eliminate duplicate thread stacks from gdb "thread apply all bt"

gdb.pl

#!/usr/bin/perl -w

use strict;
use Digest::MD5 qw(md5_hex);

my @threads;
my $curr_thd = undef;

$\ = "\n";

LINE:
while (<>) {
  chomp;
  if (/^Thread ([0-9]+) \(Thread 0x[0-9a-f]+ \(LWP [0-9]+\)\):$/) {
    if (defined $curr_thd) {
      $curr_thd->{md5} = md5_hex @{$curr_thd->{frames}};
      push @threads, $curr_thd;
    }
    $curr_thd = {tid => $1, frames => [], text => [$_]};
    next LINE;
  }

  if (/^#[0-9]+\s+(0x[0-9a-f]+ in (void )?)?([a-zA-Z_?:@<>.,*]([a-zA-Z0-9_?:@<>.,*]|\s??)*)\s?\(/) {
    push @{$curr_thd->{text}}, $_;
    push @{$curr_thd->{frames}}, $3;
  }
}
$curr_thd->{md5} = md5_hex @{$curr_thd->{frames}};
push @threads, $curr_thd;

my $printed = {};

for my $thread (@threads) {
  if (exists $printed->{$thread->{md5}}) {
    $printed->{$thread->{md5}}++;
  } else {
    print for (@{$thread->{text}});
    $printed->{$thread->{md5}} = 1;
    print "";
  }
}