Greatly expand options for setting handlers

1 files changed, 224 insertions, 24 deletions

diff --git a/lib/sigtrap.pm b/lib/sigtrap.pm
index e099ac4658..f90f46b4ba 100644
--- a/lib/sigtrap.pm
+++ b/lib/sigtrap.pm
@@ -2,38 +2,81 @@ package sigtrap;
 
 =head1 NAME
 
-sigtrap - Perl pragma to enable stack backtrace on unexpected signals
-
-=head1 SYNOPSIS
-
-    use sigtrap;
-    use sigtrap qw(BUS SEGV PIPE SYS ABRT TRAP);
-
-=head1 DESCRIPTION
-
-The C<sigtrap> pragma initializes some default signal handlers that print
-a stack dump of your Perl program, then sends itself a SIGABRT.  This
-provides a nice starting point if something horrible goes wrong.
-
-By default, handlers are installed for the ABRT, BUS, EMT, FPE, ILL, PIPE,
-QUIT, SEGV, SYS, TERM, and TRAP signals.
-
-See L<perlmod/Pragmatic Modules>.
+sigtrap - Perl pragma to enable simple signal handling
 
 =cut
 
-require Carp;
+use Carp;
+
+$VERSION = 1.01;
+$Verbose ||= 0;
 
 sub import {
-    my $pack = shift;
-    my @sigs = @_;
-    @sigs or @sigs = qw(QUIT ILL TRAP ABRT EMT FPE BUS SEGV SYS PIPE TERM);
-    foreach $sig (@sigs) {
-	$SIG{$sig} = 'sigtrap::trap';
+    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 @_, qw(HUP INT PIPE TERM);
+	}
+	elsif ($_ eq 'error-signals') {
+	    unshift @_, qw(ABRT BUS EMT FPE ILL QUIT SEGV SYS TRAP);
+	}
+	elsif ($_ eq 'old-interface-signals') {
+	    unshift @_, 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 trap {
+sub handler_traceback {
     package DB;		# To get subroutine args.
     $SIG{'ABRT'} = DEFAULT;
     kill 'ABRT', $$ if $panic++;
@@ -77,3 +120,160 @@ sub trap {
 }
 
 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
+
+=item B<stack-trace>
+
+The handler used for subsequently installed signals will output 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>.
+
+=back
+
+=head2 SIGNAL LISTS
+
+B<sigtrap> has two built-in lists of signals to trap.  They are:
+
+=over
+
+=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
+
+=head2 OTHER
+
+=item B<untrapped>
+
+This token tells B<sigtrap> only to install handlers 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 signals name (that is,
+C</^[A-Z][A-Z0-9]*$/>) is taken as a signal name and indicates that
+B<sigtrap> should install a handler for it.
+
+=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