NetBSD/gnu/dist/gdb/doc/annotate.texi

\input texinfo   @c -*-texinfo-*-
@c %**start of header
@setfilename annotate.info
@settitle GDB Annotations
@setchapternewpage off
@c %**end of header

@set EDITION 0.5
@set DATE May 1994

@ifinfo
This file documents GDB annotations.

This is Edition @value{EDITION}, @value{DATE}, of @cite{GDB
Annotations}.  Copyright 1994 Free Software Foundation

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through TeX and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided also that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions.
@end ifinfo

@titlepage
@title GDB Annotations
@subtitle Edition @value{EDITION}
@subtitle @value{DATE}
@author Cygnus Support
@page
@vskip 0pt plus 1filll
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

Copyright @copyright{} 1994 Free Software Foundation
@end titlepage

@ifinfo
@node Top
@top GDB Annotations

This file describes annotations in GDB, the GNU symbolic debugger.
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.

This is Edition @value{EDITION}, @value{DATE}.

@menu
* General::             What annotations are; the general syntax.
* Server::              Issuing a command without affecting user state.
* Values::              Values are marked as such.
* Frames::              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.
* Running::             Whether the program is running, how it stopped, etc.
* Source::              Annotations describing source code.
* TODO::                Annotations which might be added in the future.
* Index::               Index
@end menu
@end ifinfo

@node General
@chapter What is an Annotation?

To produce annotations, start GDB with the @code{--annotate=2} option.

Annotations start with a newline character, two @samp{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 @samp{control-z}
characters denotes literal output from GDB.  Currently there is no need
for GDB to output a newline followed by two @samp{control-z} characters,
but if there was such a need, the annotations could be extended with an
@samp{escape} annotation which means those three characters as output.

A simple example of starting up GDB with annotations is:

@example
$ gdb --annotate=2
GDB is free software and you are welcome to 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.
GDB 4.12.3 (sparc-sun-sunos4.1.3), 
Copyright 1994 Free Software Foundation, Inc.

^Z^Zpre-prompt
(gdb) 
^Z^Zprompt
quit

^Z^Zpost-prompt
$ 
@end example

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

@node Server
@chapter The Server Prefix

To issue a command to GDB without affecting certain aspects of the state
which is seen by users, prefix it with @samp{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 @key{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 @code{output} command instead of the @code{print} command.

@node Values
@chapter Values

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

@findex value-history-begin
@findex value-history-value
@findex value-history-end
If a value is printed using @code{print} and added to the value history,
the annotation looks like

@example
^Z^Zvalue-history-begin @var{history-number} @var{value-flags}
@var{history-string}
^Z^Zvalue-history-value
@var{the-value}
^Z^Zvalue-history-end
@end example

where @var{history-number} is the number it is getting in the value
history, @var{history-string} is a string, such as @samp{$5 = }, which
introduces the value to the user, @var{the-value} is the output
corresponding to the value itself, and @var{value-flags} is @samp{*} for
a value which can be dereferenced and @samp{-} for a value which cannot.

@findex value-begin
@findex value-end
If the value is not added to the value history (it is an invalid float
or it is printed with the @code{output} command), the annotation is similar:

@example
^Z^Zvalue-begin @var{value-flags}
@var{the-value}
^Z^Zvalue-end
@end example

@findex arg-begin
@findex arg-name-end
@findex arg-value
@findex arg-end
When GDB prints an argument to a function (for example, in the output
from the @code{backtrace} command), it annotates it as follows:

@example
^Z^Zarg-begin
@var{argument-name}
^Z^Zarg-name-end
@var{separator-string}
^Z^Zarg-value @var{value-flags}
@var{the-value}
^Z^Zarg-end
@end example

where @var{argument-name} is the name of the argument,
@var{separator-string} is text which separates the name from the value
for the user's benefit (such as @samp{=}), and @var{value-flags} and
@var{the-value} have the same meanings as in a
@code{value-history-begin} annotation.

@findex field-begin
@findex field-name-end
@findex field-value
@findex field-end
When printing a structure, GDB annotates it as follows:

@example
^Z^Zfield-begin @var{value-flags}
@var{field-name}
^Z^Zfield-name-end
@var{separator-string}
^Z^Zfield-value
@var{the-value}
^Z^Zfield-end
@end example

where @var{field-name} is the name of the field, @var{separator-string}
is text which separates the name from the value for the user's benefit
(such as @samp{=}), and @var{value-flags} and @var{the-value} have the
same meanings as in a @code{value-history-begin} annotation.

When printing an array, GDB annotates it as follows:

@example
^Z^Zarray-section-begin @var{array-index} @var{value-flags}
@end example

where @var{array-index} is the index of the first element being
annotated and @var{value-flags} has the same meaning as in a
@code{value-history-begin} annotation.  This is followed by any number
of elements, where is element can be either a single element:

@findex elt
@example
@samp{,} @var{whitespace}         ; @r{omitted for the first element}
@var{the-value}
^Z^Zelt
@end example

or a repeated element

@findex elt-rep
@findex elt-rep-end
@example
@samp{,} @var{whitespace}         ; @r{omitted for the first element}
@var{the-value}
^Z^Zelt-rep @var{number-of-repititions}
@var{repetition-string}
^Z^Zelt-rep-end
@end example

In both cases, @var{the-value} is the output for the value of the
element and @var{whitespace} can contain spaces, tabs, and newlines.  In
the repeated case, @var{number-of-repititons} is the number of
consecutive array elements which contain that value, and
@var{repetition-string} is a string which is designed to convey to the
user that repitition is being depicted.

@findex array-section-end
Once all the array elements have been output, the array annotation is
ended with

@example
^Z^Zarray-section-end
@end example

@node Frames
@chapter Frames

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

@findex frame-begin
The frame annotation begins with

@example
^Z^Zframe-begin @var{level} @var{address}
@var{level-string}
@end example

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

@findex frame-end
@example
^Z^Zframe-end
@end example

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

@itemize @bullet
@item
@findex function-call
@example
^Z^Zfunction-call
@var{function-call-string}
@end example

where @var{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.

@item
@findex signal-handler-caller
@example
^Z^Zsignal-handler-caller
@var{signal-handler-caller-string}
@end example

where @var{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).

@item
A normal frame.

@findex frame-address
@findex frame-address-end
This can optionally (depending on whether this is thought of as
interesting information for the user to see) begin with

@example
^Z^Zframe-address
@var{address}
^Z^Zframe-address-end
@var{separator-string}
@end example

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

@findex frame-function-name
@findex frame-args
Then comes

@example
^Z^Zframe-function-name
@var{function-name}
^Z^Zframe-args
@var{arguments}
@end example

where @var{function-name} is the name of the function executing in the
frame, or @samp{??} if not known, and @var{arguments} are the arguments
to the frame, with parentheses around them (each argument is annotated
individually as well @pxref{Values}).

@findex frame-source-begin
@findex frame-source-file
@findex frame-source-file-end
@findex frame-source-line
@findex frame-source-end
If source information is available, a reference to it is then printed:

@example
^Z^Zframe-source-begin
@var{source-intro-string}
^Z^Zframe-source-file
@var{filename}
^Z^Zframe-source-file-end
:
^Z^Zframe-source-line
@var{line-number}
^Z^Zframe-source-end
@end example

where @var{source-intro-string} separates for the user's benefit the
reference from the text which precedes it, @var{filename} is the name of
the source file, and @var{line-number} is the line number within that
file (the first line is line 1).

@findex frame-where
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

@example
^Z^Zframe-where
@var{information}
@end example

Then, if source is to actually be displayed for this frame (for example,
this is not true for output from the @code{backtrace} command), then a
@code{source} annotation (@pxref{Source}) is displayed.  Unlike most
annotations, this is output instead of the normal text which would be
output, not in addition.
@end itemize

@node Displays
@chapter Displays

@findex display-begin
@findex display-number-end
@findex display-format
@findex display-expression
@findex display-expression-end
@findex display-value
@findex display-end
When GDB is told to display something using the @code{display} command,
the results of the display are annotated:

@example
^Z^Zdisplay-begin
@var{number}
^Z^Zdisplay-number-end
@var{number-separator}
^Z^Zdisplay-format
@var{format}
^Z^Zdisplay-expression
@var{expression}
^Z^Zdisplay-expression-end
@var{expression-separator}
^Z^Zdisplay-value
@var{value}
^Z^Zdisplay-end
@end example

where @var{number} is the number of the display, @var{number-separator}
is intended to separate the number from what follows for the user,
@var{format} includes information such as the size, format, or other
information about how the value is being displayed, @var{expression} is
the expression being displayed, @var{expression-separator} is intended
to separate the expression from the text that follows for the user,
and @var{value} is the actual value being displayed.

@node Prompting
@chapter 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 @dfn{input type}.  Each
input type has three annotations: a @code{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 @code{post-}
annotation which denotes the end of any echo which may (or may not) be
associated with the input.  For example, the @code{prompt} input type
features the following annotations:

@example
^Z^Zpre-prompt
^Z^Zprompt
^Z^Zpost-prompt
@end example

The input types are

@table @code
@findex pre-prompt
@findex prompt
@findex post-prompt
@item prompt
When GDB is prompting for a command (the main GDB prompt).

@findex pre-commands
@findex commands
@findex post-commands
@item commands
When GDB prompts for a set of commands, like in the @code{commands}
command.  The annotations are repeated for each command which is input.

@findex pre-overload-choice
@findex overload-choice
@findex post-overload-choice
@item overload-choice
When GDB wants the user to select between various overloaded functions.

@findex pre-query
@findex query
@findex post-query
@item query
When GDB wants the user to confirm a potentially dangerous operation.

@findex pre-prompt-for-continue
@findex prompt-for-continue
@findex post-prompt-for-continue
@item prompt-for-continue
When GDB is asking the user to press return to continue.  Note: Don't
expect this to work well; instead use @code{set height 0} to disable
prompting.  This is because the counting of lines is buggy in the
presence of annotations.
@end table

@node Errors
@chapter Errors

@findex quit
@example
^Z^Zquit
@end example

This annotation occurs right before GDB responds to an interrupt.

@findex error
@example
^Z^Zerror
@end example

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
@code{value-history-begin} annotation is followed by a @code{error}, one
cannot expect to receive the matching @code{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.

@findex error-begin
A quit or error annotation may be preceded by

@example
^Z^Zerror-begin
@end example

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

Warning messages are not yet annotated.
@c If we want to change that, need to fix warning(), type_error(),
@c range_error(), and possibly other places.

@node Breakpoint Info
@chapter Information on Breakpoints

The output from the @code{info breakpoints} command is annotated as follows:

@findex breakpoints-headers
@findex breakpoints-table
@example
^Z^Zbreakpoints-headers
@var{header-entry}
^Z^Zbreakpoints-table
@end example

where @var{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:

@findex record
@findex field
@example
^Z^Zrecord
^Z^Zfield 0
@var{number}
^Z^Zfield 1
@var{type}
^Z^Zfield 2
@var{disposition}
^Z^Zfield 3
@var{enable}
^Z^Zfield 4
@var{address}
^Z^Zfield 5
@var{what}
^Z^Zfield 6
@var{frame}
^Z^Zfield 7
@var{condition}
^Z^Zfield 8
@var{ignore-count}
^Z^Zfield 9
@var{commands}
@end example

Note that @var{address} is intended for user consumption---the syntax
varies depending on the language.

The output ends with

@findex breakpoints-table-end
@example
^Z^Zbreakpoints-table-end
@end example

@node Invalidation
@chapter Invalidation Notices

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

@table @code
@findex frames-invalid
@item ^Z^Zframes-invalid

The frames (for example, output from the @code{backtrace} command) may
have changed.

@findex breakpoints-invalid
@item ^Z^Zbreakpoints-invalid

The breakpoints may have changed.  For example, the user just added or
deleted a breakpoint.
@end table

@node Running
@chapter Running the Program

@findex starting
@findex stopping
When the program starts executing due to a GDB command such as
@code{step} or @code{continue}, 

@example
^Z^Zstarting
@end example

is output.  When the program stops, 

@example
^Z^Zstopped
@end example

is output.  Before the @code{stopped} annotation, a variety of
annotations describe how the program stopped.

@table @code
@findex exited
@item ^Z^Zexited @var{exit-status}
The program exited, and @var{exit-status} is the exit status (zero for
successful exit, otherwise nonzero).

@findex signalled
@findex signal-name
@findex signal-name-end
@findex signal-string
@findex signal-string-end
@item ^Z^Zsignalled
The program exited with a signal.  After the @code{^Z^Zsignalled}, the
annotation continues:

@example
@var{intro-text}
^Z^Zsignal-name
@var{name}
^Z^Zsignal-name-end
@var{middle-text}
^Z^Zsignal-string
@var{string}
^Z^Zsignal-string-end
@var{end-text}
@end example

where @var{name} is the name of the signal, such as @code{SIGILL} or
@code{SIGSEGV}, and @var{string} is the explanation of the signal, such
as @code{Illegal Instruction} or @code{Segmentation fault}.
@var{intro-text}, @var{middle-text}, and @var{end-text} are for the
user's benefit and have no particular format.

@findex signal
@item ^Z^Zsignal
The syntax of this annotation is just like @code{signalled}, but GDB is
just saying that the program received the signal, not that it was
terminated with it.

@findex breakpoint
@item ^Z^Zbreakpoint @var{number}
The program hit breakpoint number @var{number}.

@findex watchpoint
@item ^Z^Zwatchpoint @var{number}
The program hit watchpoint number @var{number}.
@end table

@node Source
@chapter Displaying Source

@findex source
The following annotation is used instead of displaying source code:

@example
^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
@end example

where @var{filename} is an absolute file name indicating which source
file, @var{line} is the line number within that file (where 1 is the
first line in the file), @var{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),
@var{middle} is @samp{middle} if @var{addr} is in the middle of the
line, or @samp{beg} if @var{addr} is at the beginning of the line, and
@var{addr} is the address in the target program associated with the
source which is being displayed.  @var{addr} is in the form @samp{0x}
followed by one or more lowercase hex digits (note that this does not
depend on the language).

@node TODO
@chapter Annotations We Might Want in the Future

@format
    - 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.
@end format

@node Index
@unnumbered Index

@printindex fn

@bye