Merge branch 'sd/stash-wo-user-name'
[git/raj.git] / perl / FromCPAN / Error.pm
blob8b95e2d73d0f8f8d5b50eaaa360135f102b52b74
1 # Error.pm
3 # Copyright (c) 1997-8 Graham Barr <gbarr@ti.com>. All rights reserved.
4 # This program is free software; you can redistribute it and/or
5 # modify it under the same terms as Perl itself.
7 # Based on my original Error.pm, and Exceptions.pm by Peter Seibel
8 # <peter@weblogic.com> and adapted by Jesse Glick <jglick@sig.bsh.com>.
10 # but modified ***significantly***
12 package Error;
14 use strict;
15 use warnings;
17 use vars qw($VERSION);
18 use 5.004;
20 $VERSION = "0.17025";
22 use overload (
23 '""' => 'stringify',
24 '0+' => 'value',
25 'bool' => sub { return 1; },
26 'fallback' => 1
29 $Error::Depth = 0; # Depth to pass to caller()
30 $Error::Debug = 0; # Generate verbose stack traces
31 @Error::STACK = (); # Clause stack for try
32 $Error::THROWN = undef; # last error thrown, a workaround until die $ref works
34 my $LAST; # Last error created
35 my %ERROR; # Last error associated with package
37 sub _throw_Error_Simple
39 my $args = shift;
40 return Error::Simple->new($args->{'text'});
43 $Error::ObjectifyCallback = \&_throw_Error_Simple;
46 # Exported subs are defined in Error::subs
48 use Scalar::Util ();
50 sub import {
51 shift;
52 my @tags = @_;
53 local $Exporter::ExportLevel = $Exporter::ExportLevel + 1;
55 @tags = grep {
56 if( $_ eq ':warndie' ) {
57 Error::WarnDie->import();
60 else {
63 } @tags;
65 Error::subs->import(@tags);
68 # I really want to use last for the name of this method, but it is a keyword
69 # which prevent the syntax last Error
71 sub prior {
72 shift; # ignore
74 return $LAST unless @_;
76 my $pkg = shift;
77 return exists $ERROR{$pkg} ? $ERROR{$pkg} : undef
78 unless ref($pkg);
80 my $obj = $pkg;
81 my $err = undef;
82 if($obj->isa('HASH')) {
83 $err = $obj->{'__Error__'}
84 if exists $obj->{'__Error__'};
86 elsif($obj->isa('GLOB')) {
87 $err = ${*$obj}{'__Error__'}
88 if exists ${*$obj}{'__Error__'};
91 $err;
94 sub flush {
95 shift; #ignore
97 unless (@_) {
98 $LAST = undef;
99 return;
102 my $pkg = shift;
103 return unless ref($pkg);
105 undef $ERROR{$pkg} if defined $ERROR{$pkg};
108 # Return as much information as possible about where the error
109 # happened. The -stacktrace element only exists if $Error::DEBUG
110 # was set when the error was created
112 sub stacktrace {
113 my $self = shift;
115 return $self->{'-stacktrace'}
116 if exists $self->{'-stacktrace'};
118 my $text = exists $self->{'-text'} ? $self->{'-text'} : "Died";
120 $text .= sprintf(" at %s line %d.\n", $self->file, $self->line)
121 unless($text =~ /\n$/s);
123 $text;
127 sub associate {
128 my $err = shift;
129 my $obj = shift;
131 return unless ref($obj);
133 if($obj->isa('HASH')) {
134 $obj->{'__Error__'} = $err;
136 elsif($obj->isa('GLOB')) {
137 ${*$obj}{'__Error__'} = $err;
139 $obj = ref($obj);
140 $ERROR{ ref($obj) } = $err;
142 return;
146 sub new {
147 my $self = shift;
148 my($pkg,$file,$line) = caller($Error::Depth);
150 my $err = bless {
151 '-package' => $pkg,
152 '-file' => $file,
153 '-line' => $line,
155 }, $self;
157 $err->associate($err->{'-object'})
158 if(exists $err->{'-object'});
160 # To always create a stacktrace would be very inefficient, so
161 # we only do it if $Error::Debug is set
163 if($Error::Debug) {
164 require Carp;
165 local $Carp::CarpLevel = $Error::Depth;
166 my $text = defined($err->{'-text'}) ? $err->{'-text'} : "Error";
167 my $trace = Carp::longmess($text);
168 # Remove try calls from the trace
169 $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
170 $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::run_clauses[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
171 $err->{'-stacktrace'} = $trace
174 $@ = $LAST = $ERROR{$pkg} = $err;
177 # Throw an error. this contains some very gory code.
179 sub throw {
180 my $self = shift;
181 local $Error::Depth = $Error::Depth + 1;
183 # if we are not rethrow-ing then create the object to throw
184 $self = $self->new(@_) unless ref($self);
186 die $Error::THROWN = $self;
189 # syntactic sugar for
191 # die with Error( ... );
193 sub with {
194 my $self = shift;
195 local $Error::Depth = $Error::Depth + 1;
197 $self->new(@_);
200 # syntactic sugar for
202 # record Error( ... ) and return;
204 sub record {
205 my $self = shift;
206 local $Error::Depth = $Error::Depth + 1;
208 $self->new(@_);
211 # catch clause for
213 # try { ... } catch CLASS with { ... }
215 sub catch {
216 my $pkg = shift;
217 my $code = shift;
218 my $clauses = shift || {};
219 my $catch = $clauses->{'catch'} ||= [];
221 unshift @$catch, $pkg, $code;
223 $clauses;
226 # Object query methods
228 sub object {
229 my $self = shift;
230 exists $self->{'-object'} ? $self->{'-object'} : undef;
233 sub file {
234 my $self = shift;
235 exists $self->{'-file'} ? $self->{'-file'} : undef;
238 sub line {
239 my $self = shift;
240 exists $self->{'-line'} ? $self->{'-line'} : undef;
243 sub text {
244 my $self = shift;
245 exists $self->{'-text'} ? $self->{'-text'} : undef;
248 # overload methods
250 sub stringify {
251 my $self = shift;
252 defined $self->{'-text'} ? $self->{'-text'} : "Died";
255 sub value {
256 my $self = shift;
257 exists $self->{'-value'} ? $self->{'-value'} : undef;
260 package Error::Simple;
262 use vars qw($VERSION);
264 $VERSION = "0.17025";
266 @Error::Simple::ISA = qw(Error);
268 sub new {
269 my $self = shift;
270 my $text = "" . shift;
271 my $value = shift;
272 my(@args) = ();
274 local $Error::Depth = $Error::Depth + 1;
276 @args = ( -file => $1, -line => $2)
277 if($text =~ s/\s+at\s+(\S+)\s+line\s+(\d+)(?:,\s*<[^>]*>\s+line\s+\d+)?\.?\n?$//s);
278 push(@args, '-value', 0 + $value)
279 if defined($value);
281 $self->SUPER::new(-text => $text, @args);
284 sub stringify {
285 my $self = shift;
286 my $text = $self->SUPER::stringify;
287 $text .= sprintf(" at %s line %d.\n", $self->file, $self->line)
288 unless($text =~ /\n$/s);
289 $text;
292 ##########################################################################
293 ##########################################################################
295 # Inspired by code from Jesse Glick <jglick@sig.bsh.com> and
296 # Peter Seibel <peter@weblogic.com>
298 package Error::subs;
300 use Exporter ();
301 use vars qw(@EXPORT_OK @ISA %EXPORT_TAGS);
303 @EXPORT_OK = qw(try with finally except otherwise);
304 %EXPORT_TAGS = (try => \@EXPORT_OK);
306 @ISA = qw(Exporter);
308 sub run_clauses ($$$\@) {
309 my($clauses,$err,$wantarray,$result) = @_;
310 my $code = undef;
312 $err = $Error::ObjectifyCallback->({'text' =>$err}) unless ref($err);
314 CATCH: {
316 # catch
317 my $catch;
318 if(defined($catch = $clauses->{'catch'})) {
319 my $i = 0;
321 CATCHLOOP:
322 for( ; $i < @$catch ; $i += 2) {
323 my $pkg = $catch->[$i];
324 unless(defined $pkg) {
325 #except
326 splice(@$catch,$i,2,$catch->[$i+1]->($err));
327 $i -= 2;
328 next CATCHLOOP;
330 elsif(Scalar::Util::blessed($err) && $err->isa($pkg)) {
331 $code = $catch->[$i+1];
332 while(1) {
333 my $more = 0;
334 local($Error::THROWN, $@);
335 my $ok = eval {
336 $@ = $err;
337 if($wantarray) {
338 @{$result} = $code->($err,\$more);
340 elsif(defined($wantarray)) {
341 @{$result} = ();
342 $result->[0] = $code->($err,\$more);
344 else {
345 $code->($err,\$more);
349 if( $ok ) {
350 next CATCHLOOP if $more;
351 undef $err;
353 else {
354 $err = $@ || $Error::THROWN;
355 $err = $Error::ObjectifyCallback->({'text' =>$err})
356 unless ref($err);
358 last CATCH;
364 # otherwise
365 my $owise;
366 if(defined($owise = $clauses->{'otherwise'})) {
367 my $code = $clauses->{'otherwise'};
368 my $more = 0;
369 local($Error::THROWN, $@);
370 my $ok = eval {
371 $@ = $err;
372 if($wantarray) {
373 @{$result} = $code->($err,\$more);
375 elsif(defined($wantarray)) {
376 @{$result} = ();
377 $result->[0] = $code->($err,\$more);
379 else {
380 $code->($err,\$more);
384 if( $ok ) {
385 undef $err;
387 else {
388 $err = $@ || $Error::THROWN;
390 $err = $Error::ObjectifyCallback->({'text' =>$err})
391 unless ref($err);
395 $err;
398 sub try (&;$) {
399 my $try = shift;
400 my $clauses = @_ ? shift : {};
401 my $ok = 0;
402 my $err = undef;
403 my @result = ();
405 unshift @Error::STACK, $clauses;
407 my $wantarray = wantarray();
409 do {
410 local $Error::THROWN = undef;
411 local $@ = undef;
413 $ok = eval {
414 if($wantarray) {
415 @result = $try->();
417 elsif(defined $wantarray) {
418 $result[0] = $try->();
420 else {
421 $try->();
426 $err = $@ || $Error::THROWN
427 unless $ok;
430 shift @Error::STACK;
432 $err = run_clauses($clauses,$err,wantarray,@result)
433 unless($ok);
435 $clauses->{'finally'}->()
436 if(defined($clauses->{'finally'}));
438 if (defined($err))
440 if (Scalar::Util::blessed($err) && $err->can('throw'))
442 throw $err;
444 else
446 die $err;
450 wantarray ? @result : $result[0];
453 # Each clause adds a sub to the list of clauses. The finally clause is
454 # always the last, and the otherwise clause is always added just before
455 # the finally clause.
457 # All clauses, except the finally clause, add a sub which takes one argument
458 # this argument will be the error being thrown. The sub will return a code ref
459 # if that clause can handle that error, otherwise undef is returned.
461 # The otherwise clause adds a sub which unconditionally returns the users
462 # code reference, this is why it is forced to be last.
464 # The catch clause is defined in Error.pm, as the syntax causes it to
465 # be called as a method
467 sub with (&;$) {
471 sub finally (&) {
472 my $code = shift;
473 my $clauses = { 'finally' => $code };
474 $clauses;
477 # The except clause is a block which returns a hashref or a list of
478 # key-value pairs, where the keys are the classes and the values are subs.
480 sub except (&;$) {
481 my $code = shift;
482 my $clauses = shift || {};
483 my $catch = $clauses->{'catch'} ||= [];
485 my $sub = sub {
486 my $ref;
487 my(@array) = $code->($_[0]);
488 if(@array == 1 && ref($array[0])) {
489 $ref = $array[0];
490 $ref = [ %$ref ]
491 if(UNIVERSAL::isa($ref,'HASH'));
493 else {
494 $ref = \@array;
496 @$ref
499 unshift @{$catch}, undef, $sub;
501 $clauses;
504 sub otherwise (&;$) {
505 my $code = shift;
506 my $clauses = shift || {};
508 if(exists $clauses->{'otherwise'}) {
509 require Carp;
510 Carp::croak("Multiple otherwise clauses");
513 $clauses->{'otherwise'} = $code;
515 $clauses;
520 package Error::WarnDie;
522 sub gen_callstack($)
524 my ( $start ) = @_;
526 require Carp;
527 local $Carp::CarpLevel = $start;
528 my $trace = Carp::longmess("");
529 # Remove try calls from the trace
530 $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
531 $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::run_clauses[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
532 my @callstack = split( m/\n/, $trace );
533 return @callstack;
536 my $old_DIE;
537 my $old_WARN;
539 sub DEATH
541 my ( $e ) = @_;
543 local $SIG{__DIE__} = $old_DIE if( defined $old_DIE );
545 die @_ if $^S;
547 my ( $etype, $message, $location, @callstack );
548 if ( ref($e) && $e->isa( "Error" ) ) {
549 $etype = "exception of type " . ref( $e );
550 $message = $e->text;
551 $location = $e->file . ":" . $e->line;
552 @callstack = split( m/\n/, $e->stacktrace );
554 else {
555 # Don't apply subsequent layer of message formatting
556 die $e if( $e =~ m/^\nUnhandled perl error caught at toplevel:\n\n/ );
557 $etype = "perl error";
558 my $stackdepth = 0;
559 while( caller( $stackdepth ) =~ m/^Error(?:$|::)/ ) {
560 $stackdepth++
563 @callstack = gen_callstack( $stackdepth + 1 );
565 $message = "$e";
566 chomp $message;
568 if ( $message =~ s/ at (.*?) line (\d+)\.$// ) {
569 $location = $1 . ":" . $2;
571 else {
572 my @caller = caller( $stackdepth );
573 $location = $caller[1] . ":" . $caller[2];
577 shift @callstack;
578 # Do it this way in case there are no elements; we don't print a spurious \n
579 my $callstack = join( "", map { "$_\n"} @callstack );
581 die "\nUnhandled $etype caught at toplevel:\n\n $message\n\nThrown from: $location\n\nFull stack trace:\n\n$callstack\n";
584 sub TAXES
586 my ( $message ) = @_;
588 local $SIG{__WARN__} = $old_WARN if( defined $old_WARN );
590 $message =~ s/ at .*? line \d+\.$//;
591 chomp $message;
593 my @callstack = gen_callstack( 1 );
594 my $location = shift @callstack;
596 # $location already starts in a leading space
597 $message .= $location;
599 # Do it this way in case there are no elements; we don't print a spurious \n
600 my $callstack = join( "", map { "$_\n"} @callstack );
602 warn "$message:\n$callstack";
605 sub import
607 $old_DIE = $SIG{__DIE__};
608 $old_WARN = $SIG{__WARN__};
610 $SIG{__DIE__} = \&DEATH;
611 $SIG{__WARN__} = \&TAXES;
616 __END__
618 =head1 NAME
620 Error - Error/exception handling in an OO-ish way
622 =head1 WARNING
624 Using the "Error" module is B<no longer recommended> due to the black-magical
625 nature of its syntactic sugar, which often tends to break. Its maintainers
626 have stopped actively writing code that uses it, and discourage people
627 from doing so. See the "SEE ALSO" section below for better recommendations.
629 =head1 SYNOPSIS
631 use Error qw(:try);
633 throw Error::Simple( "A simple error");
635 sub xyz {
637 record Error::Simple("A simple error")
638 and return;
641 unlink($file) or throw Error::Simple("$file: $!",$!);
643 try {
644 do_some_stuff();
645 die "error!" if $condition;
646 throw Error::Simple "Oops!" if $other_condition;
648 catch Error::IO with {
649 my $E = shift;
650 print STDERR "File ", $E->{'-file'}, " had a problem\n";
652 except {
653 my $E = shift;
654 my $general_handler=sub {send_message $E->{-description}};
655 return {
656 UserException1 => $general_handler,
657 UserException2 => $general_handler
660 otherwise {
661 print STDERR "Well I don't know what to say\n";
663 finally {
664 close_the_garage_door_already(); # Should be reliable
665 }; # Don't forget the trailing ; or you might be surprised
667 =head1 DESCRIPTION
669 The C<Error> package provides two interfaces. Firstly C<Error> provides
670 a procedural interface to exception handling. Secondly C<Error> is a
671 base class for errors/exceptions that can either be thrown, for
672 subsequent catch, or can simply be recorded.
674 Errors in the class C<Error> should not be thrown directly, but the
675 user should throw errors from a sub-class of C<Error>.
677 =head1 PROCEDURAL INTERFACE
679 C<Error> exports subroutines to perform exception handling. These will
680 be exported if the C<:try> tag is used in the C<use> line.
682 =over 4
684 =item try BLOCK CLAUSES
686 C<try> is the main subroutine called by the user. All other subroutines
687 exported are clauses to the try subroutine.
689 The BLOCK will be evaluated and, if no error is throw, try will return
690 the result of the block.
692 C<CLAUSES> are the subroutines below, which describe what to do in the
693 event of an error being thrown within BLOCK.
695 =item catch CLASS with BLOCK
697 This clauses will cause all errors that satisfy C<$err-E<gt>isa(CLASS)>
698 to be caught and handled by evaluating C<BLOCK>.
700 C<BLOCK> will be passed two arguments. The first will be the error
701 being thrown. The second is a reference to a scalar variable. If this
702 variable is set by the catch block then, on return from the catch
703 block, try will continue processing as if the catch block was never
704 found. The error will also be available in C<$@>.
706 To propagate the error the catch block may call C<$err-E<gt>throw>
708 If the scalar reference by the second argument is not set, and the
709 error is not thrown. Then the current try block will return with the
710 result from the catch block.
712 =item except BLOCK
714 When C<try> is looking for a handler, if an except clause is found
715 C<BLOCK> is evaluated. The return value from this block should be a
716 HASHREF or a list of key-value pairs, where the keys are class names
717 and the values are CODE references for the handler of errors of that
718 type.
720 =item otherwise BLOCK
722 Catch any error by executing the code in C<BLOCK>
724 When evaluated C<BLOCK> will be passed one argument, which will be the
725 error being processed. The error will also be available in C<$@>.
727 Only one otherwise block may be specified per try block
729 =item finally BLOCK
731 Execute the code in C<BLOCK> either after the code in the try block has
732 successfully completed, or if the try block throws an error then
733 C<BLOCK> will be executed after the handler has completed.
735 If the handler throws an error then the error will be caught, the
736 finally block will be executed and the error will be re-thrown.
738 Only one finally block may be specified per try block
740 =back
742 =head1 COMPATIBILITY
744 L<Moose> exports a keyword called C<with> which clashes with Error's. This
745 example returns a prototype mismatch error:
747 package MyTest;
749 use warnings;
750 use Moose;
751 use Error qw(:try);
753 (Thanks to C<maik.hentsche@amd.com> for the report.).
755 =head1 CLASS INTERFACE
757 =head2 CONSTRUCTORS
759 The C<Error> object is implemented as a HASH. This HASH is initialized
760 with the arguments that are passed to it's constructor. The elements
761 that are used by, or are retrievable by the C<Error> class are listed
762 below, other classes may add to these.
764 -file
765 -line
766 -text
767 -value
768 -object
770 If C<-file> or C<-line> are not specified in the constructor arguments
771 then these will be initialized with the file name and line number where
772 the constructor was called from.
774 If the error is associated with an object then the object should be
775 passed as the C<-object> argument. This will allow the C<Error> package
776 to associate the error with the object.
778 The C<Error> package remembers the last error created, and also the
779 last error associated with a package. This could either be the last
780 error created by a sub in that package, or the last error which passed
781 an object blessed into that package as the C<-object> argument.
783 =over 4
785 =item Error->new()
787 See the Error::Simple documentation.
789 =item throw ( [ ARGS ] )
791 Create a new C<Error> object and throw an error, which will be caught
792 by a surrounding C<try> block, if there is one. Otherwise it will cause
793 the program to exit.
795 C<throw> may also be called on an existing error to re-throw it.
797 =item with ( [ ARGS ] )
799 Create a new C<Error> object and returns it. This is defined for
800 syntactic sugar, eg
802 die with Some::Error ( ... );
804 =item record ( [ ARGS ] )
806 Create a new C<Error> object and returns it. This is defined for
807 syntactic sugar, eg
809 record Some::Error ( ... )
810 and return;
812 =back
814 =head2 STATIC METHODS
816 =over 4
818 =item prior ( [ PACKAGE ] )
820 Return the last error created, or the last error associated with
821 C<PACKAGE>
823 =item flush ( [ PACKAGE ] )
825 Flush the last error created, or the last error associated with
826 C<PACKAGE>.It is necessary to clear the error stack before exiting the
827 package or uncaught errors generated using C<record> will be reported.
829 $Error->flush;
831 =cut
833 =back
835 =head2 OBJECT METHODS
837 =over 4
839 =item stacktrace
841 If the variable C<$Error::Debug> was non-zero when the error was
842 created, then C<stacktrace> returns a string created by calling
843 C<Carp::longmess>. If the variable was zero the C<stacktrace> returns
844 the text of the error appended with the filename and line number of
845 where the error was created, providing the text does not end with a
846 newline.
848 =item object
850 The object this error was associated with
852 =item file
854 The file where the constructor of this error was called from
856 =item line
858 The line where the constructor of this error was called from
860 =item text
862 The text of the error
864 =item $err->associate($obj)
866 Associates an error with an object to allow error propagation. I.e:
868 $ber->encode(...) or
869 return Error->prior($ber)->associate($ldap);
871 =back
873 =head2 OVERLOAD METHODS
875 =over 4
877 =item stringify
879 A method that converts the object into a string. This method may simply
880 return the same as the C<text> method, or it may append more
881 information. For example the file name and line number.
883 By default this method returns the C<-text> argument that was passed to
884 the constructor, or the string C<"Died"> if none was given.
886 =item value
888 A method that will return a value that can be associated with the
889 error. For example if an error was created due to the failure of a
890 system call, then this may return the numeric value of C<$!> at the
891 time.
893 By default this method returns the C<-value> argument that was passed
894 to the constructor.
896 =back
898 =head1 PRE-DEFINED ERROR CLASSES
900 =head2 Error::Simple
902 This class can be used to hold simple error strings and values. It's
903 constructor takes two arguments. The first is a text value, the second
904 is a numeric value. These values are what will be returned by the
905 overload methods.
907 If the text value ends with C<at file line 1> as $@ strings do, then
908 this information will be used to set the C<-file> and C<-line> arguments
909 of the error object.
911 This class is used internally if an eval'd block die's with an error
912 that is a plain string. (Unless C<$Error::ObjectifyCallback> is modified)
915 =head1 $Error::ObjectifyCallback
917 This variable holds a reference to a subroutine that converts errors that
918 are plain strings to objects. It is used by Error.pm to convert textual
919 errors to objects, and can be overridden by the user.
921 It accepts a single argument which is a hash reference to named parameters.
922 Currently the only named parameter passed is C<'text'> which is the text
923 of the error, but others may be available in the future.
925 For example the following code will cause Error.pm to throw objects of the
926 class MyError::Bar by default:
928 sub throw_MyError_Bar
930 my $args = shift;
931 my $err = MyError::Bar->new();
932 $err->{'MyBarText'} = $args->{'text'};
933 return $err;
937 local $Error::ObjectifyCallback = \&throw_MyError_Bar;
939 # Error handling here.
942 =cut
944 =head1 MESSAGE HANDLERS
946 C<Error> also provides handlers to extend the output of the C<warn()> perl
947 function, and to handle the printing of a thrown C<Error> that is not caught
948 or otherwise handled. These are not installed by default, but are requested
949 using the C<:warndie> tag in the C<use> line.
951 use Error qw( :warndie );
953 These new error handlers are installed in C<$SIG{__WARN__}> and
954 C<$SIG{__DIE__}>. If these handlers are already defined when the tag is
955 imported, the old values are stored, and used during the new code. Thus, to
956 arrange for custom handling of warnings and errors, you will need to perform
957 something like the following:
959 BEGIN {
960 $SIG{__WARN__} = sub {
961 print STDERR "My special warning handler: $_[0]"
965 use Error qw( :warndie );
967 Note that setting C<$SIG{__WARN__}> after the C<:warndie> tag has been
968 imported will overwrite the handler that C<Error> provides. If this cannot be
969 avoided, then the tag can be explicitly C<import>ed later
971 use Error;
973 $SIG{__WARN__} = ...;
975 import Error qw( :warndie );
977 =head2 EXAMPLE
979 The C<__DIE__> handler turns messages such as
981 Can't call method "foo" on an undefined value at examples/warndie.pl line 16.
983 into
985 Unhandled perl error caught at toplevel:
987 Can't call method "foo" on an undefined value
989 Thrown from: examples/warndie.pl:16
991 Full stack trace:
993 main::inner('undef') called at examples/warndie.pl line 20
994 main::outer('undef') called at examples/warndie.pl line 23
996 =cut
998 =head1 SEE ALSO
1000 See L<Exception::Class> for a different module providing Object-Oriented
1001 exception handling, along with a convenient syntax for declaring hierarchies
1002 for them. It doesn't provide Error's syntactic sugar of C<try { ... }>,
1003 C<catch { ... }>, etc. which may be a good thing or a bad thing based
1004 on what you want. (Because Error's syntactic sugar tends to break.)
1006 L<Error::Exception> aims to combine L<Error> and L<Exception::Class>
1007 "with correct stringification".
1009 L<TryCatch> and L<Try::Tiny> are similar in concept to Error.pm only providing
1010 a syntax that hopefully breaks less.
1012 =head1 KNOWN BUGS
1014 None, but that does not mean there are not any.
1016 =head1 AUTHORS
1018 Graham Barr <gbarr@pobox.com>
1020 The code that inspired me to write this was originally written by
1021 Peter Seibel <peter@weblogic.com> and adapted by Jesse Glick
1022 <jglick@sig.bsh.com>.
1024 C<:warndie> handlers added by Paul Evans <leonerd@leonerd.org.uk>
1026 =head1 MAINTAINER
1028 Shlomi Fish, L<http://www.shlomifish.org/> .
1030 =head1 PAST MAINTAINERS
1032 Arun Kumar U <u_arunkumar@yahoo.com>
1034 =head1 COPYRIGHT
1036 Copyright (c) 1997-8 Graham Barr. All rights reserved.
1037 This program is free software; you can redistribute it and/or modify it
1038 under the same terms as Perl itself.
1040 =cut