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Devel::bt(3pm) User Contributed Perl Documentation Devel::bt(3pm)


Devel::bt - Automatic gdb backtraces on errors


    $ perl -d:bt -MB -e'(bless \(my $o = 0), q{B::SV})->REFCNT'
    #0  0x00007f9c3215ab0e in __libc_waitpid (pid=<value optimized out>, stat_loc=0x7fff4c5ffbe8, options=<value optimized out>) at ../sysdeps/unix/sysv/linux/waitpid.c:32
    #1  0x00007f9c319168c1 in backtrace () at bt.xs:129
    #2  0x00007f9c319168ec in sighandler (sig=11) at bt.xs:135
    #3  <signal handler called>
    #4  0x00007f9c316c8ccf in XS_B__SV_REFCNT (my_perl=0x151c010, cv=0x177bfb8) at B.c:3360
    #5  0x000000000057d5a0 in Perl_pp_entersub (my_perl=0x151c010) at pp_hot.c:2882
    #6  0x000000000051a331 in Perl_runops_debug (my_perl=0x151c010) at dump.c:2049
    #7  0x0000000000454ab0 in S_run_body (my_perl=0x151c010, oldscope=1) at perl.c:2308
    #8  0x0000000000453d78 in perl_run (my_perl=0x151c010) at perl.c:2233
    #9  0x00000000004230fd in main (argc=6, argv=0x7fff4c600788, env=0x7fff4c6007c0) at perlmain.c:117


This module, when enabled, registers a handler for certain types of fatal errors, like segmentation faults, and, once such an error occurs, prints a debugger backtrace to standard output before exiting the program.

It is intended to be used to debug crashes in situations where running the failing program directly under a debugger is not possible, for example when trying to get more information from cpantesters or from users unfamiliar with gdb.


When being imported, a signal handler for the following signals is registered:
  • "SIGILL"
  • "SIGFPE"
  • "SIGBUS"

Once the program causes an error that results in one of the above signals being sent to it, the signal handler will be called, and fork off a process running "gdb" and generating a backtrace of the running program, which will then be printed to standard output.


This software is based on parts of "glib", which is written by:
  • Peter Mattis <>
  • Spencer Kimball <>
  • Josh MacDonald <>
  • Shawn T. Amundson <>
  • Jeff Garzik <>
  • Raja R Harinath <>
  • Tim Janik <>
  • Elliot Lee <>
  • Tor Lillqvist <>
  • Paolo Molaro <>
  • Havoc Pennington <>
  • Manish Singh <>
  • Owen Taylor <>
  • Sebastian Wilhelmi <>
  • and others

"glib" is licensed under The GNU Lesser General Public License, Version 2.


Florian Ragwitz <>


This software is Copyright (c) 2012 by Florian Ragwitz.

This is free software, licensed under:

  The GNU Lesser General Public License, Version 2.1, February 1999
2019-10-06 perl v5.30.0