summaryrefslogtreecommitdiff
path: root/systems/texlive/tlnet/tlpkg/tlperl/lib/Carp.pm
blob: 109b7fec7703f2f1211bcd67c24f2fc57ae0de81 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
package Carp;

{ use 5.006; }
use strict;
use warnings;
BEGIN {
    # Very old versions of warnings.pm load Carp.  This can go wrong due
    # to the circular dependency.  If warnings is invoked before Carp,
    # then warnings starts by loading Carp, then Carp (above) tries to
    # invoke warnings, and gets nothing because warnings is in the process
    # of loading and hasn't defined its import method yet.  If we were
    # only turning on warnings ("use warnings" above) this wouldn't be too
    # bad, because Carp would just gets the state of the -w switch and so
    # might not get some warnings that it wanted.  The real problem is
    # that we then want to turn off Unicode warnings, but "no warnings
    # 'utf8'" won't be effective if we're in this circular-dependency
    # situation.  So, if warnings.pm is an affected version, we turn
    # off all warnings ourselves by directly setting ${^WARNING_BITS}.
    # On unaffected versions, we turn off just Unicode warnings, via
    # the proper API.
    if(!defined($warnings::VERSION) || eval($warnings::VERSION) < 1.06) {
	${^WARNING_BITS} = "";
    } else {
	"warnings"->unimport("utf8");
    }
}

sub _fetch_sub { # fetch sub without autovivifying
    my($pack, $sub) = @_;
    $pack .= '::';
    # only works with top-level packages
    return unless exists($::{$pack});
    for ($::{$pack}) {
	return unless ref \$_ eq 'GLOB' && *$_{HASH} && exists $$_{$sub};
	for ($$_{$sub}) {
	    return ref \$_ eq 'GLOB' ? *$_{CODE} : undef
	}
    }
}

# UTF8_REGEXP_PROBLEM is a compile-time constant indicating whether Carp
# must avoid applying a regular expression to an upgraded (is_utf8)
# string.  There are multiple problems, on different Perl versions,
# that require this to be avoided.  All versions prior to 5.13.8 will
# load utf8_heavy.pl for the swash system, even if the regexp doesn't
# use character classes.  Perl 5.6 and Perls [5.11.2, 5.13.11) exhibit
# specific problems when Carp is being invoked in the aftermath of a
# syntax error.
BEGIN {
    if("$]" < 5.013011) {
	*UTF8_REGEXP_PROBLEM = sub () { 1 };
    } else {
	*UTF8_REGEXP_PROBLEM = sub () { 0 };
    }
}

# is_utf8() is essentially the utf8::is_utf8() function, which indicates
# whether a string is represented in the upgraded form (using UTF-8
# internally).  As utf8::is_utf8() is only available from Perl 5.8
# onwards, extra effort is required here to make it work on Perl 5.6.
BEGIN {
    if(defined(my $sub = _fetch_sub utf8 => 'is_utf8')) {
	*is_utf8 = $sub;
    } else {
	# black magic for perl 5.6
	*is_utf8 = sub { unpack("C", "\xaa".$_[0]) != 170 };
    }
}

# The downgrade() function defined here is to be used for attempts to
# downgrade where it is acceptable to fail.  It must be called with a
# second argument that is a true value.
BEGIN {
    if(defined(my $sub = _fetch_sub utf8 => 'downgrade')) {
	*downgrade = \&{"utf8::downgrade"};
    } else {
	*downgrade = sub {
	    my $r = "";
	    my $l = length($_[0]);
	    for(my $i = 0; $i != $l; $i++) {
		my $o = ord(substr($_[0], $i, 1));
		return if $o > 255;
		$r .= chr($o);
	    }
	    $_[0] = $r;
	};
    }
}

# is_safe_printable_codepoint() indicates whether a character, specified
# by integer codepoint, is OK to output literally in a trace.  Generally
# this is if it is a printable character in the ancestral character set
# (ASCII or EBCDIC).  This is used on some Perls in situations where a
# regexp can't be used.
BEGIN {
    *is_safe_printable_codepoint =
	"$]" >= 5.007_003 ?
	    eval(q(sub ($) {
		my $u = utf8::native_to_unicode($_[0]);
		$u >= 0x20 && $u <= 0x7e;
	    }))
	: ord("A") == 65 ?
	    sub ($) { $_[0] >= 0x20 && $_[0] <= 0x7e }
	:
	    sub ($) {
		# Early EBCDIC
		# 3 EBCDIC code pages supported then;  all controls but one
		# are the code points below SPACE.  The other one is 0x5F on
		# POSIX-BC; FF on the other two.
		# FIXME: there are plenty of unprintable codepoints other
		# than those that this code and the comment above identifies
		# as "controls".
		$_[0] >= ord(" ") && $_[0] <= 0xff &&
		    $_[0] != (ord ("^") == 106 ? 0x5f : 0xff);
	    }
	;
}

sub _univ_mod_loaded {
    return 0 unless exists($::{"UNIVERSAL::"});
    for ($::{"UNIVERSAL::"}) {
	return 0 unless ref \$_ eq "GLOB" && *$_{HASH} && exists $$_{"$_[0]::"};
	for ($$_{"$_[0]::"}) {
	    return 0 unless ref \$_ eq "GLOB" && *$_{HASH} && exists $$_{"VERSION"};
	    for ($$_{"VERSION"}) {
		return 0 unless ref \$_ eq "GLOB";
		return ${*$_{SCALAR}};
	    }
	}
    }
}

# _maybe_isa() is usually the UNIVERSAL::isa function.  We have to avoid
# the latter if the UNIVERSAL::isa module has been loaded, to avoid infi-
# nite recursion; in that case _maybe_isa simply returns true.
my $isa;
BEGIN {
    if (_univ_mod_loaded('isa')) {
        *_maybe_isa = sub { 1 }
    }
    else {
        # Since we have already done the check, record $isa for use below
        # when defining _StrVal.
        *_maybe_isa = $isa = _fetch_sub(UNIVERSAL => "isa");
    }
}


# We need an overload::StrVal or equivalent function, but we must avoid
# loading any modules on demand, as Carp is used from __DIE__ handlers and
# may be invoked after a syntax error.
# We can copy recent implementations of overload::StrVal and use
# overloading.pm, which is the fastest implementation, so long as
# overloading is available.  If it is not available, we use our own pure-
# Perl StrVal.  We never actually use overload::StrVal, for various rea-
# sons described below.
# overload versions are as follows:
#     undef-1.00 (up to perl 5.8.0)   uses bless (avoid!)
#     1.01-1.17  (perl 5.8.1 to 5.14) uses Scalar::Util
#     1.18+      (perl 5.16+)         uses overloading
# The ancient 'bless' implementation (that inspires our pure-Perl version)
# blesses unblessed references and must be avoided.  Those using
# Scalar::Util use refaddr, possibly the pure-Perl implementation, which
# has the same blessing bug, and must be avoided.  Also, Scalar::Util is
# loaded on demand.  Since we avoid the Scalar::Util implementations, we
# end up having to implement our own overloading.pm-based version for perl
# 5.10.1 to 5.14.  Since it also works just as well in more recent ver-
# sions, we use it there, too.
BEGIN {
    if (eval { require "overloading.pm" }) {
        *_StrVal = eval 'sub { no overloading; "$_[0]" }'
    }
    else {
        # Work around the UNIVERSAL::can/isa modules to avoid recursion.

        # _mycan is either UNIVERSAL::can, or, in the presence of an
        # override, overload::mycan.
        *_mycan = _univ_mod_loaded('can')
            ? do { require "overload.pm"; _fetch_sub overload => 'mycan' }
            : \&UNIVERSAL::can;

        # _blessed is either UNIVERAL::isa(...), or, in the presence of an
        # override, a hideous, but fairly reliable, workaround.
        *_blessed = $isa
            ? sub { &$isa($_[0], "UNIVERSAL") }
            : sub {
                my $probe = "UNIVERSAL::Carp_probe_" . rand;
                no strict 'refs';
                local *$probe = sub { "unlikely string" };
                local $@;
                local $SIG{__DIE__} = sub{};
                (eval { $_[0]->$probe } || '') eq 'unlikely string'
              };

        *_StrVal = sub {
            my $pack = ref $_[0];
            # Perl's overload mechanism uses the presence of a special
            # "method" named "((" or "()" to signal it is in effect.
            # This test seeks to see if it has been set up.  "((" post-
            # dates overloading.pm, so we can skip it.
            return "$_[0]" unless _mycan($pack, "()");
            # Even at this point, the invocant may not be blessed, so
            # check for that.
            return "$_[0]" if not _blessed($_[0]);
            bless $_[0], "Carp";
            my $str = "$_[0]";
            bless $_[0], $pack;
            $pack . substr $str, index $str, "=";
        }
    }
}


our $VERSION = '1.50';
$VERSION =~ tr/_//d;

our $MaxEvalLen = 0;
our $Verbose    = 0;
our $CarpLevel  = 0;
our $MaxArgLen  = 64;    # How much of each argument to print. 0 = all.
our $MaxArgNums = 8;     # How many arguments to print. 0 = all.
our $RefArgFormatter = undef; # allow caller to format reference arguments

require Exporter;
our @ISA       = ('Exporter');
our @EXPORT    = qw(confess croak carp);
our @EXPORT_OK = qw(cluck verbose longmess shortmess);
our @EXPORT_FAIL = qw(verbose);    # hook to enable verbose mode

# The members of %Internal are packages that are internal to perl.
# Carp will not report errors from within these packages if it
# can.  The members of %CarpInternal are internal to Perl's warning
# system.  Carp will not report errors from within these packages
# either, and will not report calls *to* these packages for carp and
# croak.  They replace $CarpLevel, which is deprecated.    The
# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
# text and function arguments should be formatted when printed.

our %CarpInternal;
our %Internal;

# disable these by default, so they can live w/o require Carp
$CarpInternal{Carp}++;
$CarpInternal{warnings}++;
$Internal{Exporter}++;
$Internal{'Exporter::Heavy'}++;

# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
# then the following method will be called by the Exporter which knows
# to do this thanks to @EXPORT_FAIL, above.  $_[1] will contain the word
# 'verbose'.

sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ }

sub _cgc {
    no strict 'refs';
    return \&{"CORE::GLOBAL::caller"} if defined &{"CORE::GLOBAL::caller"};
    return;
}

sub longmess {
    local($!, $^E);
    # Icky backwards compatibility wrapper. :-(
    #
    # The story is that the original implementation hard-coded the
    # number of call levels to go back, so calls to longmess were off
    # by one.  Other code began calling longmess and expecting this
    # behaviour, so the replacement has to emulate that behaviour.
    my $cgc = _cgc();
    my $call_pack = $cgc ? $cgc->() : caller();
    if ( $Internal{$call_pack} or $CarpInternal{$call_pack} ) {
        return longmess_heavy(@_);
    }
    else {
        local $CarpLevel = $CarpLevel + 1;
        return longmess_heavy(@_);
    }
}

our @CARP_NOT;

sub shortmess {
    local($!, $^E);
    my $cgc = _cgc();

    # Icky backwards compatibility wrapper. :-(
    local @CARP_NOT = $cgc ? $cgc->() : caller();
    shortmess_heavy(@_);
}

sub croak   { die shortmess @_ }
sub confess { die longmess @_ }
sub carp    { warn shortmess @_ }
sub cluck   { warn longmess @_ }

BEGIN {
    if("$]" >= 5.015002 || ("$]" >= 5.014002 && "$]" < 5.015) ||
	    ("$]" >= 5.012005 && "$]" < 5.013)) {
	*CALLER_OVERRIDE_CHECK_OK = sub () { 1 };
    } else {
	*CALLER_OVERRIDE_CHECK_OK = sub () { 0 };
    }
}

sub caller_info {
    my $i = shift(@_) + 1;
    my %call_info;
    my $cgc = _cgc();
    {
	# Some things override caller() but forget to implement the
	# @DB::args part of it, which we need.  We check for this by
	# pre-populating @DB::args with a sentinel which no-one else
	# has the address of, so that we can detect whether @DB::args
	# has been properly populated.  However, on earlier versions
	# of perl this check tickles a bug in CORE::caller() which
	# leaks memory.  So we only check on fixed perls.
        @DB::args = \$i if CALLER_OVERRIDE_CHECK_OK;
        package DB;
        @call_info{
            qw(pack file line sub has_args wantarray evaltext is_require) }
            = $cgc ? $cgc->($i) : caller($i);
    }

    unless ( defined $call_info{file} ) {
        return ();
    }

    my $sub_name = Carp::get_subname( \%call_info );
    if ( $call_info{has_args} ) {
        # Guard our serialization of the stack from stack refcounting bugs
        # NOTE this is NOT a complete solution, we cannot 100% guard against
        # these bugs.  However in many cases Perl *is* capable of detecting
        # them and throws an error when it does.  Unfortunately serializing
        # the arguments on the stack is a perfect way of finding these bugs,
        # even when they would not affect normal program flow that did not
        # poke around inside the stack.  Inside of Carp.pm it makes little
        # sense reporting these bugs, as Carp's job is to report the callers
        # errors, not the ones it might happen to tickle while doing so.
        # See: https://rt.perl.org/Public/Bug/Display.html?id=131046
        # and: https://rt.perl.org/Public/Bug/Display.html?id=52610
        # for more details and discussion. - Yves
        my @args = map {
                my $arg;
                local $@= $@;
                eval {
                    $arg = $_;
                    1;
                } or do {
                    $arg = '** argument not available anymore **';
                };
                $arg;
            } @DB::args;
        if (CALLER_OVERRIDE_CHECK_OK && @args == 1
            && ref $args[0] eq ref \$i
            && $args[0] == \$i ) {
            @args = ();    # Don't let anyone see the address of $i
            local $@;
            my $where = eval {
                my $func    = $cgc or return '';
                my $gv      =
                    (_fetch_sub B => 'svref_2object' or return '')
                        ->($func)->GV;
                my $package = $gv->STASH->NAME;
                my $subname = $gv->NAME;
                return unless defined $package && defined $subname;

                # returning CORE::GLOBAL::caller isn't useful for tracing the cause:
                return if $package eq 'CORE::GLOBAL' && $subname eq 'caller';
                " in &${package}::$subname";
            } || '';
            @args
                = "** Incomplete caller override detected$where; \@DB::args were not set **";
        }
        else {
            my $overflow;
            if ( $MaxArgNums and @args > $MaxArgNums )
            {    # More than we want to show?
                $#args = $MaxArgNums - 1;
                $overflow = 1;
            }

            @args = map { Carp::format_arg($_) } @args;

            if ($overflow) {
                push @args, '...';
            }
        }

        # Push the args onto the subroutine
        $sub_name .= '(' . join( ', ', @args ) . ')';
    }
    $call_info{sub_name} = $sub_name;
    return wantarray() ? %call_info : \%call_info;
}

# Transform an argument to a function into a string.
our $in_recurse;
sub format_arg {
    my $arg = shift;

    if ( my $pack= ref($arg) ) {

         # legitimate, let's not leak it.
        if (!$in_recurse && _maybe_isa( $arg, 'UNIVERSAL' ) &&
	    do {
                local $@;
	        local $in_recurse = 1;
		local $SIG{__DIE__} = sub{};
                eval {$arg->can('CARP_TRACE') }
            })
        {
            return $arg->CARP_TRACE();
        }
        elsif (!$in_recurse &&
	       defined($RefArgFormatter) &&
	       do {
                local $@;
	        local $in_recurse = 1;
		local $SIG{__DIE__} = sub{};
                eval {$arg = $RefArgFormatter->($arg); 1}
                })
        {
            return $arg;
        }
        else
        {
            # Argument may be blessed into a class with overloading, and so
            # might have an overloaded stringification.  We don't want to
            # risk getting the overloaded stringification, so we need to
            # use _StrVal, our overload::StrVal()-equivalent.
            return _StrVal $arg;
        }
    }
    return "undef" if !defined($arg);
    downgrade($arg, 1);
    return $arg if !(UTF8_REGEXP_PROBLEM && is_utf8($arg)) &&
	    $arg =~ /\A-?[0-9]+(?:\.[0-9]*)?(?:[eE][-+]?[0-9]+)?\z/;
    my $suffix = "";
    if ( 2 < $MaxArgLen and $MaxArgLen < length($arg) ) {
        substr ( $arg, $MaxArgLen - 3 ) = "";
	$suffix = "...";
    }
    if(UTF8_REGEXP_PROBLEM && is_utf8($arg)) {
	for(my $i = length($arg); $i--; ) {
	    my $c = substr($arg, $i, 1);
	    my $x = substr($arg, 0, 0);   # work around bug on Perl 5.8.{1,2}
	    if($c eq "\"" || $c eq "\\" || $c eq "\$" || $c eq "\@") {
		substr $arg, $i, 0, "\\";
		next;
	    }
	    my $o = ord($c);
	    substr $arg, $i, 1, sprintf("\\x{%x}", $o)
		unless is_safe_printable_codepoint($o);
	}
    } else {
	$arg =~ s/([\"\\\$\@])/\\$1/g;
        # This is all the ASCII printables spelled-out.  It is portable to all
        # Perl versions and platforms (such as EBCDIC).  There are other more
        # compact ways to do this, but may not work everywhere every version.
        $arg =~ s/([^ !"#\$\%\&'()*+,\-.\/0123456789:;<=>?\@ABCDEFGHIJKLMNOPQRSTUVWXYZ\[\\\]^_`abcdefghijklmnopqrstuvwxyz\{|}~])/sprintf("\\x{%x}",ord($1))/eg;
    }
    downgrade($arg, 1);
    return "\"".$arg."\"".$suffix;
}

sub Regexp::CARP_TRACE {
    my $arg = "$_[0]";
    downgrade($arg, 1);
    if(UTF8_REGEXP_PROBLEM && is_utf8($arg)) {
	for(my $i = length($arg); $i--; ) {
	    my $o = ord(substr($arg, $i, 1));
	    my $x = substr($arg, 0, 0);   # work around bug on Perl 5.8.{1,2}
	    substr $arg, $i, 1, sprintf("\\x{%x}", $o)
		unless is_safe_printable_codepoint($o);
	}
    } else {
        # See comment in format_arg() about this same regex.
        $arg =~ s/([^ !"#\$\%\&'()*+,\-.\/0123456789:;<=>?\@ABCDEFGHIJKLMNOPQRSTUVWXYZ\[\\\]^_`abcdefghijklmnopqrstuvwxyz\{|}~])/sprintf("\\x{%x}",ord($1))/eg;
    }
    downgrade($arg, 1);
    my $suffix = "";
    if($arg =~ /\A\(\?\^?([a-z]*)(?:-[a-z]*)?:(.*)\)\z/s) {
	($suffix, $arg) = ($1, $2);
    }
    if ( 2 < $MaxArgLen and $MaxArgLen < length($arg) ) {
        substr ( $arg, $MaxArgLen - 3 ) = "";
	$suffix = "...".$suffix;
    }
    return "qr($arg)$suffix";
}

# Takes an inheritance cache and a package and returns
# an anon hash of known inheritances and anon array of
# inheritances which consequences have not been figured
# for.
sub get_status {
    my $cache = shift;
    my $pkg   = shift;
    $cache->{$pkg} ||= [ { $pkg => $pkg }, [ trusts_directly($pkg) ] ];
    return @{ $cache->{$pkg} };
}

# Takes the info from caller() and figures out the name of
# the sub/require/eval
sub get_subname {
    my $info = shift;
    if ( defined( $info->{evaltext} ) ) {
        my $eval = $info->{evaltext};
        if ( $info->{is_require} ) {
            return "require $eval";
        }
        else {
            $eval =~ s/([\\\'])/\\$1/g;
            return "eval '" . str_len_trim( $eval, $MaxEvalLen ) . "'";
        }
    }

    # this can happen on older perls when the sub (or the stash containing it)
    # has been deleted
    if ( !defined( $info->{sub} ) ) {
        return '__ANON__::__ANON__';
    }

    return ( $info->{sub} eq '(eval)' ) ? 'eval {...}' : $info->{sub};
}

# Figures out what call (from the point of view of the caller)
# the long error backtrace should start at.
sub long_error_loc {
    my $i;
    my $lvl = $CarpLevel;
    {
        ++$i;
        my $cgc = _cgc();
        my @caller = $cgc ? $cgc->($i) : caller($i);
        my $pkg = $caller[0];
        unless ( defined($pkg) ) {

            # This *shouldn't* happen.
            if (%Internal) {
                local %Internal;
                $i = long_error_loc();
                last;
            }
            elsif (defined $caller[2]) {
                # this can happen when the stash has been deleted
                # in that case, just assume that it's a reasonable place to
                # stop (the file and line data will still be intact in any
                # case) - the only issue is that we can't detect if the
                # deleted package was internal (so don't do that then)
                # -doy
                redo unless 0 > --$lvl;
                last;
            }
            else {
                return 2;
            }
        }
        redo if $CarpInternal{$pkg};
        redo unless 0 > --$lvl;
        redo if $Internal{$pkg};
    }
    return $i - 1;
}

sub longmess_heavy {
    if ( ref( $_[0] ) ) {   # don't break references as exceptions
        return wantarray ? @_ : $_[0];
    }
    my $i = long_error_loc();
    return ret_backtrace( $i, @_ );
}

BEGIN {
    if("$]" >= 5.017004) {
        # The LAST_FH constant is a reference to the variable.
        $Carp::{LAST_FH} = \eval '\${^LAST_FH}';
    } else {
        eval '*LAST_FH = sub () { 0 }';
    }
}

# Returns a full stack backtrace starting from where it is
# told.
sub ret_backtrace {
    my ( $i, @error ) = @_;
    my $mess;
    my $err = join '', @error;
    $i++;

    my $tid_msg = '';
    if ( defined &threads::tid ) {
        my $tid = threads->tid;
        $tid_msg = " thread $tid" if $tid;
    }

    my %i = caller_info($i);
    $mess = "$err at $i{file} line $i{line}$tid_msg";
    if( $. ) {
      # Use ${^LAST_FH} if available.
      if (LAST_FH) {
        if (${+LAST_FH}) {
            $mess .= sprintf ", <%s> %s %d",
                              *${+LAST_FH}{NAME},
                              ($/ eq "\n" ? "line" : "chunk"), $.
        }
      }
      else {
        local $@ = '';
        local $SIG{__DIE__};
        eval {
            CORE::die;
        };
        if($@ =~ /^Died at .*(, <.*?> (?:line|chunk) \d+).$/ ) {
            $mess .= $1;
        }
      }
    }
    $mess .= "\.\n";

    while ( my %i = caller_info( ++$i ) ) {
        $mess .= "\t$i{sub_name} called at $i{file} line $i{line}$tid_msg\n";
    }

    return $mess;
}

sub ret_summary {
    my ( $i, @error ) = @_;
    my $err = join '', @error;
    $i++;

    my $tid_msg = '';
    if ( defined &threads::tid ) {
        my $tid = threads->tid;
        $tid_msg = " thread $tid" if $tid;
    }

    my %i = caller_info($i);
    return "$err at $i{file} line $i{line}$tid_msg\.\n";
}

sub short_error_loc {
    # You have to create your (hash)ref out here, rather than defaulting it
    # inside trusts *on a lexical*, as you want it to persist across calls.
    # (You can default it on $_[2], but that gets messy)
    my $cache = {};
    my $i     = 1;
    my $lvl   = $CarpLevel;
    {
        my $cgc = _cgc();
        my $called = $cgc ? $cgc->($i) : caller($i);
        $i++;
        my $caller = $cgc ? $cgc->($i) : caller($i);

        if (!defined($caller)) {
            my @caller = $cgc ? $cgc->($i) : caller($i);
            if (@caller) {
                # if there's no package but there is other caller info, then
                # the package has been deleted - treat this as a valid package
                # in this case
                redo if defined($called) && $CarpInternal{$called};
                redo unless 0 > --$lvl;
                last;
            }
            else {
                return 0;
            }
        }
        redo if $Internal{$caller};
        redo if $CarpInternal{$caller};
        redo if $CarpInternal{$called};
        redo if trusts( $called, $caller, $cache );
        redo if trusts( $caller, $called, $cache );
        redo unless 0 > --$lvl;
    }
    return $i - 1;
}

sub shortmess_heavy {
    return longmess_heavy(@_) if $Verbose;
    return @_ if ref( $_[0] );    # don't break references as exceptions
    my $i = short_error_loc();
    if ($i) {
        ret_summary( $i, @_ );
    }
    else {
        longmess_heavy(@_);
    }
}

# If a string is too long, trims it with ...
sub str_len_trim {
    my $str = shift;
    my $max = shift || 0;
    if ( 2 < $max and $max < length($str) ) {
        substr( $str, $max - 3 ) = '...';
    }
    return $str;
}

# Takes two packages and an optional cache.  Says whether the
# first inherits from the second.
#
# Recursive versions of this have to work to avoid certain
# possible endless loops, and when following long chains of
# inheritance are less efficient.
sub trusts {
    my $child  = shift;
    my $parent = shift;
    my $cache  = shift;
    my ( $known, $partial ) = get_status( $cache, $child );

    # Figure out consequences until we have an answer
    while ( @$partial and not exists $known->{$parent} ) {
        my $anc = shift @$partial;
        next if exists $known->{$anc};
        $known->{$anc}++;
        my ( $anc_knows, $anc_partial ) = get_status( $cache, $anc );
        my @found = keys %$anc_knows;
        @$known{@found} = ();
        push @$partial, @$anc_partial;
    }
    return exists $known->{$parent};
}

# Takes a package and gives a list of those trusted directly
sub trusts_directly {
    my $class = shift;
    no strict 'refs';
    my $stash = \%{"$class\::"};
    for my $var (qw/ CARP_NOT ISA /) {
        # Don't try using the variable until we know it exists,
        # to avoid polluting the caller's namespace.
        if ( $stash->{$var} && ref \$stash->{$var} eq 'GLOB'
          && *{$stash->{$var}}{ARRAY} && @{$stash->{$var}} ) {
           return @{$stash->{$var}}
        }
    }
    return;
}

if(!defined($warnings::VERSION) ||
	do { no warnings "numeric"; $warnings::VERSION < 1.03 }) {
    # Very old versions of warnings.pm import from Carp.  This can go
    # wrong due to the circular dependency.  If Carp is invoked before
    # warnings, then Carp starts by loading warnings, then warnings
    # tries to import from Carp, and gets nothing because Carp is in
    # the process of loading and hasn't defined its import method yet.
    # So we work around that by manually exporting to warnings here.
    no strict "refs";
    *{"warnings::$_"} = \&$_ foreach @EXPORT;
}

1;

__END__

=head1 NAME

Carp - alternative warn and die for modules

=head1 SYNOPSIS

    use Carp;

    # warn user (from perspective of caller)
    carp "string trimmed to 80 chars";

    # die of errors (from perspective of caller)
    croak "We're outta here!";

    # die of errors with stack backtrace
    confess "not implemented";

    # cluck, longmess and shortmess not exported by default
    use Carp qw(cluck longmess shortmess);
    cluck "This is how we got here!"; # warn with stack backtrace
    $long_message   = longmess( "message from cluck() or confess()" );
    $short_message  = shortmess( "message from carp() or croak()" );

=head1 DESCRIPTION

The Carp routines are useful in your own modules because
they act like C<die()> or C<warn()>, but with a message which is more
likely to be useful to a user of your module.  In the case of
C<cluck()> and C<confess()>, that context is a summary of every
call in the call-stack; C<longmess()> returns the contents of the error
message.

For a shorter message you can use C<carp()> or C<croak()> which report the
error as being from where your module was called.  C<shortmess()> returns the
contents of this error message.  There is no guarantee that that is where the
error was, but it is a good educated guess.

C<Carp> takes care not to clobber the status variables C<$!> and C<$^E>
in the course of assembling its error messages.  This means that a
C<$SIG{__DIE__}> or C<$SIG{__WARN__}> handler can capture the error
information held in those variables, if it is required to augment the
error message, and if the code calling C<Carp> left useful values there.
Of course, C<Carp> can't guarantee the latter.

You can also alter the way the output and logic of C<Carp> works, by
changing some global variables in the C<Carp> namespace. See the
section on C<GLOBAL VARIABLES> below.

Here is a more complete description of how C<carp> and C<croak> work.
What they do is search the call-stack for a function call stack where
they have not been told that there shouldn't be an error.  If every
call is marked safe, they give up and give a full stack backtrace
instead.  In other words they presume that the first likely looking
potential suspect is guilty.  Their rules for telling whether
a call shouldn't generate errors work as follows:

=over 4

=item 1.

Any call from a package to itself is safe.

=item 2.

Packages claim that there won't be errors on calls to or from
packages explicitly marked as safe by inclusion in C<@CARP_NOT>, or
(if that array is empty) C<@ISA>.  The ability to override what
@ISA says is new in 5.8.

=item 3.

The trust in item 2 is transitive.  If A trusts B, and B
trusts C, then A trusts C.  So if you do not override C<@ISA>
with C<@CARP_NOT>, then this trust relationship is identical to,
"inherits from".

=item 4.

Any call from an internal Perl module is safe.  (Nothing keeps
user modules from marking themselves as internal to Perl, but
this practice is discouraged.)

=item 5.

Any call to Perl's warning system (eg Carp itself) is safe.
(This rule is what keeps it from reporting the error at the
point where you call C<carp> or C<croak>.)

=item 6.

C<$Carp::CarpLevel> can be set to skip a fixed number of additional
call levels.  Using this is not recommended because it is very
difficult to get it to behave correctly.

=back

=head2 Forcing a Stack Trace

As a debugging aid, you can force Carp to treat a croak as a confess
and a carp as a cluck across I<all> modules. In other words, force a
detailed stack trace to be given.  This can be very helpful when trying
to understand why, or from where, a warning or error is being generated.

This feature is enabled by 'importing' the non-existent symbol
'verbose'. You would typically enable it by saying

    perl -MCarp=verbose script.pl

or by including the string C<-MCarp=verbose> in the PERL5OPT
environment variable.

Alternately, you can set the global variable C<$Carp::Verbose> to true.
See the C<GLOBAL VARIABLES> section below.

=head2 Stack Trace formatting

At each stack level, the subroutine's name is displayed along with
its parameters.  For simple scalars, this is sufficient.  For complex
data types, such as objects and other references, this can simply
display C<'HASH(0x1ab36d8)'>.

Carp gives two ways to control this.

=over 4

=item 1.

For objects, a method, C<CARP_TRACE>, will be called, if it exists.  If
this method doesn't exist, or it recurses into C<Carp>, or it otherwise
throws an exception, this is skipped, and Carp moves on to the next option,
otherwise checking stops and the string returned is used.  It is recommended
that the object's type is part of the string to make debugging easier.

=item 2.

For any type of reference, C<$Carp::RefArgFormatter> is checked (see below).
This variable is expected to be a code reference, and the current parameter
is passed in.  If this function doesn't exist (the variable is undef), or
it recurses into C<Carp>, or it otherwise throws an exception, this is
skipped, and Carp moves on to the next option, otherwise checking stops
and the string returned is used.

=item 3.

Otherwise, if neither C<CARP_TRACE> nor C<$Carp::RefArgFormatter> is
available, stringify the value ignoring any overloading.

=back

=head1 GLOBAL VARIABLES

=head2 $Carp::MaxEvalLen

This variable determines how many characters of a string-eval are to
be shown in the output. Use a value of C<0> to show all text.

Defaults to C<0>.

=head2 $Carp::MaxArgLen

This variable determines how many characters of each argument to a
function to print. Use a value of C<0> to show the full length of the
argument.

Defaults to C<64>.

=head2 $Carp::MaxArgNums

This variable determines how many arguments to each function to show.
Use a false value to show all arguments to a function call.  To suppress all
arguments, use C<-1> or C<'0 but true'>.

Defaults to C<8>.

=head2 $Carp::Verbose

This variable makes C<carp()> and C<croak()> generate stack backtraces
just like C<cluck()> and C<confess()>.  This is how C<use Carp 'verbose'>
is implemented internally.

Defaults to C<0>.

=head2 $Carp::RefArgFormatter

This variable sets a general argument formatter to display references.
Plain scalars and objects that implement C<CARP_TRACE> will not go through
this formatter.  Calling C<Carp> from within this function is not supported.

local $Carp::RefArgFormatter = sub {
    require Data::Dumper;
    Data::Dumper::Dump($_[0]); # not necessarily safe
};

=head2 @CARP_NOT

This variable, I<in your package>, says which packages are I<not> to be
considered as the location of an error. The C<carp()> and C<cluck()>
functions will skip over callers when reporting where an error occurred.

NB: This variable must be in the package's symbol table, thus:

    # These work
    our @CARP_NOT; # file scope
    use vars qw(@CARP_NOT); # package scope
    @My::Package::CARP_NOT = ... ; # explicit package variable

    # These don't work
    sub xyz { ... @CARP_NOT = ... } # w/o declarations above
    my @CARP_NOT; # even at top-level

Example of use:

    package My::Carping::Package;
    use Carp;
    our @CARP_NOT;
    sub bar     { .... or _error('Wrong input') }
    sub _error  {
        # temporary control of where'ness, __PACKAGE__ is implicit
        local @CARP_NOT = qw(My::Friendly::Caller);
        carp(@_)
    }

This would make C<Carp> report the error as coming from a caller not
in C<My::Carping::Package>, nor from C<My::Friendly::Caller>.

Also read the L</DESCRIPTION> section above, about how C<Carp> decides
where the error is reported from.

Use C<@CARP_NOT>, instead of C<$Carp::CarpLevel>.

Overrides C<Carp>'s use of C<@ISA>.

=head2 %Carp::Internal

This says what packages are internal to Perl.  C<Carp> will never
report an error as being from a line in a package that is internal to
Perl.  For example:

    $Carp::Internal{ (__PACKAGE__) }++;
    # time passes...
    sub foo { ... or confess("whatever") };

would give a full stack backtrace starting from the first caller
outside of __PACKAGE__.  (Unless that package was also internal to
Perl.)

=head2 %Carp::CarpInternal

This says which packages are internal to Perl's warning system.  For
generating a full stack backtrace this is the same as being internal
to Perl, the stack backtrace will not start inside packages that are
listed in C<%Carp::CarpInternal>.  But it is slightly different for
the summary message generated by C<carp> or C<croak>.  There errors
will not be reported on any lines that are calling packages in
C<%Carp::CarpInternal>.

For example C<Carp> itself is listed in C<%Carp::CarpInternal>.
Therefore the full stack backtrace from C<confess> will not start
inside of C<Carp>, and the short message from calling C<croak> is
not placed on the line where C<croak> was called.

=head2 $Carp::CarpLevel

This variable determines how many additional call frames are to be
skipped that would not otherwise be when reporting where an error
occurred on a call to one of C<Carp>'s functions.  It is fairly easy
to count these call frames on calls that generate a full stack
backtrace.  However it is much harder to do this accounting for calls
that generate a short message.  Usually people skip too many call
frames.  If they are lucky they skip enough that C<Carp> goes all of
the way through the call stack, realizes that something is wrong, and
then generates a full stack backtrace.  If they are unlucky then the
error is reported from somewhere misleading very high in the call
stack.

Therefore it is best to avoid C<$Carp::CarpLevel>.  Instead use
C<@CARP_NOT>, C<%Carp::Internal> and C<%Carp::CarpInternal>.

Defaults to C<0>.

=head1 BUGS

The Carp routines don't handle exception objects currently.
If called with a first argument that is a reference, they simply
call die() or warn(), as appropriate.

=head1 SEE ALSO

L<Carp::Always>,
L<Carp::Clan>

=head1 CONTRIBUTING

L<Carp> is maintained by the perl 5 porters as part of the core perl 5
version control repository. Please see the L<perlhack> perldoc for how to
submit patches and contribute to it.

=head1 AUTHOR

The Carp module first appeared in Larry Wall's perl 5.000 distribution.
Since then it has been modified by several of the perl 5 porters.
Andrew Main (Zefram) <zefram@fysh.org> divested Carp into an independent
distribution.

=head1 COPYRIGHT

Copyright (C) 1994-2013 Larry Wall

Copyright (C) 2011, 2012, 2013 Andrew Main (Zefram) <zefram@fysh.org>

=head1 LICENSE

This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.