#!/bin/sh
#
# This script uses gdb to grab a stacktrace of the given running process
# or thread.  For a multi-threaded process, use 'ps ax -fL' to get a list
# of all its thread ids that you might want to trace.
#
# Realistically, this script is most useful for a program to call on
# itself upon receiving a signal like SIGSEGV.
#

die()
{
  echo "$@" >&2
  exit 1
}


[ -n "$1" ] || die "Usage: $0 <pid>"
pid=$1
[ -e "/proc/$pid/exe" ] || die "pid invalid: /proc/$pid/exe does not exist"

# need to run gdb on the master process to get backtraces for all threads
line=`grep '^Tgid:' /proc/$pid/status`
tgid=${line##*	}

gdb --batch \
    -ex "set heuristic-fence-post 100000" \
    -ex "thread apply all bt" \
    "/proc/$pid/exe" \
    --pid "$tgid" \
    </dev/null 2>&1 |
(
  echo
  echo '--CRASHDUMP-START--'
  rv=2
  while read level offset in func etc; do
    if [ "$level" = Thread ]; then
      echo "$level $offset $in $func $etc"
    fi
    if [ "$level" != "${level#\#}" ] && [ "$in" = "in" ]; then
      rv=0
      echo "$level $offset $func $etc"
    fi
  done
  echo '--CRASHDUMP-END--'
  echo
  exit $rv
)