11 our $MaxArgLen = 64; # How much of each argument to print. 0 = all.
12 our $MaxArgNums = 8; # How many arguments to print. 0 = all.
15 our @ISA = ('Exporter');
16 our @EXPORT = qw(confess croak carp);
17 our @EXPORT_OK = qw(cluck verbose longmess shortmess);
18 our @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
20 # The members of %Internal are packages that are internal to perl.
21 # Carp will not report errors from within these packages if it
22 # can. The members of %CarpInternal are internal to Perl's warning
23 # system. Carp will not report errors from within these packages
24 # either, and will not report calls *to* these packages for carp and
25 # croak. They replace $CarpLevel, which is deprecated. The
26 # $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
27 # text and function arguments should be formatted when printed.
32 # disable these by default, so they can live w/o require Carp
33 $CarpInternal{Carp}++;
34 $CarpInternal{warnings}++;
35 $Internal{Exporter}++;
36 $Internal{'Exporter::Heavy'}++;
38 # if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
39 # then the following method will be called by the Exporter which knows
40 # to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word
43 sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ }
47 return \&{"CORE::GLOBAL::caller"} if defined &{"CORE::GLOBAL::caller"};
52 # Icky backwards compatibility wrapper. :-(
54 # The story is that the original implementation hard-coded the
55 # number of call levels to go back, so calls to longmess were off
56 # by one. Other code began calling longmess and expecting this
57 # behaviour, so the replacement has to emulate that behaviour.
59 my $call_pack = $cgc ? $cgc->() : caller();
60 if ( $Internal{$call_pack} or $CarpInternal{$call_pack} ) {
61 return longmess_heavy(@_);
64 local $CarpLevel = $CarpLevel + 1;
65 return longmess_heavy(@_);
74 # Icky backwards compatibility wrapper. :-(
75 local @CARP_NOT = $cgc ? $cgc->() : caller();
79 sub croak { die shortmess @_ }
80 sub confess { die longmess @_ }
81 sub carp { warn shortmess @_ }
82 sub cluck { warn longmess @_ }
85 my $i = shift(@_) + 1;
90 @DB::args = \$i; # A sentinel, which no-one else has the address of
92 qw(pack file line sub has_args wantarray evaltext is_require) }
93 = $cgc ? $cgc->($i) : caller($i);
96 unless ( defined $call_info{pack} ) {
100 my $sub_name = Carp::get_subname( \%call_info );
101 if ( $call_info{has_args} ) {
104 && ref $DB::args[0] eq ref \$i
105 && $DB::args[0] == \$i ) {
106 @DB::args = (); # Don't let anyone see the address of $i
109 my $func = $cgc or return '';
112 ( $::{"B::"} || return '') # B stash
113 ->{svref_2object} || return '' # entry in stash
114 }{CODE} # coderef in entry
116 my $package = $gv->STASH->NAME;
117 my $subname = $gv->NAME;
118 return unless defined $package && defined $subname;
120 # returning CORE::GLOBAL::caller isn't useful for tracing the cause:
121 return if $package eq 'CORE::GLOBAL' && $subname eq 'caller';
122 " in &${package}::$subname";
125 = "** Incomplete caller override detected$where; \@DB::args were not set **";
128 @args = map { Carp::format_arg($_) } @DB::args;
130 if ( $MaxArgNums and @args > $MaxArgNums )
131 { # More than we want to show?
132 $#args = $MaxArgNums;
136 # Push the args onto the subroutine
137 $sub_name .= '(' . join( ', ', @args ) . ')';
139 $call_info{sub_name} = $sub_name;
140 return wantarray() ? %call_info : \%call_info;
143 # Transform an argument to a function into a string.
147 $arg = defined($overload::VERSION) ? overload::StrVal($arg) : "$arg";
149 if ( defined($arg) ) {
151 $arg = str_len_trim( $arg, $MaxArgLen );
154 $arg = "'$arg'" unless $arg =~ /^-?[0-9.]+\z/;
155 } # 0-9, not \d, as \d will try to
156 else { # load Unicode tables
160 # The following handling of "control chars" is direct from
161 # the original code - it is broken on Unicode though.
164 or $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;
168 # Takes an inheritance cache and a package and returns
169 # an anon hash of known inheritances and anon array of
170 # inheritances which consequences have not been figured
175 $cache->{$pkg} ||= [ { $pkg => $pkg }, [ trusts_directly($pkg) ] ];
176 return @{ $cache->{$pkg} };
179 # Takes the info from caller() and figures out the name of
180 # the sub/require/eval
183 if ( defined( $info->{evaltext} ) ) {
184 my $eval = $info->{evaltext};
185 if ( $info->{is_require} ) {
186 return "require $eval";
189 $eval =~ s/([\\\'])/\\$1/g;
190 return "eval '" . str_len_trim( $eval, $MaxEvalLen ) . "'";
194 return ( $info->{sub} eq '(eval)' ) ? 'eval {...}' : $info->{sub};
197 # Figures out what call (from the point of view of the caller)
198 # the long error backtrace should start at.
201 my $lvl = $CarpLevel;
205 my $pkg = $cgc ? $cgc->($i) : caller($i);
206 unless ( defined($pkg) ) {
208 # This *shouldn't* happen.
211 $i = long_error_loc();
216 # OK, now I am irritated.
220 redo if $CarpInternal{$pkg};
221 redo unless 0 > --$lvl;
222 redo if $Internal{$pkg};
228 return @_ if ref( $_[0] ); # don't break references as exceptions
229 my $i = long_error_loc();
230 return ret_backtrace( $i, @_ );
233 # Returns a full stack backtrace starting from where it is
236 my ( $i, @error ) = @_;
238 my $err = join '', @error;
242 if ( defined &threads::tid ) {
243 my $tid = threads->tid;
244 $tid_msg = " thread $tid" if $tid;
247 my %i = caller_info($i);
248 $mess = "$err at $i{file} line $i{line}$tid_msg\n";
250 while ( my %i = caller_info( ++$i ) ) {
251 $mess .= "\t$i{sub_name} called at $i{file} line $i{line}$tid_msg\n";
258 my ( $i, @error ) = @_;
259 my $err = join '', @error;
263 if ( defined &threads::tid ) {
264 my $tid = threads->tid;
265 $tid_msg = " thread $tid" if $tid;
268 my %i = caller_info($i);
269 return "$err at $i{file} line $i{line}$tid_msg\n";
272 sub short_error_loc {
273 # You have to create your (hash)ref out here, rather than defaulting it
274 # inside trusts *on a lexical*, as you want it to persist across calls.
275 # (You can default it on $_[2], but that gets messy)
278 my $lvl = $CarpLevel;
281 my $called = $cgc ? $cgc->($i) : caller($i);
283 my $caller = $cgc ? $cgc->($i) : caller($i);
285 return 0 unless defined($caller); # What happened?
286 redo if $Internal{$caller};
287 redo if $CarpInternal{$caller};
288 redo if $CarpInternal{$called};
289 redo if trusts( $called, $caller, $cache );
290 redo if trusts( $caller, $called, $cache );
291 redo unless 0 > --$lvl;
296 sub shortmess_heavy {
297 return longmess_heavy(@_) if $Verbose;
298 return @_ if ref( $_[0] ); # don't break references as exceptions
299 my $i = short_error_loc();
301 ret_summary( $i, @_ );
308 # If a string is too long, trims it with ...
311 my $max = shift || 0;
312 if ( 2 < $max and $max < length($str) ) {
313 substr( $str, $max - 3 ) = '...';
318 # Takes two packages and an optional cache. Says whether the
319 # first inherits from the second.
321 # Recursive versions of this have to work to avoid certain
322 # possible endless loops, and when following long chains of
323 # inheritance are less efficient.
328 my ( $known, $partial ) = get_status( $cache, $child );
330 # Figure out consequences until we have an answer
331 while ( @$partial and not exists $known->{$parent} ) {
332 my $anc = shift @$partial;
333 next if exists $known->{$anc};
335 my ( $anc_knows, $anc_partial ) = get_status( $cache, $anc );
336 my @found = keys %$anc_knows;
337 @$known{@found} = ();
338 push @$partial, @$anc_partial;
340 return exists $known->{$parent};
343 # Takes a package and gives a list of those trusted directly
344 sub trusts_directly {
348 return @{"$class\::CARP_NOT"}
349 ? @{"$class\::CARP_NOT"}
359 Carp - alternative warn and die for modules
365 # warn user (from perspective of caller)
366 carp "string trimmed to 80 chars";
368 # die of errors (from perspective of caller)
369 croak "We're outta here!";
371 # die of errors with stack backtrace
372 confess "not implemented";
374 # cluck not exported by default
376 cluck "This is how we got here!";
380 The Carp routines are useful in your own modules because
381 they act like die() or warn(), but with a message which is more
382 likely to be useful to a user of your module. In the case of
383 cluck, confess, and longmess that context is a summary of every
384 call in the call-stack. For a shorter message you can use C<carp>
385 or C<croak> which report the error as being from where your module
386 was called. There is no guarantee that that is where the error
387 was, but it is a good educated guess.
389 You can also alter the way the output and logic of C<Carp> works, by
390 changing some global variables in the C<Carp> namespace. See the
391 section on C<GLOBAL VARIABLES> below.
393 Here is a more complete description of how C<carp> and C<croak> work.
394 What they do is search the call-stack for a function call stack where
395 they have not been told that there shouldn't be an error. If every
396 call is marked safe, they give up and give a full stack backtrace
397 instead. In other words they presume that the first likely looking
398 potential suspect is guilty. Their rules for telling whether
399 a call shouldn't generate errors work as follows:
405 Any call from a package to itself is safe.
409 Packages claim that there won't be errors on calls to or from
410 packages explicitly marked as safe by inclusion in C<@CARP_NOT>, or
411 (if that array is empty) C<@ISA>. The ability to override what
412 @ISA says is new in 5.8.
416 The trust in item 2 is transitive. If A trusts B, and B
417 trusts C, then A trusts C. So if you do not override C<@ISA>
418 with C<@CARP_NOT>, then this trust relationship is identical to,
423 Any call from an internal Perl module is safe. (Nothing keeps
424 user modules from marking themselves as internal to Perl, but
425 this practice is discouraged.)
429 Any call to Perl's warning system (eg Carp itself) is safe.
430 (This rule is what keeps it from reporting the error at the
431 point where you call C<carp> or C<croak>.)
435 C<$Carp::CarpLevel> can be set to skip a fixed number of additional
436 call levels. Using this is not recommended because it is very
437 difficult to get it to behave correctly.
441 =head2 Forcing a Stack Trace
443 As a debugging aid, you can force Carp to treat a croak as a confess
444 and a carp as a cluck across I<all> modules. In other words, force a
445 detailed stack trace to be given. This can be very helpful when trying
446 to understand why, or from where, a warning or error is being generated.
448 This feature is enabled by 'importing' the non-existent symbol
449 'verbose'. You would typically enable it by saying
451 perl -MCarp=verbose script.pl
453 or by including the string C<-MCarp=verbose> in the PERL5OPT
454 environment variable.
456 Alternately, you can set the global variable C<$Carp::Verbose> to true.
457 See the C<GLOBAL VARIABLES> section below.
459 =head1 GLOBAL VARIABLES
461 =head2 $Carp::MaxEvalLen
463 This variable determines how many characters of a string-eval are to
464 be shown in the output. Use a value of C<0> to show all text.
468 =head2 $Carp::MaxArgLen
470 This variable determines how many characters of each argument to a
471 function to print. Use a value of C<0> to show the full length of the
476 =head2 $Carp::MaxArgNums
478 This variable determines how many arguments to each function to show.
479 Use a value of C<0> to show all arguments to a function call.
483 =head2 $Carp::Verbose
485 This variable makes C<carp> and C<croak> generate stack backtraces
486 just like C<cluck> and C<confess>. This is how C<use Carp 'verbose'>
487 is implemented internally.
493 This variable, I<in your package>, says which packages are I<not> to be
494 considered as the location of an error. The C<carp()> and C<cluck()>
495 functions will skip over callers when reporting where an error occurred.
497 NB: This variable must be in the package's symbol table, thus:
500 our @CARP_NOT; # file scope
501 use vars qw(@CARP_NOT); # package scope
502 @My::Package::CARP_NOT = ... ; # explicit package variable
505 sub xyz { ... @CARP_NOT = ... } # w/o declarations above
506 my @CARP_NOT; # even at top-level
510 package My::Carping::Package;
513 sub bar { .... or _error('Wrong input') }
515 # temporary control of where'ness, __PACKAGE__ is implicit
516 local @CARP_NOT = qw(My::Friendly::Caller);
520 This would make C<Carp> report the error as coming from a caller not
521 in C<My::Carping::Package>, nor from C<My::Friendly::Caller>.
523 Also read the L</DESCRIPTION> section above, about how C<Carp> decides
524 where the error is reported from.
526 Use C<@CARP_NOT>, instead of C<$Carp::CarpLevel>.
528 Overrides C<Carp>'s use of C<@ISA>.
530 =head2 %Carp::Internal
532 This says what packages are internal to Perl. C<Carp> will never
533 report an error as being from a line in a package that is internal to
536 $Carp::Internal{ (__PACKAGE__) }++;
538 sub foo { ... or confess("whatever") };
540 would give a full stack backtrace starting from the first caller
541 outside of __PACKAGE__. (Unless that package was also internal to
544 =head2 %Carp::CarpInternal
546 This says which packages are internal to Perl's warning system. For
547 generating a full stack backtrace this is the same as being internal
548 to Perl, the stack backtrace will not start inside packages that are
549 listed in C<%Carp::CarpInternal>. But it is slightly different for
550 the summary message generated by C<carp> or C<croak>. There errors
551 will not be reported on any lines that are calling packages in
552 C<%Carp::CarpInternal>.
554 For example C<Carp> itself is listed in C<%Carp::CarpInternal>.
555 Therefore the full stack backtrace from C<confess> will not start
556 inside of C<Carp>, and the short message from calling C<croak> is
557 not placed on the line where C<croak> was called.
559 =head2 $Carp::CarpLevel
561 This variable determines how many additional call frames are to be
562 skipped that would not otherwise be when reporting where an error
563 occurred on a call to one of C<Carp>'s functions. It is fairly easy
564 to count these call frames on calls that generate a full stack
565 backtrace. However it is much harder to do this accounting for calls
566 that generate a short message. Usually people skip too many call
567 frames. If they are lucky they skip enough that C<Carp> goes all of
568 the way through the call stack, realizes that something is wrong, and
569 then generates a full stack backtrace. If they are unlucky then the
570 error is reported from somewhere misleading very high in the call
573 Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use
574 C<@CARP_NOT>, C<%Carp::Internal> and C<%Carp::CarpInternal>.
580 The Carp routines don't handle exception objects currently.
581 If called with a first argument that is a reference, they simply
582 call die() or warn(), as appropriate.