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Accepted
Neil
Asked: 2009-09-03 11:09:00 +0800 CST

Can you get any program in Linux to print a stack trace if it segfaults?

  • 772

If I run a program from the shell, and it segfaults:

$ buggy_program
Segmentation fault

It will tell me, however, is there a way to get programs to print a backtrace, perhaps by running something like this:

$ print_backtrace_if_segfault buggy_program
Segfault in main.c:35
(rest of the backtrace)

I'd also rather not use strace or ltrace for that kind of information, as they'll print either way...

linux

6 Answers

  1. Best Answer

    There might be a better way, but this kind of automates it.

    Put the following in ~/backtrace:

    backtrace
quit

    Put this in a script called seg_wrapper.sh in a directory in your path:

    #!/bin/bash
ulimit -c unlimited
"$@"
if [[ $? -eq 139 ]]; then
    gdb -q $1 core -x ~/backtrace
fi

    The ulimit command makes it so the core is dumped. "$@" are the arguments given to the script, so it would be your program and its arguments. $? holds the exit status, 139 seems to be the default exit status for my machine for a segfault.

    For gdb, -q means quiet (no intro message), and -x tells gdb to execute commands in the file given to it.

    Usage

    So to use it you would just:

    seg_wrapper.sh ./mycommand and its arguments

    Update

    You could also write a signal handler that does this, see this link.

    • 31

  2. Sorry to come in here 2 years later ... stumbled upon while looking for something else. Adding this for completeness.

    1) While I think the accepted answer is great, it requires gdb. The method I am familiar with uses libSegFault.so.

    If you run your app with

    LD_PRELOAD=...path-to.../libSegFault.so myapp

    You would get a report with backtrace, loaded libs, etc

    2) A wrapper script catchsegv is also available that would attempt to use addr2line to translate addresses to filename + line number.

    These are much lighter solutions than core files or gdb (good for embedded systems for example)

    • 24

  3. catchsegv

    It was mentioned in another answer (but in no way focused on). It's a handy tool bundled with the glibc project. It will provide a backtrace (and other useful debug information) only if a program does indeed segfault.

    A good write up exists here.

    You can include it in your own scripts as you see fit.

    • 7

  4. You need everyone's friend GDB

    gdb <program> [core file]

    Once you've loaded your corefile, the command 'backtrace' (can be abbreviated to bt) will give you the current call stack. If you run your program from inside gdb, you can set arbitrary breakpoints and examine the memory contents, etc.

    • 6

  5. Ubuntu (as a project) uses Apport to do this. You can look how they did it.

    https://wiki.ubuntu.com/Apport

    • 4

  6. Here is a slightly modified variant of the script from Kyle Brandt. It is improved in the following ways:

    • do not require manual interaction if stack trace is long
    • some coredumps are saved with the name pattern core., respect this setting
    • do not require an explicit command file flying around for gdb (it will create a temporary one)
    • wait for background jobs

    Script:

    #!/bin/bash
gdbcommandfile=$(tempfile)
usepid=$(cat /proc/sys/kernel/core_uses_pid)
printf "set pagination off\nbacktrace\nquit\n" > $gdbcommandfile
ulimit -c unlimited
"$@"&
pid=$!
wait $!
if [[ $? -eq 139 ]]; then
    if [[ $usepid == 1 ]]; then 
        gdb -q $1 core.$pid -x $gdbcommandfile
    else
        gdb -q $1 core -x $gdbcommandfile
    fi
fi
rm $gdbcommandfile
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