8 our $MaxArgLen = 64; # How much of each argument to print. 0 = all.
9 our $MaxArgNums = 8; # How many arguments to print. 0 = all.
12 our @ISA = ('Exporter');
13 our @EXPORT = qw(confess croak carp);
14 our @EXPORT_OK = qw(cluck verbose longmess shortmess);
15 our @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
17 # The members of %Internal are packages that are internal to perl.
18 # Carp will not report errors from within these packages if it
19 # can. The members of %CarpInternal are internal to Perl's warning
20 # system. Carp will not report errors from within these packages
21 # either, and will not report calls *to* these packages for carp and
22 # croak. They replace $CarpLevel, which is deprecated. The
23 # $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
24 # text and function arguments should be formatted when printed.
26 # disable these by default, so they can live w/o require Carp
27 $CarpInternal{Carp}++;
28 $CarpInternal{warnings}++;
29 $Internal{Exporter}++;
30 $Internal{'Exporter::Heavy'}++;
32 # if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
33 # then the following method will be called by the Exporter which knows
34 # to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word
37 sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ }
40 # Icky backwards compatibility wrapper. :-(
42 # The story is that the original implementation hard-coded the
43 # number of call levels to go back, so calls to longmess were off
44 # by one. Other code began calling longmess and expecting this
45 # behaviour, so the replacement has to emulate that behaviour.
46 my $call_pack = defined &{"CORE::GLOBAL::caller"} ? &{"CORE::GLOBAL::caller"}() : caller();
47 if ($Internal{$call_pack} or $CarpInternal{$call_pack}) {
48 return longmess_heavy(@_);
51 local $CarpLevel = $CarpLevel + 1;
52 return longmess_heavy(@_);
57 # Icky backwards compatibility wrapper. :-(
58 local @CARP_NOT = defined &{"CORE::GLOBAL::caller"} ? &{"CORE::GLOBAL::caller"}() : caller();
62 sub croak { die shortmess @_ }
63 sub confess { die longmess @_ }
64 sub carp { warn shortmess @_ }
65 sub cluck { warn longmess @_ }
68 my $i = shift(@_) + 1;
72 @args = \$i; # A sentinal, which no-one else has the address of
74 qw(pack file line sub has_args wantarray evaltext is_require)
75 } = defined &{"CORE::GLOBAL::caller"} ? &{"CORE::GLOBAL::caller"}($i) : caller($i);
78 unless (defined $call_info{pack}) {
82 my $sub_name = Carp::get_subname(\%call_info);
83 if ($call_info{has_args}) {
85 if (@DB::args == 1 && ref $DB::args[0] eq ref \$i && $DB::args[0] == \$i) {
86 @DB::args = (); # Don't let anyone see the address of $i
89 my $func = defined &{"CORE::GLOBAL::caller"} ? \&{"CORE::GLOBAL::caller"} : return '';
90 my $gv = B::svref_2object($func)->GV;
91 my $package = $gv->STASH->NAME;
92 my $subname = $gv->NAME;
93 return unless defined $package && defined $subname;
94 # returning CORE::GLOBAL::caller isn't useful for tracing the cause:
95 return if $package eq 'CORE::GLOBAL' && $subname eq 'caller';
96 " in &${package}::$subname";
98 @args = "** Incomplete caller override detected$where; \@DB::args were not set **";
100 @args = map {Carp::format_arg($_)} @DB::args;
102 if ($MaxArgNums and @args > $MaxArgNums) { # More than we want to show?
103 $#args = $MaxArgNums;
106 # Push the args onto the subroutine
107 $sub_name .= '(' . join (', ', @args) . ')';
109 $call_info{sub_name} = $sub_name;
110 return wantarray() ? %call_info : \%call_info;
113 # Transform an argument to a function into a string.
117 $arg = defined($overload::VERSION) ? overload::StrVal($arg) : "$arg";
121 $arg = str_len_trim($arg, $MaxArgLen);
124 $arg = "'$arg'" unless $arg =~ /^-?[\d.]+\z/;
129 # The following handling of "control chars" is direct from
130 # the original code - it is broken on Unicode though.
133 or $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;
137 # Takes an inheritance cache and a package and returns
138 # an anon hash of known inheritances and anon array of
139 # inheritances which consequences have not been figured
144 $cache->{$pkg} ||= [{$pkg => $pkg}, [trusts_directly($pkg)]];
145 return @{$cache->{$pkg}};
148 # Takes the info from caller() and figures out the name of
149 # the sub/require/eval
152 if (defined($info->{evaltext})) {
153 my $eval = $info->{evaltext};
154 if ($info->{is_require}) {
155 return "require $eval";
158 $eval =~ s/([\\\'])/\\$1/g;
159 return "eval '" . str_len_trim($eval, $MaxEvalLen) . "'";
163 return ($info->{sub} eq '(eval)') ? 'eval {...}' : $info->{sub};
166 # Figures out what call (from the point of view of the caller)
167 # the long error backtrace should start at.
170 my $lvl = $CarpLevel;
173 my $pkg = defined &{"CORE::GLOBAL::caller"} ? &{"CORE::GLOBAL::caller"}($i) : caller($i);
174 unless(defined($pkg)) {
175 # This *shouldn't* happen.
178 $i = long_error_loc();
182 # OK, now I am irritated.
186 redo if $CarpInternal{$pkg};
187 redo unless 0 > --$lvl;
188 redo if $Internal{$pkg};
195 return @_ if ref($_[0]); # don't break references as exceptions
196 my $i = long_error_loc();
197 return ret_backtrace($i, @_);
200 # Returns a full stack backtrace starting from where it is
203 my ($i, @error) = @_;
205 my $err = join '', @error;
209 if (defined &threads::tid) {
210 my $tid = threads->tid;
211 $tid_msg = " thread $tid" if $tid;
214 my %i = caller_info($i);
215 $mess = "$err at $i{file} line $i{line}$tid_msg\n";
217 while (my %i = caller_info(++$i)) {
218 $mess .= "\t$i{sub_name} called at $i{file} line $i{line}$tid_msg\n";
225 my ($i, @error) = @_;
226 my $err = join '', @error;
230 if (defined &threads::tid) {
231 my $tid = threads->tid;
232 $tid_msg = " thread $tid" if $tid;
235 my %i = caller_info($i);
236 return "$err at $i{file} line $i{line}$tid_msg\n";
240 sub short_error_loc {
241 # You have to create your (hash)ref out here, rather than defaulting it
242 # inside trusts *on a lexical*, as you want it to persist across calls.
243 # (You can default it on $_[2], but that gets messy)
246 my $lvl = $CarpLevel;
249 my $called = defined &{"CORE::GLOBAL::caller"} ? &{"CORE::GLOBAL::caller"}($i) : caller($i);
251 my $caller = defined &{"CORE::GLOBAL::caller"} ? &{"CORE::GLOBAL::caller"}($i) : caller($i);
253 return 0 unless defined($caller); # What happened?
254 redo if $Internal{$caller};
255 redo if $CarpInternal{$caller};
256 redo if $CarpInternal{$called};
257 redo if trusts($called, $caller, $cache);
258 redo if trusts($caller, $called, $cache);
259 redo unless 0 > --$lvl;
265 sub shortmess_heavy {
266 return longmess_heavy(@_) if $Verbose;
267 return @_ if ref($_[0]); # don't break references as exceptions
268 my $i = short_error_loc();
277 # If a string is too long, trims it with ...
280 my $max = shift || 0;
281 if (2 < $max and $max < length($str)) {
282 substr($str, $max - 3) = '...';
287 # Takes two packages and an optional cache. Says whether the
288 # first inherits from the second.
290 # Recursive versions of this have to work to avoid certain
291 # possible endless loops, and when following long chains of
292 # inheritance are less efficient.
297 my ($known, $partial) = get_status($cache, $child);
298 # Figure out consequences until we have an answer
299 while (@$partial and not exists $known->{$parent}) {
300 my $anc = shift @$partial;
301 next if exists $known->{$anc};
303 my ($anc_knows, $anc_partial) = get_status($cache, $anc);
304 my @found = keys %$anc_knows;
305 @$known{@found} = ();
306 push @$partial, @$anc_partial;
308 return exists $known->{$parent};
311 # Takes a package and gives a list of those trusted directly
312 sub trusts_directly {
316 return @{"$class\::CARP_NOT"}
317 ? @{"$class\::CARP_NOT"}
327 carp - warn of errors (from perspective of caller)
329 cluck - warn of errors with stack backtrace
330 (not exported by default)
332 croak - die of errors (from perspective of caller)
334 confess - die of errors with stack backtrace
339 croak "We're outta here!";
342 cluck "This is how we got here!";
346 The Carp routines are useful in your own modules because
347 they act like die() or warn(), but with a message which is more
348 likely to be useful to a user of your module. In the case of
349 cluck, confess, and longmess that context is a summary of every
350 call in the call-stack. For a shorter message you can use C<carp>
351 or C<croak> which report the error as being from where your module
352 was called. There is no guarantee that that is where the error
353 was, but it is a good educated guess.
355 You can also alter the way the output and logic of C<Carp> works, by
356 changing some global variables in the C<Carp> namespace. See the
357 section on C<GLOBAL VARIABLES> below.
359 Here is a more complete description of how C<carp> and C<croak> work.
360 What they do is search the call-stack for a function call stack where
361 they have not been told that there shouldn't be an error. If every
362 call is marked safe, they give up and give a full stack backtrace
363 instead. In other words they presume that the first likely looking
364 potential suspect is guilty. Their rules for telling whether
365 a call shouldn't generate errors work as follows:
371 Any call from a package to itself is safe.
375 Packages claim that there won't be errors on calls to or from
376 packages explicitly marked as safe by inclusion in C<@CARP_NOT>, or
377 (if that array is empty) C<@ISA>. The ability to override what
378 @ISA says is new in 5.8.
382 The trust in item 2 is transitive. If A trusts B, and B
383 trusts C, then A trusts C. So if you do not override C<@ISA>
384 with C<@CARP_NOT>, then this trust relationship is identical to,
389 Any call from an internal Perl module is safe. (Nothing keeps
390 user modules from marking themselves as internal to Perl, but
391 this practice is discouraged.)
395 Any call to Perl's warning system (eg Carp itself) is safe.
396 (This rule is what keeps it from reporting the error at the
397 point where you call C<carp> or C<croak>.)
401 C<$Carp::CarpLevel> can be set to skip a fixed number of additional
402 call levels. Using this is not recommended because it is very
403 difficult to get it to behave correctly.
407 =head2 Forcing a Stack Trace
409 As a debugging aid, you can force Carp to treat a croak as a confess
410 and a carp as a cluck across I<all> modules. In other words, force a
411 detailed stack trace to be given. This can be very helpful when trying
412 to understand why, or from where, a warning or error is being generated.
414 This feature is enabled by 'importing' the non-existent symbol
415 'verbose'. You would typically enable it by saying
417 perl -MCarp=verbose script.pl
419 or by including the string C<-MCarp=verbose> in the PERL5OPT
420 environment variable.
422 Alternately, you can set the global variable C<$Carp::Verbose> to true.
423 See the C<GLOBAL VARIABLES> section below.
425 =head1 GLOBAL VARIABLES
427 =head2 $Carp::MaxEvalLen
429 This variable determines how many characters of a string-eval are to
430 be shown in the output. Use a value of C<0> to show all text.
434 =head2 $Carp::MaxArgLen
436 This variable determines how many characters of each argument to a
437 function to print. Use a value of C<0> to show the full length of the
442 =head2 $Carp::MaxArgNums
444 This variable determines how many arguments to each function to show.
445 Use a value of C<0> to show all arguments to a function call.
449 =head2 $Carp::Verbose
451 This variable makes C<carp> and C<croak> generate stack backtraces
452 just like C<cluck> and C<confess>. This is how C<use Carp 'verbose'>
453 is implemented internally.
459 This variable, I<in your package>, says which packages are I<not> to be
460 considered as the location of an error. The C<carp()> and C<cluck()>
461 functions will skip over callers when reporting where an error occurred.
463 NB: This variable must be in the package's symbol table, thus:
466 our @CARP_NOT; # file scope
467 use vars qw(@CARP_NOT); # package scope
468 @My::Package::CARP_NOT = ... ; # explicit package variable
471 sub xyz { ... @CARP_NOT = ... } # w/o declarations above
472 my @CARP_NOT; # even at top-level
476 package My::Carping::Package;
479 sub bar { .... or _error('Wrong input') }
481 # temporary control of where'ness, __PACKAGE__ is implicit
482 local @CARP_NOT = qw(My::Friendly::Caller);
486 This would make C<Carp> report the error as coming from a caller not
487 in C<My::Carping::Package>, nor from C<My::Friendly::Caller>.
489 Also read the L</DESCRIPTION> section above, about how C<Carp> decides
490 where the error is reported from.
492 Use C<@CARP_NOT>, instead of C<$Carp::CarpLevel>.
494 Overrides C<Carp>'s use of C<@ISA>.
496 =head2 %Carp::Internal
498 This says what packages are internal to Perl. C<Carp> will never
499 report an error as being from a line in a package that is internal to
502 $Carp::Internal{ (__PACKAGE__) }++;
504 sub foo { ... or confess("whatever") };
506 would give a full stack backtrace starting from the first caller
507 outside of __PACKAGE__. (Unless that package was also internal to
510 =head2 %Carp::CarpInternal
512 This says which packages are internal to Perl's warning system. For
513 generating a full stack backtrace this is the same as being internal
514 to Perl, the stack backtrace will not start inside packages that are
515 listed in C<%Carp::CarpInternal>. But it is slightly different for
516 the summary message generated by C<carp> or C<croak>. There errors
517 will not be reported on any lines that are calling packages in
518 C<%Carp::CarpInternal>.
520 For example C<Carp> itself is listed in C<%Carp::CarpInternal>.
521 Therefore the full stack backtrace from C<confess> will not start
522 inside of C<Carp>, and the short message from calling C<croak> is
523 not placed on the line where C<croak> was called.
525 =head2 $Carp::CarpLevel
527 This variable determines how many additional call frames are to be
528 skipped that would not otherwise be when reporting where an error
529 occurred on a call to one of C<Carp>'s functions. It is fairly easy
530 to count these call frames on calls that generate a full stack
531 backtrace. However it is much harder to do this accounting for calls
532 that generate a short message. Usually people skip too many call
533 frames. If they are lucky they skip enough that C<Carp> goes all of
534 the way through the call stack, realizes that something is wrong, and
535 then generates a full stack backtrace. If they are unlucky then the
536 error is reported from somewhere misleading very high in the call
539 Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use
540 C<@CARP_NOT>, C<%Carp::Internal> and C<%Carp::CarpInternal>.
546 The Carp routines don't handle exception objects currently.
547 If called with a first argument that is a reference, they simply
548 call die() or warn(), as appropriate.