sigtrap.pm revision 1.1 
1package sigtrap;
2
3=head1 NAME
4
5sigtrap - Perl pragma to enable stack backtrace on unexpected signals
6
7=head1 SYNOPSIS
8
9    use sigtrap;
10    use sigtrap qw(BUS SEGV PIPE SYS ABRT TRAP);
11
12=head1 DESCRIPTION
13
14The C<sigtrap> pragma initializes some default signal handlers that print
15a stack dump of your Perl program, then sends itself a SIGABRT.  This
16provides a nice starting point if something horrible goes wrong.
17
18By default, handlers are installed for the ABRT, BUS, EMT, FPE, ILL, PIPE,
19QUIT, SEGV, SYS, TERM, and TRAP signals.
20
21See L<perlmod/Pragmatic Modules>.
22
23=cut
24
25require Carp;
26
27sub import {
28    my $pack = shift;
29    my @sigs = @_;
30    @sigs or @sigs = qw(QUIT ILL TRAP ABRT EMT FPE BUS SEGV SYS PIPE TERM);
31    foreach $sig (@sigs) {
32	$SIG{$sig} = 'sigtrap::trap';
33    }
34}
35
36sub trap {
37    package DB;		# To get subroutine args.
38    $SIG{'ABRT'} = DEFAULT;
39    kill 'ABRT', $$ if $panic++;
40    syswrite(STDERR, 'Caught a SIG', 12);
41    syswrite(STDERR, $_[0], length($_[0]));
42    syswrite(STDERR, ' at ', 4);
43    ($pack,$file,$line) = caller;
44    syswrite(STDERR, $file, length($file));
45    syswrite(STDERR, ' line ', 6);
46    syswrite(STDERR, $line, length($line));
47    syswrite(STDERR, "\n", 1);
48
49    # Now go for broke.
50    for ($i = 1; ($p,$f,$l,$s,$h,$w,$e,$r) = caller($i); $i++) {
51        @a = ();
52	for $arg (@args) {
53	    $_ = "$arg";
54	    s/([\'\\])/\\$1/g;
55	    s/([^\0]*)/'$1'/
56	      unless /^(?: -?[\d.]+ | \*[\w:]* )$/x;
57	    s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg;
58	    s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg;
59	    push(@a, $_);
60	}
61	$w = $w ? '@ = ' : '$ = ';
62	$a = $h ? '(' . join(', ', @a) . ')' : '';
63	$e =~ s/\n\s*\;\s*\Z// if $e;
64	$e =~ s/[\\\']/\\$1/g if $e;
65	if ($r) {
66	    $s = "require '$e'";
67	} elsif (defined $r) {
68	    $s = "eval '$e'";
69	} elsif ($s eq '(eval)') {
70	    $s = "eval {...}";
71	}
72	$f = "file `$f'" unless $f eq '-e';
73	$mess = "$w$s$a called from $f line $l\n";
74	syswrite(STDERR, $mess, length($mess));
75    }
76    kill 'ABRT', $$;
77}
78
791;
80