduces the value
to the user, THE-VALUE is the output corresponding to the value itself,
and VALUE-FLAGS is `*' for a value which can be dereferenced and `-'
for a value which cannot.

   If the value is not added to the value history (it is an invalid
float or it is printed with the `output' command), the annotation is
similar:

     ^Z^Zvalue-begin VALUE-FLAGS
     THE-VALUE
     ^Z^Zvalue-end

   When GDB prints an argument to a function (for example, in the output
from the `backtrace' command), it annotates it as follows:

     ^Z^Zarg-begin
     ARGUMENT-NAME
     ^Z^Zarg-name-end
     SEPARATOR-STRING
     ^Z^Zarg-value VALUE-FLAGS
     THE-VALUE
     ^Z^Zarg-end

where ARGUMENT-NAME is the name of the argument, SEPARATOR-STRING is
text which separates the name from the value for the user's benefit
(such as `='), and VALUE-FLAGS and THE-VALUE have the same meanings as
in a `value-history-begin' annotation.

   When printing a structure, GDB annotates it as follows:

     ^Z^Zfield-begin VALUE-FLAGS
     FIELD-NAME
     ^Z^Zfield-name-end
     SEPARATOR-STRING
     ^Z^Zfield-value
     THE-VALUE
     ^Z^Zfield-end

where FIELD-NAME is the name of the field, SEPARATOR-STRING is text
which separates the name from the value for the user's benefit (such as
`='), and VALUE-FLAGS and THE-VALUE have the same meanings as in a
`value-history-begin' annotation.

   When printing an array, GDB annotates it as follows:

     ^Z^Zarray-section-begin ARRAY-INDEX VALUE-FLAGS

where ARRAY-INDEX is the index of the first element being annotated and
VALUE-FLAGS has the same meaning as in a `value-history-begin'
annotation.  This is followed by any number of elements, where is
element can be either a single element:

     `,' WHITESPACE         ; omitted for the first element
     THE-VALUE
     ^Z^Zelt

   or a repeated element

     `,' WHITESPACE         ; omitted for the first element
     THE-VALUE
     ^Z^Zelt-rep NUMBER-OF-REPITITIONS
     REPETITION-STRING
     ^Z^Zelt-rep-end

   In both cases, THE-VALUE is the output for the value of the element
and WHITESPACE can contain spaces, tabs, and newlines.  In the repeated
case, NUMBER-OF-REPITITONS is the number of consecutive array elements
which contain that value, and REPETITION-STRING is a string which is
designed to convey to the user that repitition is being depicted.

   Once all the array elements have been output, the array annotation is
ended with

     ^Z^Zarray-section-end


File: gdb.info,  Node: Frame Annotations,  Next: Displays,  Prev: Value Annotations,  Up: Annotations

Frames
======

   Whenever GDB prints a frame, it annotates it.  For example, this
applies to frames printed when GDB stops, output from commands such as
`backtrace' or `up', etc.

   The frame annotation begins with

     ^Z^Zframe-begin LEVEL ADDRESS
     LEVEL-STRING

where LEVEL is the number of the frame (0 is the innermost frame, and
other frames have positive numbers), ADDRESS is the address of the code
executing in that frame, and LEVEL-STRING is a string designed to
convey the level to the user.  ADDRESS is in the form `0x' followed by
one or more lowercase hex digits (note that this does not depend on the
language).  The frame ends with

     ^Z^Zframe-end

   Between these annotations is the main body of the frame, which can
consist of

   *      ^Z^Zfunction-call
          FUNCTION-CALL-STRING

     where FUNCTION-CALL-STRING is text designed to convey to the user
     that this frame is associated with a function call made by GDB to a
     function in the program being debugged.

   *      ^Z^Zsignal-handler-caller
          SIGNAL-HANDLER-CALLER-STRING

     where SIGNAL-HANDLER-CALLER-STRING is text designed to convey to
     the user that this frame is associated with whatever mechanism is
     used by this operating system to call a signal handler (it is the
     frame which calls the signal handler, not the frame for the signal
     handler itself).

   * A normal frame.

     This can optionally (depending on whether this is thought of as
     interesting information for the user to see) begin with

          ^Z^Zframe-address
          ADDRESS
          ^Z^Zframe-address-end
          SEPARATOR-STRING

     where ADDRESS is the address executing in the frame (the same
     address as in the `frame-begin' annotation, but printed in a form
     which is intended for user consumption--in particular, the syntax
     varies depending on the language), and SEPARATOR-STRING is a string
     intended to separate this address from what follows for the user's
     benefit.

     Then comes

          ^Z^Zframe-function-name
          FUNCTION-NAME
          ^Z^Zframe-args
          ARGUMENTS

     where FUNCTION-NAME is the name of the function executing in the
     frame, or `??' if not known, and ARGUMENTS are the arguments to
     the frame, with parentheses around them (each argument is annotated
     individually as well, *note Value Annotations::).

     If source information is available, a reference to it is then
     printed:

          ^Z^Zframe-source-begin
          SOURCE-INTRO-STRING
          ^Z^Zframe-source-file
          FILENAME
          ^Z^Zframe-source-file-end
          :
          ^Z^Zframe-source-line
          LINE-NUMBER
          ^Z^Zframe-source-end

     where SOURCE-INTRO-STRING separates for the user's benefit the
     reference from the text which precedes it, FILENAME is the name of
     the source file, and LINE-NUMBER is the line number within that
     file (the first line is line 1).

     If GDB prints some information about where the frame is from (which
     library, which load segment, etc.; currently only done on the
     RS/6000), it is annotated with

          ^Z^Zframe-where
          INFORMATION

     Then, if source is to actually be displayed for this frame (for
     example, this is not true for output from the `backtrace'
     command), then a `source' annotation (*note Source Annotations::)
     is displayed.  Unlike most annotations, this is output instead of
     the normal text which would be output, not in addition.


File: gdb.info,  Node: Displays,  Next: Prompting,  Prev: Frame Annotations,  Up: Annotations

Displays
========

   When GDB is told to display something using the `display' command,
the results of the display are annotated:

     ^Z^Zdisplay-begin
     NUMBER
     ^Z^Zdisplay-number-end
     NUMBER-SEPARATOR
     ^Z^Zdisplay-format
     FORMAT
     ^Z^Zdisplay-expression
     EXPRESSION
     ^Z^Zdisplay-expression-end
     EXPRESSION-SEPARATOR
     ^Z^Zdisplay-value
     VALUE
     ^Z^Zdisplay-end

where NUMBER is the number of the display, NUMBER-SEPARATOR is intended
to separate the number from what follows for the user, FORMAT includes
information such as the size, format, or other information about how
the value is being displayed, EXPRESSION is the expression being
displayed, EXPRESSION-SEPARATOR is intended to separate the expression
from the text that follows for the user, and VALUE is the actual value
being displayed.


File: gdb.info,  Node: Prompting,  Next: Errors,  Prev: Displays,  Up: Annotations

Annotation for GDB Input
========================

   When GDB prompts for input, it annotates this fact so it is possible
to know when to send output, when the output from a given command is
over, etc.

   Different kinds of input each have a different "input type".  Each
input type has three annotations: a `pre-' annotation, which denotes
the beginning of any prompt which is being output, a plain annotation,
which denotes the end of the prompt, and then a `post-' annotation
which denotes the end of any echo which may (or may not) be associated
with the input.  For example, the `prompt' input type features the
following annotations:

     ^Z^Zpre-prompt
     ^Z^Zprompt
     ^Z^Zpost-prompt

   The input types are

`prompt'
     When GDB is prompting for a command (the main GDB prompt).

`commands'
     When GDB prompts for a set of commands, like in the `commands'
     command.  The annotations are repeated for each command which is
     input.

`overload-choice'
     When GDB wants the user to select between various overloaded
     functions.

`query'
     When GDB wants the user to confirm a potentially dangerous
     operation.

`prompt-for-continue'
     When GDB is asking the user to press return to continue.  Note:
     Don't expect this to work well; instead use `set height 0' to
     disable prompting.  This is because the counting of lines is buggy
     in the presence of annotations.


File: gdb.info,  Node: Errors,  Next: Breakpoint Info,  Prev: Prompting,  Up: Annotations

Errors
======

     ^Z^Zquit

   This annotation occurs right before GDB responds to an interrupt.

     ^Z^Zerror

   This annotation occurs right before GDB responds to an error.

   Quit and error annotations indicate that any annotations which GDB
was in the middle of may end abruptly.  For example, if a
`value-history-begin' annotation is followed by a `error', one cannot
expect to receive the matching `value-history-end'.  One cannot expect
not to receive it either, however; an error annotation does not
necessarily mean that GDB is immediately returning all the way to the
top level.

   A quit or error annotation may be preceded by

     ^Z^Zerror-begin

   Any output between that and the quit or error annotation is the error
message.

   Warning messages are not yet annotated.


File: gdb.info,  Node: Breakpoint Info,  Next: Invalidation,  Prev: Errors,  Up: Annotations

Information on Breakpoints
==========================

   The output from the `info breakpoints' command is annotated as
follows:

     ^Z^Zbreakpoints-headers
     HEADER-ENTRY
     ^Z^Zbreakpoints-table

where HEADER-ENTRY has the same syntax as an entry (see below) but
instead of containing data, it contains strings which are intended to
convey the meaning of each field to the user.  This is followed by any
number of entries.  If a field does not apply for this entry, it is
omitted.  Fields may contain trailing whitespace.  Each entry consists
of:

     ^Z^Zrecord
     ^Z^Zfield 0
     NUMBER
     ^Z^Zfield 1
     TYPE
     ^Z^Zfield 2
     DISPOSITION
     ^Z^Zfield 3
     ENABLE
     ^Z^Zfield 4
     ADDRESS
     ^Z^Zfield 5
     WHAT
     ^Z^Zfield 6
     FRAME
     ^Z^Zfield 7
     CONDITION
     ^Z^Zfield 8
     IGNORE-COUNT
     ^Z^Zfield 9
     COMMANDS

   Note that ADDRESS is intended for user consumption--the syntax
varies depending on the language.

   The output ends with

     ^Z^Zbreakpoints-table-end


File: gdb.info,  Node: Invalidation,  Next: Annotations for Running,  Prev: Breakpoint Info,  Up: Annotations

Invalidation Notices
====================

   The following annotations say that certain pieces of state may have
changed.

`^Z^Zframes-invalid'
     The frames (for example, output from the `backtrace' command) may
     have changed.

`^Z^Zbreakpoints-invalid'
     The breakpoints may have changed.  For example, the user just
     added or deleted a breakpoint.


File: gdb.info,  Node: Annotations for Running,  Next: Source Annotations,  Prev: Invalidation,  Up: Annotations

Running the Program
===================

   When the program starts executing due to a GDB command such as
`step' or `continue',

     ^Z^Zstarting

   is output.  When the program stops,

     ^Z^Zstopped

   is output.  Before the `stopped' annotation, a variety of
annotations describe how the program stopped.

`^Z^Zexited EXIT-STATUS'
     The program exited, and EXIT-STATUS is the exit status (zero for
     successful exit, otherwise nonzero).

`^Z^Zsignalled'
     The program exited with a signal.  After the `^Z^Zsignalled', the
     annotation continues:

          INTRO-TEXT
          ^Z^Zsignal-name
          NAME
          ^Z^Zsignal-name-end
          MIDDLE-TEXT
          ^Z^Zsignal-string
          STRING
          ^Z^Zsignal-string-end
          END-TEXT

     where NAME is the name of the signal, such as `SIGILL' or
     `SIGSEGV', and STRING is the explanation of the signal, such as
     `Illegal Instruction' or `Segmentation fault'.  INTRO-TEXT,
     MIDDLE-TEXT, and END-TEXT are for the user's benefit and have no
     particular format.

`^Z^Zsignal'
     The syntax of this annotation is just like `signalled', but GDB is
     just saying that the program received the signal, not that it was
     terminated with it.

`^Z^Zbreakpoint NUMBER'
     The program hit breakpoint number NUMBER.

`^Z^Zwatchpoint NUMBER'
     The program hit watchpoint number NUMBER.


File: gdb.info,  Node: Source Annotations,  Next: TODO,  Prev: Annotations for Running,  Up: Annotations

Displaying Source
=================

   The following annotation is used instead of displaying source code:

     ^Z^Zsource FILENAME:LINE:CHARACTER:MIDDLE:ADDR

   where FILENAME is an absolute file name indicating which source
file, LINE is the line number within that file (where 1 is the first
line in the file), CHARACTER is the character position within the file
(where 0 is the first character in the file) (for most debug formats
this will necessarily point to the beginning of a line), MIDDLE is
`middle' if ADDR is in the middle of the line, or `beg' if ADDR is at
the beginning of the line, and ADDR is the address in the target
program associated with the source which is being displayed.  ADDR is
in the form `0x' followed by one or more lowercase hex digits (note
that this does not depend on the language).


File: gdb.info,  Node: TODO,  Prev: Source Annotations,  Up: Annotations

Annotations We Might Want in the Future
=======================================

    - target-invalid
      the target might have changed (registers, heap contents, or
      execution status).  For performance, we might eventually want
      to hit `registers-invalid' and `all-registers-invalid' with
      greater precision

    - systematic annotation for set/show parameters (including
      invalidation notices).

    - similarly, `info' returns a list of candidates for invalidation
      notices.


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

The GDB/MI Interface
********************

Function and Purpose
====================

   GDB/MI is a line based machine oriented text interface to GDB.  It is
specifically intended to support the development of systems which use
the debugger as just one small component of a larger system.

   This chapter is a specification of the GDB/MI interface.  It is
written in the form of a reference manual.

   Note that GDB/MI is still under construction, so some of the
features described below are incomplete and subject to change.

Notation and Terminology
========================

   This chapter uses the following notation:

   * `|' separates two alternatives.

   * `[ SOMETHING ]' indicates that SOMETHING is optional: it may or
     may not be given.

   * `( GROUP )*' means that GROUP inside the parentheses may repeat
     zero or more times.

   * `( GROUP )+' means that GROUP inside the parentheses may repeat
     one or more times.

   * `"STRING"' means a literal STRING.

Acknowledgments
===============

   In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
Elena Zannoni.

* Menu:

* GDB/MI Command Syntax::
* GDB/MI Compatibility with CLI::
* GDB/MI Output Records::
* GDB/MI Command Description Format::
* GDB/MI Breakpoint Table Commands::
* GDB/MI Data Manipulation::
* GDB/MI Program Control::
* GDB/MI Miscellaneous Commands::
* GDB/MI Stack Manipulation::
* GDB/MI Symbol Query::
* GDB/MI Target Manipulation::
* GDB/MI Thread Commands::
* GDB/MI Tracepoint Commands::
* GDB/MI Variable Objects::


File: gdb.info,  Node: GDB/MI Command Syntax,  Next: GDB/MI Compatibility with CLI,  Up: GDB/MI

GDB/MI Command Syntax
=====================

* Menu:

* GDB/MI Input Syntax::
* GDB/MI Output Syntax::
* GDB/MI Simple Examples::


File: gdb.info,  Node: GDB/MI Input Syntax,  Next: GDB/MI Output Syntax,  Up: GDB/MI Command Syntax

GDB/MI Input Syntax
-------------------

`COMMAND ==>'
     `CLI-COMMAND | MI-COMMAND'

`CLI-COMMAND ==>'
     `[ TOKEN ] CLI-COMMAND NL', where CLI-COMMAND is any existing GDB
     CLI command.

`MI-COMMAND ==>'
     `[ TOKEN ] "-" OPERATION ( " " OPTION )* `[' " --" `]' ( " "
     PARAMETER )* NL'

`TOKEN ==>'
     "any sequence of digits"

`OPTION ==>'
     `"-" PARAMETER [ " " PARAMETER ]'

`PARAMETER ==>'
     `NON-BLANK-SEQUENCE | C-STRING'

`OPERATION ==>'
     _any of the operations described in this chapter_

`NON-BLANK-SEQUENCE ==>'
     _anything, provided it doesn't contain special characters such as
     "-", NL, """ and of course " "_

`C-STRING ==>'
     `""" SEVEN-BIT-ISO-C-STRING-CONTENT """'

`NL ==>'
     `CR | CR-LF'

Notes:

   * The CLI commands are still handled by the MI interpreter; their
     output is described below.

   * The `TOKEN', when present, is passed back when the command
     finishes.

   * Some MI commands accept optional arguments as part of the parameter
     list.  Each option is identified by a leading `-' (dash) and may be
     followed by an optional argument parameter.  Options occur first
     in the parameter list and can be delimited from normal parameters
     using `--' (this is useful when some parameters begin with a dash).

   Pragmatics:

   * We want easy access to the existing CLI syntax (for debugging).

   * We want it to be easy to spot a MI operation.


File: gdb.info,  Node: GDB/MI Output Syntax,  Next: GDB/MI Simple Examples,  Prev: GDB/MI Input Syntax,  Up: GDB/MI Command Syntax

GDB/MI Output Syntax
--------------------

   The output from GDB/MI consists of zero or more out-of-band records
followed, optionally, by a single result record.  This result record is
for the most recent command.  The sequence of output records is
terminated by `(gdb)'.

   If an input command was prefixed with a `TOKEN' then the
corresponding output for that command will also be prefixed by that same
TOKEN.

`OUTPUT ==>'
     `( OUT-OF-BAND-RECORD )* [ RESULT-RECORD ] "(gdb)" NL'

`RESULT-RECORD ==>'
     ` [ TOKEN ] "^" RESULT-CLASS ( "," RESULT )* NL'

`OUT-OF-BAND-RECORD ==>'
     `ASYNC-RECORD | STREAM-RECORD'

`ASYNC-RECORD ==>'
     `EXEC-ASYNC-OUTPUT | STATUS-ASYNC-OUTPUT | NOTIFY-ASYNC-OUTPUT'

`EXEC-ASYNC-OUTPUT ==>'
     `[ TOKEN ] "*" ASYNC-OUTPUT'

`STATUS-ASYNC-OUTPUT ==>'
     `[ TOKEN ] "+" ASYNC-OUTPUT'

`NOTIFY-ASYNC-OUTPUT ==>'
     `[ TOKEN ] "=" ASYNC-OUTPUT'

`ASYNC-OUTPUT ==>'
     `ASYNC-CLASS ( "," RESULT )* NL'

`RESULT-CLASS ==>'
     `"done" | "running" | "connected" | "error" | "exit"'

`ASYNC-CLASS ==>'
     `"stopped" | OTHERS' (where OTHERS will be added depending on the
     needs--this is still in development).

`RESULT ==>'
     ` VARIABLE "=" VALUE'

`VARIABLE ==>'
     ` STRING '

`VALUE ==>'
     ` CONST | TUPLE | LIST '

`CONST ==>'
     `C-STRING'

`TUPLE ==>'
     ` "{}" | "{" RESULT ( "," RESULT )* "}" '

`LIST ==>'
     ` "[]" | "[" VALUE ( "," VALUE )* "]" | "[" RESULT ( "," RESULT )*
     "]" '

`STREAM-RECORD ==>'
     `CONSOLE-STREAM-OUTPUT | TARGET-STREAM-OUTPUT | LOG-STREAM-OUTPUT'

`CONSOLE-STREAM-OUTPUT ==>'
     `"~" C-STRING'

`TARGET-STREAM-OUTPUT ==>'
     `"@" C-STRING'

`LOG-STREAM-OUTPUT ==>'
     `"&" C-STRING'

`NL ==>'
     `CR | CR-LF'

`TOKEN ==>'
     _any sequence of digits_.

Notes:

   * All output sequences end in a single line containing a period.

   * The `TOKEN' is from the corresponding request.  If an execution
     command is interrupted by the `-exec-interrupt' command, the TOKEN
     associated with the `*stopped' message is the one of the original
     execution command, not the one of the interrupt command.

   * STATUS-ASYNC-OUTPUT contains on-going status information about the
     progress of a slow operation.  It can be discarded.  All status
     output is prefixed by `+'.

   * EXEC-ASYNC-OUTPUT contains asynchronous state change on the target
     (stopped, started, disappeared).  All async output is prefixed by
     `*'.

   * NOTIFY-ASYNC-OUTPUT contains supplementary information that the
     client should handle (e.g., a new breakpoint information).  All
     notify output is prefixed by `='.

   * CONSOLE-STREAM-OUTPUT is output that should be displayed as is in
     the console.  It is the textual response to a CLI command.  All
     the console output is prefixed by `~'.

   * TARGET-STREAM-OUTPUT is the output produced by the target program.
     All the target output is prefixed by `@'.

   * LOG-STREAM-OUTPUT is output text coming from GDB's internals, for
     instance messages that should be displayed as part of an error
     log.  All the log output is prefixed by `&'.

   * New GDB/MI commands should only output LISTS containing VALUES.


   *Note GDB/MI Stream Records: GDB/MI Stream Records, for more details
about the various output records.


File: gdb.info,  Node: GDB/MI Simple Examples,  Prev: GDB/MI Output Syntax,  Up: GDB/MI Command Syntax

Simple Examples of GDB/MI Interaction
-------------------------------------

   This subsection presents several simple examples of interaction using
the GDB/MI interface.  In these examples, `->' means that the following
line is passed to GDB/MI as input, while `<-' means the output received
from GDB/MI.

Target Stop
...........

   Here's an example of stopping the inferior process:

     -> -stop
     <- (gdb)

and later:

     <- *stop,reason="stop",address="0x123",source="a.c:123"
     <- (gdb)

Simple CLI Command
..................

   Here's an example of a simple CLI command being passed through
GDB/MI and on to the CLI.

     -> print 1+2
     <- ~3\n
     <- (gdb)

Command With Side Effects
.........................

     -> -symbol-file xyz.exe
     <- *breakpoint,nr="3",address="0x123",source="a.c:123"
     <- (gdb)

A Bad Command
.............

   Here's what happens if you pass a non-existent command:

     -> -rubbish
     <- error,"Rubbish not found"
     <- (gdb)


File: gdb.info,  Node: GDB/MI Compatibility with CLI,  Next: GDB/MI Output Records,  Prev: GDB/MI Command Syntax,  Up: GDB/MI

GDB/MI Compatibility with CLI
=============================

   To help users familiar with GDB's existing CLI interface, GDB/MI
accepts existing CLI commands.  As specified by the syntax, such
commands can be directly entered into the GDB/MI interface and GDB will
respond.

   This mechanism is provided as an aid to developers of GDB/MI clients
and not as a reliable interface into the CLI.  Since the command is
being interpreteted in an environment that assumes GDB/MI behaviour,
the exact output of such commands is likely to end up being an
un-supported hybrid of GDB/MI and CLI output.


File: gdb.info,  Node: GDB/MI Output Records,  Next: GDB/MI Command Description Format,  Prev: GDB/MI Compatibility with CLI,  Up: GDB/MI

GDB/MI Output Records
=====================

* Menu:

* GDB/MI Result Records::
* GDB/MI Stream Records::
* GDB/MI Out-of-band Records::


File: gdb.info,  Node: GDB/MI Result Records,  Next: GDB/MI Stream Records,  Up: GDB/MI Output Records

GDB/MI Result Records
---------------------

   In addition to a number of out-of-band notifications, the response
to a GDB/MI command includes one of the following result indications:

`"^done" [ "," RESULTS ]'
     The synchronous operation was successful, `RESULTS' are the return
     values.

`"^running"'
     The asynchronous operation was successfully started.  The target is
     running.

`"^error" "," C-STRING'
     The operation failed.  The `C-STRING' contains the corresponding
     error message.


File: gdb.info,  Node: GDB/MI Stream Records,  Next: GDB/MI Out-of-band Records,  Prev: GDB/MI Result Records,  Up: GDB/MI Output Records

GDB/MI Stream Records
---------------------

   GDB internally maintains a number of output streams: the console, the
target, and the log.  The output intended for each of these streams is
funneled through the GDB/MI interface using "stream records".

   Each stream record begins with a unique "prefix character" which
identifies its stream (*note GDB/MI Output Syntax: GDB/MI Output
Syntax.).  In addition to the prefix, each stream record contains a
`STRING-OUTPUT'.  This is either raw text (with an implicit new line)
or a quoted C string (which does not contain an implicit newline).

`"~" STRING-OUTPUT'
     The console output stream contains text that should be displayed
     in the CLI console window.  It contains the textual responses to
     CLI commands.

`"@" STRING-OUTPUT'
     The target output stream contains any textual output from the
     running target.

`"&" STRING-OUTPUT'
     The log stream contains debugging messages being produced by GDB's
     internals.


File: gdb.info,  Node: GDB/MI Out-of-band Records,  Prev: GDB/MI Stream Records,  Up: GDB/MI Output Records

GDB/MI Out-of-band Records
--------------------------

   "Out-of-band" records are used to notify the GDB/MI client of
additional changes that have occurred.  Those changes can either be a
consequence of GDB/MI (e.g., a breakpoint modified) or a result of
target activity (e.g., target stopped).

   The following is a preliminary list of possible out-of-band records.

`"*" "stop"'

File: gdb.info,  Node: GDB/MI Command Description Format,  Next: GDB/MI Breakpoint Table Commands,  Prev: GDB/MI Output Records,  Up: GDB/MI

GDB/MI Command Description Format
=================================

   The remaining sections describe blocks of commands.  Each block of
commands is laid out in a fashion similar to this section.

   Note the the line breaks shown in the examples are here only for
readability.  They don't appear in the real output.  Also note that the
commands with a non-available example (N.A.) are not yet implemented.

Motivation
----------

   The motivation for this collection of commands.

Introduction
------------

   A brief introduction to this collection of commands as a whole.

Commands
--------

   For each command in the block, the following is described:

Synopsis
........

      -command ARGS...

GDB Command
...........

   The corresponding GDB CLI command.

Result
......

Out-of-band
...........

Notes
.....

Example
.......