package sigtrap;
=head1 NAME
sigtrap - Perl pragma to enable simple signal handling
=cut
use Carp;
$VERSION = 1.09;
$Verbose ||= 0;
sub import {
my $pkg = shift;
my $handler = \&handler_traceback;
my $saw_sig = 0;
my $untrapped = 0;
local $_;
Arg_loop:
while (@_) {
$_ = shift;
if (/^[A-Z][A-Z0-9]*$/) {
$saw_sig++;
unless ($untrapped and $SIG{$_} and $SIG{$_} ne 'DEFAULT') {
print "Installing handler $handler for $_\n" if $Verbose;
$SIG{$_} = $handler;
}
}
elsif ($_ eq 'normal-signals') {
unshift @_, grep(exists $SIG{$_}, qw(HUP INT PIPE TERM));
}
elsif ($_ eq 'error-signals') {
unshift @_, grep(exists $SIG{$_},
qw(ABRT BUS EMT FPE ILL QUIT SEGV SYS TRAP));
}
elsif ($_ eq 'old-interface-signals') {
unshift @_,
grep(exists $SIG{$_},
qw(ABRT BUS EMT FPE ILL PIPE QUIT SEGV SYS TERM TRAP));
}
elsif ($_ eq 'stack-trace') {
$handler = \&handler_traceback;
}
elsif ($_ eq 'die') {
$handler = \&handler_die;
}
elsif ($_ eq 'handler') {
@_ or croak "No argument specified after 'handler'";
$handler = shift;
unless (ref $handler or $handler eq 'IGNORE'
or $handler eq 'DEFAULT') {
require Symbol;
$handler = Symbol::qualify($handler, (caller)[0]);
}
}
elsif ($_ eq 'untrapped') {
$untrapped = 1;
}
elsif ($_ eq 'any') {
$untrapped = 0;
}
elsif ($_ =~ /^\d/) {
$VERSION >= $_ or croak "sigtrap.pm version $_ required,"
. " but this is only version $VERSION";
}
else {
croak "Unrecognized argument $_";
}
}
unless ($saw_sig) {
@_ = qw(old-interface-signals);
goto Arg_loop;
}
}
sub handler_die {
croak "Caught a SIG$_[0]";
}
sub handler_traceback {
package DB; # To get subroutine args.
my $use_print;
$SIG{'ABRT'} = DEFAULT;
kill 'ABRT', $$ if $panic++;
# This function might be called as an unsafe signal handler, so it
# tries to delay any memory allocations as long as possible.
#
# Unfortunately with PerlIO layers, using syswrite() here has always
# been broken.
#
# Calling PerlIO::get_layers() here is tempting, but that does
# allocations, which we're trying to avoid for this early code.
if (eval { syswrite(STDERR, 'Caught a SIG', 12); 1 }) {
syswrite(STDERR, $_[0], length($_[0]));
syswrite(STDERR, ' at ', 4);
}
else {
print STDERR 'Caught a SIG', $_[0], ' at ';
++$use_print;
}
($pack,$file,$line) = caller;
unless ($use_print) {
syswrite(STDERR, $file, length($file));
syswrite(STDERR, ' line ', 6);
syswrite(STDERR, $line, length($line));
syswrite(STDERR, "\n", 1);
}
else {
print STDERR $file, ' line ', $line, "\n";
}
# we've got our basic output done, from now on we can be freer with allocations
# find out whether we have any layers we need to worry about
unless ($use_print) {
my @layers = PerlIO::get_layers(*STDERR);
for my $name (@layers) {
unless ($name =~ /^(unix|perlio)$/) {
++$use_print;
last;
}
}
}
# Now go for broke.
for ($i = 1; ($p,$f,$l,$s,$h,$w,$e,$r) = caller($i); $i++) {
@a = ();
for (@{[@args]}) {
s/([\'\\])/\\$1/g;
s/([^\0]*)/'$1'/
unless /^(?: -?[\d.]+ | \*[\w:]* )$/x;
require 'meta_notation.pm';
$_ = _meta_notation($_) if /[[:^print:]]/a;
push(@a, $_);
}
$w = $w ? '@ = ' : '$ = ';
$a = $h ? '(' . join(', ', @a) . ')' : '';
$e =~ s/\n\s*\;\s*\Z// if $e;
$e =~ s/[\\\']/\\$1/g if $e;
if ($r) {
$s = "require '$e'";
} elsif (defined $r) {
$s = "eval '$e'";
} elsif ($s eq '(eval)') {
$s = "eval {...}";
}
$f = "file '$f'" unless $f eq '-e';
$mess = "$w$s$a called from $f line $l\n";
if ($use_print) {
print STDERR $mess;
}
else {
syswrite(STDERR, $mess, length($mess));
}
}
kill 'ABRT', $$;
}
1;
__END__
=head1 SYNOPSIS
use sigtrap;
use sigtrap qw(stack-trace old-interface-signals); # equivalent
use sigtrap qw(BUS SEGV PIPE ABRT);
use sigtrap qw(die INT QUIT);
use sigtrap qw(die normal-signals);
use sigtrap qw(die untrapped normal-signals);
use sigtrap qw(die untrapped normal-signals
stack-trace any error-signals);
use sigtrap 'handler' => \&my_handler, 'normal-signals';
use sigtrap qw(handler my_handler normal-signals
stack-trace error-signals);
=head1 DESCRIPTION
The B<sigtrap> pragma is a simple interface to installing signal
handlers. You can have it install one of two handlers supplied by
B<sigtrap> itself (one which provides a Perl stack trace and one which
simply C<die()>s), or alternately you can supply your own handler for it
to install. It can be told only to install a handler for signals which
are either untrapped or ignored. It has a couple of lists of signals to
trap, plus you can supply your own list of signals.
The arguments passed to the C<use> statement which invokes B<sigtrap>
are processed in order. When a signal name or the name of one of
B<sigtrap>'s signal lists is encountered a handler is immediately
installed, when an option is encountered it affects subsequently
installed handlers.
=head1 OPTIONS
=head2 SIGNAL HANDLERS
These options affect which handler will be used for subsequently
installed signals.
=over 4
=item B<stack-trace>
The handler used for subsequently installed signals outputs a Perl stack
trace to STDERR and then tries to dump core. This is the default signal
handler.
=item B<die>
The handler used for subsequently installed signals calls C<die>
(actually C<croak>) with a message indicating which signal was caught.
=item B<handler> I<your-handler>
I<your-handler> will be used as the handler for subsequently installed
signals. I<your-handler> can be any value which is valid as an
assignment to an element of C<%SIG>. See L<perlvar> for examples of
handler functions.
=back
=head2 SIGNAL LISTS
B<sigtrap> has a few built-in lists of signals to trap. They are:
=over 4
=item B<normal-signals>
These are the signals which a program might normally expect to encounter
and which by default cause it to terminate. They are HUP, INT, PIPE and
TERM.
=item B<error-signals>
These signals usually indicate a serious problem with the Perl
interpreter or with your script. They are ABRT, BUS, EMT, FPE, ILL,
QUIT, SEGV, SYS and TRAP.
=item B<old-interface-signals>
These are the signals which were trapped by default by the old
B<sigtrap> interface, they are ABRT, BUS, EMT, FPE, ILL, PIPE, QUIT,
SEGV, SYS, TERM, and TRAP. If no signals or signals lists are passed to
B<sigtrap>, this list is used.
=back
For each of these three lists, the collection of signals set to be
trapped is checked before trapping; if your architecture does not
implement a particular signal, it will not be trapped but rather
silently ignored.
=head2 OTHER
=over 4
=item B<untrapped>
This token tells B<sigtrap> to install handlers only for subsequently
listed signals which aren't already trapped or ignored.
=item B<any>
This token tells B<sigtrap> to install handlers for all subsequently
listed signals. This is the default behavior.
=item I<signal>
Any argument which looks like a signal name (that is,
C</^[A-Z][A-Z0-9]*$/>) indicates that B<sigtrap> should install a
handler for that name.
=item I<number>
Require that at least version I<number> of B<sigtrap> is being used.
=back
=head1 EXAMPLES
Provide a stack trace for the old-interface-signals:
use sigtrap;
Ditto:
use sigtrap qw(stack-trace old-interface-signals);
Provide a stack trace on the 4 listed signals only:
use sigtrap qw(BUS SEGV PIPE ABRT);
Die on INT or QUIT:
use sigtrap qw(die INT QUIT);
Die on HUP, INT, PIPE or TERM:
use sigtrap qw(die normal-signals);
Die on HUP, INT, PIPE or TERM, except don't change the behavior for
signals which are already trapped or ignored:
use sigtrap qw(die untrapped normal-signals);
Die on receipt one of an of the B<normal-signals> which is currently
B<untrapped>, provide a stack trace on receipt of B<any> of the
B<error-signals>:
use sigtrap qw(die untrapped normal-signals
stack-trace any error-signals);
Install my_handler() as the handler for the B<normal-signals>:
use sigtrap 'handler', \&my_handler, 'normal-signals';
Install my_handler() as the handler for the normal-signals, provide a
Perl stack trace on receipt of one of the error-signals:
use sigtrap qw(handler my_handler normal-signals
stack-trace error-signals);
=cut
