Subversion Repositories openrisc_2011-10-31

INFO-DIR-SECTION Software development

INFO-DIR-SECTION Software development

START-INFO-DIR-ENTRY

START-INFO-DIR-ENTRY

* Gdb: (gdb).                     The GNU debugger.

* Gdb: (gdb).                     The GNU debugger.

END-INFO-DIR-ENTRY

END-INFO-DIR-ENTRY

developing GNU and promoting software freedom."

developing GNU and promoting software freedom."

   This file documents the GNU debugger GDB.

   This file documents the GNU debugger GDB.

   This is the Ninth Edition, of `Debugging with GDB: the GNU

   This is the Ninth Edition, of `Debugging with GDB: the GNU

   Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,

   Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,

1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,

1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,

2010 Free Software Foundation, Inc.

2010 Free Software Foundation, Inc.

Debugging with GDB

Debugging with GDB

******************

******************

This file describes GDB, the GNU symbolic debugger.

This file describes GDB, the GNU symbolic debugger.

   Copyright (C) 1988-2010 Free Software Foundation, Inc.

   Copyright (C) 1988-2010 Free Software Foundation, Inc.

   This edition of the GDB manual is dedicated to the memory of Fred

   This edition of the GDB manual is dedicated to the memory of Fred

Fish.  Fred was a long-standing contributor to GDB and to Free software

Fish.  Fred was a long-standing contributor to GDB and to Free software

   * Change things in your program, so you can experiment with

   * Change things in your program, so you can experiment with

     correcting the effects of one bug and go on to learn about another.

     correcting the effects of one bug and go on to learn about another.

   You can use GDB to debug programs written in C and C++.  For more

   You can use GDB to debug programs written in C and C++.  For more

   Support for Modula-2 is partial.  For information on Modula-2, see

   Support for Modula-2 is partial.  For information on Modula-2, see

   Debugging Pascal programs which use sets, subranges, file variables,

   Debugging Pascal programs which use sets, subranges, file variables,

or nested functions does not currently work.  GDB does not support

or nested functions does not currently work.  GDB does not support

entering expressions, printing values, or similar features using Pascal

entering expressions, printing values, or similar features using Pascal

syntax.

syntax.

John Newlin, and Scott Foehner.

John Newlin, and Scott Foehner.

   Michael Eager and staff of Xilinx, Inc., contributed support for the

   Michael Eager and staff of Xilinx, Inc., contributed support for the

Xilinx MicroBlaze architecture.

Xilinx MicroBlaze architecture.

File: gdb.info,  Node: Sample Session,  Next: Invocation,  Prev: Summary,  Up: Top

File: gdb.info,  Node: Sample Session,  Next: Invocation,  Prev: Summary,  Up: Top

1 A Sample GDB Session

1 A Sample GDB Session

**********************

**********************

      of it under certain conditions; type "show copying" to see

      of it under certain conditions; type "show copying" to see

      the conditions.

      the conditions.

     There is absolutely no warranty for GDB; type "show warranty"

     There is absolutely no warranty for GDB; type "show warranty"

      for details.

      for details.

     (gdb)

     (gdb)

GDB reads only enough symbol data to know where to find the rest when

GDB reads only enough symbol data to know where to find the rest when

needed; as a result, the first prompt comes up very quickly.  We now

needed; as a result, the first prompt comes up very quickly.  We now

tell GDB to use a narrower display width than usual, so that examples

tell GDB to use a narrower display width than usual, so that examples

   A blank line as input to GDB (typing just ) means to repeat the

   A blank line as input to GDB (typing just ) means to repeat the

previous command.  Certain commands (for example, `run') will not

previous command.  Certain commands (for example, `run') will not

repeat this way; these are commands whose unintentional repetition

repeat this way; these are commands whose unintentional repetition

might cause trouble and which you are unlikely to want to repeat.

might cause trouble and which you are unlikely to want to repeat.

Define.

Define.

   The `list' and `x' commands, when you repeat them with ,

   The `list' and `x' commands, when you repeat them with ,

construct new arguments rather than repeating exactly as typed.  This

construct new arguments rather than repeating exactly as typed.  This

permits easy scanning of source or memory.

permits easy scanning of source or memory.

In general, GDB can tell that a quote is needed (and inserts it) if you

In general, GDB can tell that a quote is needed (and inserts it) if you

have not yet started typing the argument list when you ask for

have not yet started typing the argument list when you ask for

completion on an overloaded symbol.

completion on an overloaded symbol.

Expressions: C Plus Plus Expressions.  You can use the command `set

Expressions: C Plus Plus Expressions.  You can use the command `set

Features for C++: Debugging C Plus Plus.

Features for C++: Debugging C Plus Plus.

   When completing in an expression which looks up a field in a

   When completing in an expression which looks up a field in a

structure, GDB also tries(1) to limit completions to the field names

structure, GDB also tries(1) to limit completions to the field names

available in the type of the left-hand-side:

available in the type of the left-hand-side:

   GCC, the GNU C/C++ compiler, supports `-g' with or without `-O',

   GCC, the GNU C/C++ compiler, supports `-g' with or without `-O',

making it possible to debug optimized code.  We recommend that you

making it possible to debug optimized code.  We recommend that you

_always_ use `-g' whenever you compile a program.  You may think your

_always_ use `-g' whenever you compile a program.  You may think your

program is correct, but there is no sense in pushing your luck.  For

program is correct, but there is no sense in pushing your luck.  For

   Older versions of the GNU C compiler permitted a variant option

   Older versions of the GNU C compiler permitted a variant option

`-gg' for debugging information.  GDB no longer supports this format;

`-gg' for debugging information.  GDB no longer supports this format;

if your GNU C compiler has this option, do not use it.

if your GNU C compiler has this option, do not use it.

     underlying `run' command.  Note that the same arguments will be

     underlying `run' command.  Note that the same arguments will be

     reused if no argument is provided during subsequent calls to

     reused if no argument is provided during subsequent calls to

     `start' or `run'.

     `start' or `run'.

     It is sometimes necessary to debug the program during elaboration.

     It is sometimes necessary to debug the program during elaboration.

`set exec-wrapper WRAPPER'

`set exec-wrapper WRAPPER'

`show exec-wrapper'

`show exec-wrapper'

`unset exec-wrapper'

`unset exec-wrapper'

     When `exec-wrapper' is set, the specified wrapper is used to

     When `exec-wrapper' is set, the specified wrapper is used to

when a certain kind of event occurs, such as the throwing of a C++

when a certain kind of event occurs, such as the throwing of a C++

exception or the loading of a library.  As with watchpoints, you use a

exception or the loading of a library.  As with watchpoints, you use a

different command to set a catchpoint (*note Setting Catchpoints: Set

different command to set a catchpoint (*note Setting Catchpoints: Set

Catchpoints.), but aside from that, you can manage a catchpoint like any

Catchpoints.), but aside from that, you can manage a catchpoint like any

other breakpoint.  (To stop when your program receives a signal, use the

other breakpoint.  (To stop when your program receives a signal, use the

   GDB assigns a number to each breakpoint, watchpoint, or catchpoint

   GDB assigns a number to each breakpoint, watchpoint, or catchpoint

when you create it; these numbers are successive integers starting with

when you create it; these numbers are successive integers starting with

one.  In many of the commands for controlling various features of

one.  In many of the commands for controlling various features of

breakpoints you use the breakpoint number to say which breakpoint you

breakpoints you use the breakpoint number to say which breakpoint you

5.1.1 Setting Breakpoints

5.1.1 Setting Breakpoints

-------------------------

-------------------------

Breakpoints are set with the `break' command (abbreviated `b').  The

Breakpoints are set with the `break' command (abbreviated `b').  The

debugger convenience variable `$bpnum' records the number of the

debugger convenience variable `$bpnum' records the number of the

Convenience Vars, for a discussion of what you can do with convenience

Convenience Vars, for a discussion of what you can do with convenience

variables.

variables.

`break LOCATION'

`break LOCATION'

     Set a breakpoint at the given LOCATION, which can specify a

     Set a breakpoint at the given LOCATION, which can specify a

     only two data breakpoints can be set at a time, and GDB will

     only two data breakpoints can be set at a time, and GDB will

     reject this command if more than two are used.  Delete or disable

     reject this command if more than two are used.  Delete or disable

     unused hardware breakpoints before setting new ones (*note

     unused hardware breakpoints before setting new ones (*note

     Disabling Breakpoints: Disabling.).  *Note Break Conditions:

     Disabling Breakpoints: Disabling.).  *Note Break Conditions:

     Conditions.  For remote targets, you can restrict the number of

     Conditions.  For remote targets, you can restrict the number of

     hardware-breakpoint-limit::.

     hardware-breakpoint-limit::.

`thbreak ARGS'

`thbreak ARGS'

     Set a hardware-assisted breakpoint enabled only for one stop.  ARGS

     Set a hardware-assisted breakpoint enabled only for one stop.  ARGS

     are the same as for the `hbreak' command and the breakpoint is set

     are the same as for the `hbreak' command and the breakpoint is set

     in the same way.  However, like the `tbreak' command, the

     in the same way.  However, like the `tbreak' command, the

     breakpoint is automatically deleted after the first time your

     breakpoint is automatically deleted after the first time your

     program stops there.  Also, like the `hbreak' command, the

     program stops there.  Also, like the `hbreak' command, the

     breakpoint requires hardware support and some target hardware may

     breakpoint requires hardware support and some target hardware may

     not have this support.  *Note Disabling Breakpoints: Disabling.

     not have this support.  *Note Disabling Breakpoints: Disabling.

`rbreak REGEX'

`rbreak REGEX'

     Set breakpoints on all functions matching the regular expression

     Set breakpoints on all functions matching the regular expression

     REGEX.  This command sets an unconditional breakpoint on all

     REGEX.  This command sets an unconditional breakpoint on all

     matches, printing a list of all breakpoints it set.  Once these

     matches, printing a list of all breakpoints it set.  Once these

          Enabled breakpoints are marked with `y'.  `n' marks

          Enabled breakpoints are marked with `y'.  `n' marks

          breakpoints that are not enabled.

          breakpoints that are not enabled.

    _Address_

    _Address_

          Where the breakpoint is in your program, as a memory address.

          Where the breakpoint is in your program, as a memory address.

          breakpoint with several locations will have `' in

          breakpoint with several locations will have `' in

          this field--see below for details.

          this field--see below for details.

    _What_

    _What_

          Where the breakpoint is in the source for your program, as a

          Where the breakpoint is in the source for your program, as a

`show can-use-hw-watchpoints'

`show can-use-hw-watchpoints'

     Show the current mode of using hardware watchpoints.

     Show the current mode of using hardware watchpoints.

   For remote targets, you can restrict the number of hardware

   For remote targets, you can restrict the number of hardware

hardware-breakpoint-limit::.

hardware-breakpoint-limit::.

   When you issue the `watch' command, GDB reports

   When you issue the `watch' command, GDB reports

     Hardware watchpoint NUM: EXPR

     Hardware watchpoint NUM: EXPR

   Except for a breakpoint set with `tbreak' (*note Setting

   Except for a breakpoint set with `tbreak' (*note Setting

Breakpoints: Set Breaks.), breakpoints that you set are initially

Breakpoints: Set Breaks.), breakpoints that you set are initially

enabled; subsequently, they become disabled or enabled only when you

enabled; subsequently, they become disabled or enabled only when you

use one of the commands above.  (The command `until' can set and delete

use one of the commands above.  (The command `until' can set and delete

a breakpoint of its own, but it does not change the state of your other

a breakpoint of its own, but it does not change the state of your other

Stepping.)

Stepping.)

File: gdb.info,  Node: Conditions,  Next: Break Commands,  Prev: Disabling,  Up: Breakpoints

File: gdb.info,  Node: Conditions,  Next: Break Commands,  Prev: Disabling,  Up: Breakpoints

`until LOCATION'

`until LOCATION'

`u LOCATION'

`u LOCATION'

     Continue running your program until either the specified location

     Continue running your program until either the specified location

     is reached, or the current stack frame returns.  LOCATION is any of

     is reached, or the current stack frame returns.  LOCATION is any of

     command uses temporary breakpoints, and hence is quicker than

     command uses temporary breakpoints, and hence is quicker than

     `until' without an argument.  The specified location is actually

     `until' without an argument.  The specified location is actually

     reached only if it is in the current frame.  This implies that

     reached only if it is in the current frame.  This implies that

     `until' can be used to skip over recursive function invocations.

     `until' can be used to skip over recursive function invocations.

     For instance in the code below, if the current location is line

     For instance in the code below, if the current location is line

          100     }

          100     }

`advance LOCATION'

`advance LOCATION'

     Continue running the program up to the given LOCATION.  An

     Continue running the program up to the given LOCATION.  An

     argument is required, which should be of one of the forms

     argument is required, which should be of one of the forms

     upon exit from the current stack frame.  This command is similar

     upon exit from the current stack frame.  This command is similar

     to `until', but `advance' will not skip over recursive function

     to `until', but `advance' will not skip over recursive function

     calls, and the target location doesn't have to be in the same

     calls, and the target location doesn't have to be in the same

     frame as the current one.

     frame as the current one.

`set schedule-multiple'

`set schedule-multiple'

     Set the mode for allowing threads of multiple processes to be

     Set the mode for allowing threads of multiple processes to be

     resumed when an execution command is issued.  When `on', all

     resumed when an execution command is issued.  When `on', all

     threads of all processes are allowed to run.  When `off', only the

     threads of all processes are allowed to run.  When `off', only the

     threads of the current process are resumed.  The default is `off'.

     threads of the current process are resumed.  The default is `off'.

`show schedule-multiple'

`show schedule-multiple'

     Display the current mode for resuming the execution of threads of

     Display the current mode for resuming the execution of threads of

     multiple processes.

     multiple processes.

`until'

`until'

     *Note until: Continuing and Stepping.

     *Note until: Continuing and Stepping.

   Background execution is especially useful in conjunction with

   Background execution is especially useful in conjunction with

Non-Stop Mode::.  However, you can also use these commands in the

Non-Stop Mode::.  However, you can also use these commands in the

normal all-stop mode with the restriction that you cannot issue another

normal all-stop mode with the restriction that you cannot issue another

execution command until the previous one finishes.  Examples of

execution command until the previous one finishes.  Examples of

commands that are valid in all-stop mode while the program is running

commands that are valid in all-stop mode while the program is running

include `help' and `info break'.

include `help' and `info break'.

for line `993' of `builtin.c'.

for line `993' of `builtin.c'.

The value of parameter `data' in frame 1 has been replaced by `...'.

The value of parameter `data' in frame 1 has been replaced by `...'.

By default, GDB prints the value of a parameter only if it is a scalar

By default, GDB prints the value of a parameter only if it is a scalar

(integer, pointer, enumeration, etc).  See command `set print

(integer, pointer, enumeration, etc).  See command `set print

configure the way function parameter values are printed.

configure the way function parameter values are printed.

   If your program was compiled with optimizations, some compilers will

   If your program was compiled with optimizations, some compilers will

optimize away arguments passed to functions if those arguments are

optimize away arguments passed to functions if those arguments are

never used after the call.  Such optimizations generate code that

never used after the call.  Such optimizations generate code that

(*note Selecting a Frame: Selection.), GDB prints the line where

(*note Selecting a Frame: Selection.), GDB prints the line where

execution in that frame has stopped.  You can print other portions of

execution in that frame has stopped.  You can print other portions of

source files by explicit command.

source files by explicit command.

   If you use GDB through its GNU Emacs interface, you may prefer to

   If you use GDB through its GNU Emacs interface, you may prefer to

Emacs: Emacs.

Emacs: Emacs.

* Menu:

* Menu:

* List::                        Printing source lines

* List::                        Printing source lines

9.1 Printing Source Lines

9.1 Printing Source Lines

=========================

=========================

To print lines from a source file, use the `list' command (abbreviated

To print lines from a source file, use the `list' command (abbreviated

`l').  By default, ten lines are printed.  There are several ways to

`l').  By default, ten lines are printed.  There are several ways to

Location::, for the full list.

Location::, for the full list.

   Here are the forms of the `list' command most commonly used:

   Here are the forms of the `list' command most commonly used:

`list LINENUM'

`list LINENUM'

manage a list of source path substitution rules.  A "substitution rule"

manage a list of source path substitution rules.  A "substitution rule"

specifies how to rewrite source directories stored in the program's

specifies how to rewrite source directories stored in the program's

debug information in case the sources were moved to a different

debug information in case the sources were moved to a different

directory between compilation and debugging.  A rule is made of two

directory between compilation and debugging.  A rule is made of two

strings, the first specifying what needs to be rewritten in the path,

strings, the first specifying what needs to be rewritten in the path,

substitute-path::, we name these two parts FROM and TO respectively.

substitute-path::, we name these two parts FROM and TO respectively.

GDB does a simple string replacement of FROM with TO at the start of

GDB does a simple string replacement of FROM with TO at the start of

the directory part of the source file name, and uses that result

the directory part of the source file name, and uses that result

instead of the original file name to look up the sources.

instead of the original file name to look up the sources.

`info line' prints addresses in symbolic form as well as hex.

`info line' prints addresses in symbolic form as well as hex.

`info line LINESPEC'

`info line LINESPEC'

     Print the starting and ending addresses of the compiled code for

     Print the starting and ending addresses of the compiled code for

     source line LINESPEC.  You can specify source lines in any of the

     source line LINESPEC.  You can specify source lines in any of the

   For example, we can use `info line' to discover the location of the

   For example, we can use `info line' to discover the location of the

object code for the first line of function `m4_changequote':

object code for the first line of function `m4_changequote':

     (gdb) info line m4_changequote

     (gdb) info line m4_changequote

`print EXPR'

`print EXPR'

`print /F EXPR'

`print /F EXPR'

     EXPR is an expression (in the source language).  By default the

     EXPR is an expression (in the source language).  By default the

     value of EXPR is printed in a format appropriate to its data type;

     value of EXPR is printed in a format appropriate to its data type;

     you can choose a different format by specifying `/F', where F is a

     you can choose a different format by specifying `/F', where F is a

     Formats.

     Formats.

`print'

`print'

`print /F'

`print /F'

     If you omit EXPR, GDB displays the last value again (from the

     If you omit EXPR, GDB displays the last value again (from the

`print' and many other GDB commands accept an expression and compute

`print' and many other GDB commands accept an expression and compute

its value.  Any kind of constant, variable or operator defined by the

its value.  Any kind of constant, variable or operator defined by the

programming language you are using is valid in an expression in GDB.

programming language you are using is valid in an expression in GDB.

This includes conditional expressions, function calls, casts, and

This includes conditional expressions, function calls, casts, and

string constants.  It also includes preprocessor macros, if you

string constants.  It also includes preprocessor macros, if you

Compilation::.

Compilation::.

   GDB supports array constants in expressions input by the user.  The

   GDB supports array constants in expressions input by the user.  The

syntax is {ELEMENT, ELEMENT...}.  For example, you can use the command

syntax is {ELEMENT, ELEMENT...}.  For example, you can use the command

`print {1, 2, 3}' to create an array of three integers.  If you pass an

`print {1, 2, 3}' to create an array of three integers.  If you pass an

expression.  For example, `p/x' reprints the last value in hex.

expression.  For example, `p/x' reprints the last value in hex.

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

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

   (1) `b' cannot be used because these format letters are also used

   (1) `b' cannot be used because these format letters are also used

Memory: Memory.

Memory: Memory.

File: gdb.info,  Node: Memory,  Next: Auto Display,  Prev: Output Formats,  Up: Data

File: gdb.info,  Node: Memory,  Next: Auto Display,  Prev: Output Formats,  Up: Data

you want to see three machine instructions, including any operands.

you want to see three machine instructions, including any operands.

For convenience, especially when used with the `display' command, the

For convenience, especially when used with the `display' command, the

`i' format also prints branch delay slot instructions, if any, beyond

`i' format also prints branch delay slot instructions, if any, beyond

the count specified, which immediately follow the last instruction that

the count specified, which immediately follow the last instruction that

is within the count.  The command `disassemble' gives an alternative

is within the count.  The command `disassemble' gives an alternative

Code: Machine Code.

Code: Machine Code.

   All the defaults for the arguments to `x' are designed to make it

   All the defaults for the arguments to `x' are designed to make it

easy to continue scanning memory with minimal specifications each time

easy to continue scanning memory with minimal specifications each time

you use `x'.  For example, after you have inspected three machine

you use `x'.  For example, after you have inspected three machine