sigtrap.pm 7.43 KB
Newer Older
1 2 3 4 5 6 7 8 9 10
package sigtrap;

=head1 NAME

sigtrap - Perl pragma to enable simple signal handling

=cut

use Carp;

11
$VERSION = 1.08;
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97
$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.
    $SIG{'ABRT'} = DEFAULT;
    kill 'ABRT', $$ if $panic++;
    syswrite(STDERR, 'Caught a SIG', 12);
    syswrite(STDERR, $_[0], length($_[0]));
    syswrite(STDERR, ' at ', 4);
    ($pack,$file,$line) = caller;
    syswrite(STDERR, $file, length($file));
    syswrite(STDERR, ' line ', 6);
    syswrite(STDERR, $line, length($line));
    syswrite(STDERR, "\n", 1);

    # Now go for broke.
    for ($i = 1; ($p,$f,$l,$s,$h,$w,$e,$r) = caller($i); $i++) {
        @a = ();
98
	for (@{[@args]}) {
99 100 101
	    s/([\'\\])/\\$1/g;
	    s/([^\0]*)/'$1'/
	      unless /^(?: -?[\d.]+ | \*[\w:]* )$/x;
102 103
            require 'meta_notation.pm';
            $_ = _meta_notation($_) if /[[:^print:]]/a;
104 105 106 107 108 109 110 111 112 113 114 115 116
	    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 {...}";
	}
117
	$f = "file '$f'" unless $f eq '-e';
118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181
	$mess = "$w$s$a called from $f line $l\n";
	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
182 183
assignment to an element of C<%SIG>. See L<perlvar> for examples of
handler functions.
184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289

=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