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 $call_pack = caller();
47 if ($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 = 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 qw(pack file line sub has_args wantarray evaltext is_require)
75 unless (defined $call_info{pack}) {
79 my $sub_name = Carp::get_subname(\%call_info);
80 if ($call_info{has_args}) {
81 my @args = map {Carp::format_arg($_)} @DB::args;
82 if ($MaxArgNums and @args > $MaxArgNums) { # More than we want to show?
86 # Push the args onto the subroutine
87 $sub_name .= '(' . join (', ', @args) . ')';
89 $call_info{sub_name} = $sub_name;
90 return wantarray() ? %call_info : \%call_info;
93 # Transform an argument to a function into a string.
97 $arg = defined($overload::VERSION) ? overload::StrVal($arg) : "$arg";
101 $arg = str_len_trim($arg, $MaxArgLen);
104 $arg = "'$arg'" unless $arg =~ /^-?[\d.]+\z/;
109 # The following handling of "control chars" is direct from
110 # the original code - it is broken on Unicode though.
113 or $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;
117 # Takes an inheritance cache and a package and returns
118 # an anon hash of known inheritances and anon array of
119 # inheritances which consequences have not been figured
124 $cache->{$pkg} ||= [{$pkg => $pkg}, [trusts_directly($pkg)]];
125 return @{$cache->{$pkg}};
128 # Takes the info from caller() and figures out the name of
129 # the sub/require/eval
132 if (defined($info->{evaltext})) {
133 my $eval = $info->{evaltext};
134 if ($info->{is_require}) {
135 return "require $eval";
138 $eval =~ s/([\\\'])/\\$1/g;
139 return "eval '" . str_len_trim($eval, $MaxEvalLen) . "'";
143 return ($info->{sub} eq '(eval)') ? 'eval {...}' : $info->{sub};
146 # Figures out what call (from the point of view of the caller)
147 # the long error backtrace should start at.
150 my $lvl = $CarpLevel;
152 my $pkg = caller(++$i);
153 unless(defined($pkg)) {
154 # This *shouldn't* happen.
157 $i = long_error_loc();
161 # OK, now I am irritated.
165 redo if $CarpInternal{$pkg};
166 redo unless 0 > --$lvl;
167 redo if $Internal{$pkg};
174 return @_ if ref($_[0]); # don't break references as exceptions
175 my $i = long_error_loc();
176 return ret_backtrace($i, @_);
179 # Returns a full stack backtrace starting from where it is
182 my ($i, @error) = @_;
184 my $err = join '', @error;
188 if (defined &threads::tid) {
189 my $tid = threads->tid;
190 $tid_msg = " thread $tid" if $tid;
193 my %i = caller_info($i);
194 $mess = "$err at $i{file} line $i{line}$tid_msg\n";
196 while (my %i = caller_info(++$i)) {
197 $mess .= "\t$i{sub_name} called at $i{file} line $i{line}$tid_msg\n";
204 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 return "$err at $i{file} line $i{line}$tid_msg\n";
219 sub short_error_loc {
220 # You have to create your (hash)ref out here, rather than defaulting it
221 # inside trusts *on a lexical*, as you want it to persist across calls.
222 # (You can default it on $_[2], but that gets messy)
225 my $lvl = $CarpLevel;
227 my $called = caller($i++);
228 my $caller = caller($i);
230 return 0 unless defined($caller); # What happened?
231 redo if $Internal{$caller};
232 redo if $CarpInternal{$caller};
233 redo if $CarpInternal{$called};
234 redo if trusts($called, $caller, $cache);
235 redo if trusts($caller, $called, $cache);
236 redo unless 0 > --$lvl;
242 sub shortmess_heavy {
243 return longmess_heavy(@_) if $Verbose;
244 return @_ if ref($_[0]); # don't break references as exceptions
245 my $i = short_error_loc();
254 # If a string is too long, trims it with ...
257 my $max = shift || 0;
258 if (2 < $max and $max < length($str)) {
259 substr($str, $max - 3) = '...';
264 # Takes two packages and an optional cache. Says whether the
265 # first inherits from the second.
267 # Recursive versions of this have to work to avoid certain
268 # possible endless loops, and when following long chains of
269 # inheritance are less efficient.
274 my ($known, $partial) = get_status($cache, $child);
275 # Figure out consequences until we have an answer
276 while (@$partial and not exists $known->{$parent}) {
277 my $anc = shift @$partial;
278 next if exists $known->{$anc};
280 my ($anc_knows, $anc_partial) = get_status($cache, $anc);
281 my @found = keys %$anc_knows;
282 @$known{@found} = ();
283 push @$partial, @$anc_partial;
285 return exists $known->{$parent};
288 # Takes a package and gives a list of those trusted directly
289 sub trusts_directly {
293 return @{"$class\::CARP_NOT"}
294 ? @{"$class\::CARP_NOT"}
304 carp - warn of errors (from perspective of caller)
306 cluck - warn of errors with stack backtrace
307 (not exported by default)
309 croak - die of errors (from perspective of caller)
311 confess - die of errors with stack backtrace
316 croak "We're outta here!";
319 cluck "This is how we got here!";
323 The Carp routines are useful in your own modules because
324 they act like die() or warn(), but with a message which is more
325 likely to be useful to a user of your module. In the case of
326 cluck, confess, and longmess that context is a summary of every
327 call in the call-stack. For a shorter message you can use C<carp>
328 or C<croak> which report the error as being from where your module
329 was called. There is no guarantee that that is where the error
330 was, but it is a good educated guess.
332 You can also alter the way the output and logic of C<Carp> works, by
333 changing some global variables in the C<Carp> namespace. See the
334 section on C<GLOBAL VARIABLES> below.
336 Here is a more complete description of how C<carp> and C<croak> work.
337 What they do is search the call-stack for a function call stack where
338 they have not been told that there shouldn't be an error. If every
339 call is marked safe, they give up and give a full stack backtrace
340 instead. In other words they presume that the first likely looking
341 potential suspect is guilty. Their rules for telling whether
342 a call shouldn't generate errors work as follows:
348 Any call from a package to itself is safe.
352 Packages claim that there won't be errors on calls to or from
353 packages explicitly marked as safe by inclusion in C<@CARP_NOT>, or
354 (if that array is empty) C<@ISA>. The ability to override what
355 @ISA says is new in 5.8.
359 The trust in item 2 is transitive. If A trusts B, and B
360 trusts C, then A trusts C. So if you do not override C<@ISA>
361 with C<@CARP_NOT>, then this trust relationship is identical to,
366 Any call from an internal Perl module is safe. (Nothing keeps
367 user modules from marking themselves as internal to Perl, but
368 this practice is discouraged.)
372 Any call to Perl's warning system (eg Carp itself) is safe.
373 (This rule is what keeps it from reporting the error at the
374 point where you call C<carp> or C<croak>.)
378 C<$Carp::CarpLevel> can be set to skip a fixed number of additional
379 call levels. Using this is not recommended because it is very
380 difficult to get it to behave correctly.
384 =head2 Forcing a Stack Trace
386 As a debugging aid, you can force Carp to treat a croak as a confess
387 and a carp as a cluck across I<all> modules. In other words, force a
388 detailed stack trace to be given. This can be very helpful when trying
389 to understand why, or from where, a warning or error is being generated.
391 This feature is enabled by 'importing' the non-existent symbol
392 'verbose'. You would typically enable it by saying
394 perl -MCarp=verbose script.pl
396 or by including the string C<-MCarp=verbose> in the PERL5OPT
397 environment variable.
399 Alternately, you can set the global variable C<$Carp::Verbose> to true.
400 See the C<GLOBAL VARIABLES> section below.
402 =head1 GLOBAL VARIABLES
404 =head2 $Carp::MaxEvalLen
406 This variable determines how many characters of a string-eval are to
407 be shown in the output. Use a value of C<0> to show all text.
411 =head2 $Carp::MaxArgLen
413 This variable determines how many characters of each argument to a
414 function to print. Use a value of C<0> to show the full length of the
419 =head2 $Carp::MaxArgNums
421 This variable determines how many arguments to each function to show.
422 Use a value of C<0> to show all arguments to a function call.
426 =head2 $Carp::Verbose
428 This variable makes C<carp> and C<cluck> generate stack backtraces
429 just like C<cluck> and C<confess>. This is how C<use Carp 'verbose'>
430 is implemented internally.
436 This variable, I<in your package>, says which packages are I<not> to be
437 considered as the location of an error. The C<carp()> and C<cluck()>
438 functions will skip over callers when reporting where an error occurred.
440 NB: This variable must be in the package's symbol table, thus:
443 our @CARP_NOT; # file scope
444 use vars qw(@CARP_NOT); # package scope
445 @My::Package::CARP_NOT = ... ; # explicit package variable
448 sub xyz { ... @CARP_NOT = ... } # w/o declarations above
449 my @CARP_NOT; # even at top-level
453 package My::Carping::Package;
456 sub bar { .... or _error('Wrong input') }
458 # temporary control of where'ness, __PACKAGE__ is implicit
459 local @CARP_NOT = qw(My::Friendly::Caller);
463 This would make C<Carp> report the error as coming from a caller not
464 in C<My::Carping::Package>, nor from C<My::Friendly::Caller>.
466 Also read the L</"Description"> section above, about how C<Carp> decides
467 where the error is reported from.
469 Use C<@CARP_NOT>, instead of C<$Carp::CarpLevel>.
471 Overrides C<Carp>'s use of C<@ISA>.
473 =head2 %Carp::Internal
475 This says what packages are internal to Perl. C<Carp> will never
476 report an error as being from a line in a package that is internal to
479 $Carp::Internal{ (__PACKAGE__) }++;
481 sub foo { ... or confess("whatever") };
483 would give a full stack backtrace starting from the first caller
484 outside of __PACKAGE__. (Unless that package was also internal to
487 =head2 %Carp::CarpInternal
489 This says which packages are internal to Perl's warning system. For
490 generating a full stack backtrace this is the same as being internal
491 to Perl, the stack backtrace will not start inside packages that are
492 listed in C<%Carp::CarpInternal>. But it is slightly different for
493 the summary message generated by C<carp> or C<croak>. There errors
494 will not be reported on any lines that are calling packages in
495 C<%Carp::CarpInternal>.
497 For example C<Carp> itself is listed in C<%Carp::CarpInternal>.
498 Therefore the full stack backtrace from C<confess> will not start
499 inside of C<Carp>, and the short message from calling C<croak> is
500 not placed on the line where C<croak> was called.
502 =head2 $Carp::CarpLevel
504 This variable determines how many additional call frames are to be
505 skipped that would not otherwise be when reporting where an error
506 occurred on a call to one of C<Carp>'s functions. It is fairly easy
507 to count these call frames on calls that generate a full stack
508 backtrace. However it is much harder to do this accounting for calls
509 that generate a short message. Usually people skip too many call
510 frames. If they are lucky they skip enough that C<Carp> goes all of
511 the way through the call stack, realizes that something is wrong, and
512 then generates a full stack backtrace. If they are unlucky then the
513 error is reported from somewhere misleading very high in the call
516 Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use
517 C<@CARP_NOT>, C<%Carp::Internal> and C<%Carp::CarpInternal>.
523 The Carp routines don't handle exception objects currently.
524 If called with a first argument that is a reference, they simply
525 call die() or warn(), as appropriate.