Backtrace

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⇤ ← Revision 10 as of 2006-05-21 18:38:02 →
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Editor: dslb-084-058-169-229
Comment: how to attach to a running program
← Revision 16 as of 2007-01-20 02:13:51 → ⇥
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Editor: fw
Comment:
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apt-get install gdb sudo apt-get install gdb
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(gdb) info registers
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= backtrace of an already running program = = Already running programs =
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This applies to debugging i.e. panel applets. You can ask GDB to attach to a program that's already running. This is useful for debugging things that start up, but crash when you perform a particular task.
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 1. Find the PID (process ID) of <program>: {{{
ps ax | grep <program>		  1. Find the process ID of <program>: {{{
pidof <program>
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gdb | tee gdb-<program>.txt gdb 2>&1 | tee gdb-<program>.txt
(gdb) handle SIG33 pass nostop noprint
(gdb) set pagination 0
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 1. The program will continue running. Perform any actions necessary to reproduce the crash
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(gdb) info registers
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Note that you can also set logging to a file like this: {{{
(gdb) set logging file gdb-<program>.txt
(gdb) set logging on
}}}

= Other resources =
 * [http://live.gnome.org/GettingTraces Another useful how-to]

A backtrace shows a listing of which program functions are still active. Since functions are nested when they are called, the program must record where it left one function, to jump into an inner one. It does this on the stack, which we dump for the backtrace,

By getting a backtrace at the point of a bug, a developer may be able to isolate where that bug is, because it will narrow down to the function, or even the line, that caused the erroneous behaviour.

Generation

Please ensure you have packages with debug symbols installed. You can do this by following the instructions at DebuggingProgramCrash.

  1. Make sure the GNU Debugger is installed. 

    sudo apt-get install gdb

  2. Start the program under control of gdb: 

    gdb <program> 2>&1 | tee gdb-<program>.txt
(gdb) handle SIG33 pass nostop noprint
(gdb) set pagination 0
(gdb) run <arguments, if any>
  3. The program will start. Perform any actions necessary to reproduce the crash

  4. Retrieve a backtrace of the crash: 

    (gdb) backtrace
(gdb) info registers
(gdb) thread apply all backtrace

  5. Attach the complete output from GDB, contained in gdb-<program>.txt, in your bug report.

Already running programs

You can ask GDB to attach to a program that's already running. This is useful for debugging things that start up, but crash when you perform a particular task.

  1. Make sure the GNU Debugger is installed. 

    sudo apt-get install gdb

  2. Find the process ID of <program>: 

    pidof <program>

  3. Start gdb: 

    gdb 2>&1 | tee gdb-<program>.txt
(gdb) handle SIG33 pass nostop noprint
(gdb) set pagination 0
(gdb) attach <PID>

  4. Continue the <program>: 

    (gdb) continue
  5. The program will continue running. Perform any actions necessary to reproduce the crash

  6. Retrieve a backtrace of the crash: 

    (gdb) backtrace
(gdb) info registers
(gdb) thread apply all backtrace

  7. Attach the complete output from GDB, contained in gdb-<program>.txt, in your bug report.

Note that you can also set logging to a file like this: 

(gdb) set logging file gdb-<program>.txt
(gdb) set logging on

Other resources

Backtrace (last edited 2022-12-20 22:15:16 by sergiodj)