xref: /openbsd/gnu/usr.bin/perl/lib/diagnostics.pm (revision 097a140d) 
1package diagnostics;
2
3=head1 NAME
4
5diagnostics, splain - produce verbose warning diagnostics
6
7=head1 SYNOPSIS
8
9Using the C<diagnostics> pragma:
10
11    use diagnostics;
12    use diagnostics -verbose;
13
14    enable  diagnostics;
15    disable diagnostics;
16
17Using the C<splain> standalone filter program:
18
19    perl program 2>diag.out
20    splain [-v] [-p] diag.out
21
22Using diagnostics to get stack traces from a misbehaving script:
23
24    perl -Mdiagnostics=-traceonly my_script.pl
25
26=head1 DESCRIPTION
27
28=head2 The C<diagnostics> Pragma
29
30This module extends the terse diagnostics normally emitted by both the
31perl compiler and the perl interpreter (from running perl with a -w
32switch or C<use warnings>), augmenting them with the more
33explicative and endearing descriptions found in L<perldiag>.  Like the
34other pragmata, it affects the compilation phase of your program rather
35than merely the execution phase.
36
37To use in your program as a pragma, merely invoke
38
39    use diagnostics;
40
41at the start (or near the start) of your program.  (Note
42that this I<does> enable perl's B<-w> flag.)  Your whole
43compilation will then be subject(ed :-) to the enhanced diagnostics.
44These still go out B<STDERR>.
45
46Due to the interaction between runtime and compiletime issues,
47and because it's probably not a very good idea anyway,
48you may not use C<no diagnostics> to turn them off at compiletime.
49However, you may control their behaviour at runtime using the
50disable() and enable() methods to turn them off and on respectively.
51
52The B<-verbose> flag first prints out the L<perldiag> introduction before
53any other diagnostics.  The $diagnostics::PRETTY variable can generate nicer
54escape sequences for pagers.
55
56Warnings dispatched from perl itself (or more accurately, those that match
57descriptions found in L<perldiag>) are only displayed once (no duplicate
58descriptions).  User code generated warnings a la warn() are unaffected,
59allowing duplicate user messages to be displayed.
60
61This module also adds a stack trace to the error message when perl dies.
62This is useful for pinpointing what
63caused the death.  The B<-traceonly> (or
64just B<-t>) flag turns off the explanations of warning messages leaving just
65the stack traces.  So if your script is dieing, run it again with
66
67  perl -Mdiagnostics=-traceonly my_bad_script
68
69to see the call stack at the time of death.  By supplying the B<-warntrace>
70(or just B<-w>) flag, any warnings emitted will also come with a stack
71trace.
72
73=head2 The I<splain> Program
74
75While apparently a whole nuther program, I<splain> is actually nothing
76more than a link to the (executable) F<diagnostics.pm> module, as well as
77a link to the F<diagnostics.pod> documentation.  The B<-v> flag is like
78the C<use diagnostics -verbose> directive.
79The B<-p> flag is like the
80$diagnostics::PRETTY variable.  Since you're post-processing with
81I<splain>, there's no sense in being able to enable() or disable() processing.
82
83Output from I<splain> is directed to B<STDOUT>, unlike the pragma.
84
85=head1 EXAMPLES
86
87The following file is certain to trigger a few errors at both
88runtime and compiletime:
89
90    use diagnostics;
91    print NOWHERE "nothing\n";
92    print STDERR "\n\tThis message should be unadorned.\n";
93    warn "\tThis is a user warning";
94    print "\nDIAGNOSTIC TESTER: Please enter a <CR> here: ";
95    my $a, $b = scalar <STDIN>;
96    print "\n";
97    print $x/$y;
98
99If you prefer to run your program first and look at its problem
100afterwards, do this:
101
102    perl -w test.pl 2>test.out
103    ./splain < test.out
104
105Note that this is not in general possible in shells of more dubious heritage,
106as the theoretical
107
108    (perl -w test.pl >/dev/tty) >& test.out
109    ./splain < test.out
110
111Because you just moved the existing B<stdout> to somewhere else.
112
113If you don't want to modify your source code, but still have on-the-fly
114warnings, do this:
115
116    exec 3>&1; perl -w test.pl 2>&1 1>&3 3>&- | splain 1>&2 3>&-
117
118Nifty, eh?
119
120If you want to control warnings on the fly, do something like this.
121Make sure you do the C<use> first, or you won't be able to get
122at the enable() or disable() methods.
123
124    use diagnostics; # checks entire compilation phase
125	print "\ntime for 1st bogus diags: SQUAWKINGS\n";
126	print BOGUS1 'nada';
127	print "done with 1st bogus\n";
128
129    disable diagnostics; # only turns off runtime warnings
130	print "\ntime for 2nd bogus: (squelched)\n";
131	print BOGUS2 'nada';
132	print "done with 2nd bogus\n";
133
134    enable diagnostics; # turns back on runtime warnings
135	print "\ntime for 3rd bogus: SQUAWKINGS\n";
136	print BOGUS3 'nada';
137	print "done with 3rd bogus\n";
138
139    disable diagnostics;
140	print "\ntime for 4th bogus: (squelched)\n";
141	print BOGUS4 'nada';
142	print "done with 4th bogus\n";
143
144=head1 INTERNALS
145
146Diagnostic messages derive from the F<perldiag.pod> file when available at
147runtime.  Otherwise, they may be embedded in the file itself when the
148splain package is built.   See the F<Makefile> for details.
149
150If an extant $SIG{__WARN__} handler is discovered, it will continue
151to be honored, but only after the diagnostics::splainthis() function
152(the module's $SIG{__WARN__} interceptor) has had its way with your
153warnings.
154
155There is a $diagnostics::DEBUG variable you may set if you're desperately
156curious what sorts of things are being intercepted.
157
158    BEGIN { $diagnostics::DEBUG = 1 }
159
160
161=head1 BUGS
162
163Not being able to say "no diagnostics" is annoying, but may not be
164insurmountable.
165
166The C<-pretty> directive is called too late to affect matters.
167You have to do this instead, and I<before> you load the module.
168
169    BEGIN { $diagnostics::PRETTY = 1 }
170
171I could start up faster by delaying compilation until it should be
172needed, but this gets a "panic: top_level" when using the pragma form
173in Perl 5.001e.
174
175While it's true that this documentation is somewhat subserious, if you use
176a program named I<splain>, you should expect a bit of whimsy.
177
178=head1 AUTHOR
179
180Tom Christiansen <F<tchrist@mox.perl.com>>, 25 June 1995.
181
182=cut
183
184use strict;
185use 5.009001;
186use Carp;
187$Carp::Internal{__PACKAGE__.""}++;
188
189our $VERSION = '1.37';
190our $DEBUG;
191our $VERBOSE;
192our $PRETTY;
193our $TRACEONLY = 0;
194our $WARNTRACE = 0;
195
196use Config;
197use Text::Tabs 'expand';
198my $privlib = $Config{privlibexp};
199if ($^O eq 'VMS') {
200    require VMS::Filespec;
201    $privlib = VMS::Filespec::unixify($privlib);
202}
203my @trypod = (
204	   "$privlib/pod/perldiag.pod",
205	   "$privlib/pods/perldiag.pod",
206	  );
207# handy for development testing of new warnings etc
208unshift @trypod, "./pod/perldiag.pod" if -e "pod/perldiag.pod";
209(my $PODFILE) = ((grep { -e } @trypod), $trypod[$#trypod])[0];
210
211$DEBUG ||= 0;
212
213local $| = 1;
214local $_;
215local $.;
216
217my $standalone;
218my(%HTML_2_Troff, %HTML_2_Latin_1, %HTML_2_ASCII_7);
219
220CONFIG: {
221    our $opt_p = our $opt_d = our $opt_v = our $opt_f = '';
222
223    unless (caller) {
224	$standalone++;
225	require Getopt::Std;
226	Getopt::Std::getopts('pdvf:')
227	    or die "Usage: $0 [-v] [-p] [-f splainpod]";
228	$PODFILE = $opt_f if $opt_f;
229	$DEBUG = 2 if $opt_d;
230	$VERBOSE = $opt_v;
231	$PRETTY = $opt_p;
232    }
233
234    if (open(POD_DIAG, '<', $PODFILE)) {
235	warn "Happy happy podfile from real $PODFILE\n" if $DEBUG;
236	last CONFIG;
237    }
238
239    if (caller) {
240	INCPATH: {
241	    for my $file ( (map { "$_/".__PACKAGE__.".pm" } @INC), $0) {
242		warn "Checking $file\n" if $DEBUG;
243		if (open(POD_DIAG, '<', $file)) {
244		    while (<POD_DIAG>) {
245			next unless
246			    /^__END__\s*# wish diag dbase were more accessible/;
247			print STDERR "podfile is $file\n" if $DEBUG;
248			last INCPATH;
249		    }
250		}
251	    }
252	}
253    } else {
254	print STDERR "podfile is <DATA>\n" if $DEBUG;
255	*POD_DIAG = *main::DATA;
256    }
257}
258if (eof(POD_DIAG)) {
259    die "couldn't find diagnostic data in $PODFILE @INC $0";
260}
261
262
263%HTML_2_Troff = (
264    'amp'	=>	'&',	#   ampersand
265    'lt'	=>	'<',	#   left chevron, less-than
266    'gt'	=>	'>',	#   right chevron, greater-than
267    'quot'	=>	'"',	#   double quote
268    'sol'	=>	'/',	#   forward slash / solidus
269    'verbar'    =>	'|',	#   vertical bar
270
271    "Aacute"	=>	"A\\*'",	#   capital A, acute accent
272    # etc
273
274);
275
276%HTML_2_Latin_1 = (
277    'amp'	=>	'&',	#   ampersand
278    'lt'	=>	'<',	#   left chevron, less-than
279    'gt'	=>	'>',	#   right chevron, greater-than
280    'quot'	=>	'"',	#   double quote
281    'sol'	=>	'/',	#   Forward slash / solidus
282    'verbar'    =>	'|',	#   vertical bar
283
284    "Aacute"	=>	"\xC1"	#   capital A, acute accent
285
286    # etc
287);
288
289%HTML_2_ASCII_7 = (
290    'amp'	=>	'&',	#   ampersand
291    'lt'	=>	'<',	#   left chevron, less-than
292    'gt'	=>	'>',	#   right chevron, greater-than
293    'quot'	=>	'"',	#   double quote
294    'sol'	=>	'/',	#   Forward slash / solidus
295    'verbar'    =>	'|',	#   vertical bar
296
297    "Aacute"	=>	"A"	#   capital A, acute accent
298    # etc
299);
300
301our %HTML_Escapes;
302*HTML_Escapes = do {
303    if ($standalone) {
304	$PRETTY ? \%HTML_2_Latin_1 : \%HTML_2_ASCII_7;
305    } else {
306	\%HTML_2_Latin_1;
307    }
308};
309
310*THITHER = $standalone ? *STDOUT : *STDERR;
311
312my %transfmt = ();
313my $transmo = <<EOFUNC;
314sub transmo {
315    #local \$^W = 0;  # recursive warnings we do NOT need!
316EOFUNC
317
318my %msg;
319my $over_level = 0;     # We look only at =item lines at the first =over level
320{
321    print STDERR "FINISHING COMPILATION for $_\n" if $DEBUG;
322    local $/ = '';
323    local $_;
324    my $header;
325    my @headers;
326    my $for_item;
327    my $seen_body;
328    while (<POD_DIAG>) {
329
330	sub _split_pod_link {
331	    $_[0] =~ m'(?:([^|]*)\|)?([^/]*)(?:/("?)(.*)\3)?'s;
332	    ($1,$2,$4);
333	}
334
335	unescape();
336	if ($PRETTY) {
337	    sub noop   { return $_[0] }  # spensive for a noop
338	    sub bold   { my $str =$_[0];  $str =~ s/(.)/$1\b$1/g; return $str; }
339	    sub italic { my $str = $_[0]; $str =~ s/(.)/_\b$1/g;  return $str; }
340	    s/C<<< (.*?) >>>|C<< (.*?) >>|[BC]<(.*?)>/bold($+)/ges;
341	    s/[IF]<(.*?)>/italic($1)/ges;
342	    s/L<(.*?)>/
343	       my($text,$page,$sect) = _split_pod_link($1);
344	       defined $text
345	        ? $text
346	        : defined $sect
347	           ? italic($sect) . ' in ' . italic($page)
348	           : italic($page)
349	     /ges;
350	     s/S<(.*?)>/
351               $1
352             /ges;
353	} else {
354	    s/C<<< (.*?) >>>|C<< (.*?) >>|[BC]<(.*?)>/$+/gs;
355	    s/[IF]<(.*?)>/$1/gs;
356	    s/L<(.*?)>/
357	       my($text,$page,$sect) = _split_pod_link($1);
358	       defined $text
359	        ? $text
360	        : defined $sect
361	           ? qq '"$sect" in $page'
362	           : $page
363	     /ges;
364	    s/S<(.*?)>/
365               $1
366             /ges;
367	}
368	unless (/^=/) {
369	    if (defined $header) {
370		if ( $header eq 'DESCRIPTION' &&
371		    (   /Optional warnings are enabled/
372		     || /Some of these messages are generic./
373		    ) )
374		{
375		    next;
376		}
377		$_ = expand $_;
378		s/^/    /gm;
379		$msg{$header} .= $_;
380		for my $h(@headers) { $msg{$h} .= $_ }
381		++$seen_body;
382	 	undef $for_item;
383	    }
384	    next;
385	}
386
387	# If we have not come across the body of the description yet, then
388	# the previous header needs to share the same description.
389	if ($seen_body) {
390	    @headers = ();
391	}
392	else {
393	    push @headers, $header if defined $header;
394	}
395
396	if ( ! s/=item (.*?)\s*\z//s || $over_level != 1) {
397
398	    if ( s/=head1\sDESCRIPTION//) {
399		$msg{$header = 'DESCRIPTION'} = '';
400		undef $for_item;
401	    }
402	    elsif( s/^=for\s+diagnostics\s*\n(.*?)\s*\z// ) {
403		$for_item = $1;
404	    }
405	    elsif( /^=over\b/ ) {
406                $over_level++;
407            }
408	    elsif( /^=back\b/ ) { # Stop processing body here
409                $over_level--;
410                if ($over_level == 0) {
411                    undef $header;
412                    undef $for_item;
413                    $seen_body = 0;
414                    next;
415                }
416	    }
417	    next;
418	}
419
420	if( $for_item ) { $header = $for_item; undef $for_item }
421	else {
422	    $header = $1;
423
424	    $header =~ s/\n/ /gs; # Allow multi-line headers
425	}
426
427	# strip formatting directives from =item line
428	$header =~ s/[A-Z]<(.*?)>/$1/g;
429
430	# Since we strip "(\.\s*)\n" when we search a warning, strip it here as well
431	$header =~ s/(\.\s*)?$//;
432
433        my @toks = split( /(%l?[dxX]|%[ucp]|%(?:\.\d+)?[fs])/, $header );
434	if (@toks > 1) {
435            my $conlen = 0;
436            for my $i (0..$#toks){
437                if( $i % 2 ){
438                    if(      $toks[$i] eq '%c' ){
439                        $toks[$i] = '.';
440                    } elsif( $toks[$i] =~ /^%(?:d|u)$/ ){
441                        $toks[$i] = '\d+';
442                    } elsif( $toks[$i] =~ '^%(?:s|.*f)$' ){
443                        $toks[$i] = $i == $#toks ? '.*' : '.*?';
444                    } elsif( $toks[$i] =~ '%.(\d+)s' ){
445                        $toks[$i] = ".{$1}";
446                    } elsif( $toks[$i] =~ '^%l*([pxX])$' ){
447                        $toks[$i] = $1 eq 'X' ? '[\dA-F]+' : '[\da-f]+';
448                    }
449                } elsif( length( $toks[$i] ) ){
450                    $toks[$i] = quotemeta $toks[$i];
451                    $conlen += length( $toks[$i] );
452                }
453            }
454            my $lhs = join( '', @toks );
455            $lhs =~ s/(\\\s)+/\\s+/g; # Replace lit space with multi-space match
456	    $transfmt{$header}{pat} =
457              "    s^\\s*$lhs\\s*\Q$header\Es\n\t&& return 1;\n";
458            $transfmt{$header}{len} = $conlen;
459	} else {
460            my $lhs = "\Q$header\E";
461            $lhs =~ s/(\\\s)+/\\s+/g; # Replace lit space with multi-space match
462            $transfmt{$header}{pat} =
463	      "    s^\\s*$lhs\\s*\Q$header\E\n\t && return 1;\n";
464            $transfmt{$header}{len} = length( $header );
465	}
466
467	print STDERR __PACKAGE__.": Duplicate entry: \"$header\"\n"
468	    if $msg{$header};
469
470	$msg{$header} = '';
471	$seen_body = 0;
472    }
473
474
475    close POD_DIAG unless *main::DATA eq *POD_DIAG;
476
477    die "No diagnostics?" unless %msg;
478
479    # Apply patterns in order of decreasing sum of lengths of fixed parts
480    # Seems the best way of hitting the right one.
481    for my $hdr ( sort { $transfmt{$b}{len} <=> $transfmt{$a}{len} }
482                  keys %transfmt ){
483        $transmo .= $transfmt{$hdr}{pat};
484    }
485    $transmo .= "    return 0;\n}\n";
486    print STDERR $transmo if $DEBUG;
487    eval $transmo;
488    die $@ if $@;
489}
490
491if ($standalone) {
492    if (!@ARGV and -t STDIN) { print STDERR "$0: Reading from STDIN\n" }
493    while (defined (my $error = <>)) {
494	splainthis($error) || print THITHER $error;
495    }
496    exit;
497}
498
499my $olddie;
500my $oldwarn;
501
502sub import {
503    shift;
504    $^W = 1; # yup, clobbered the global variable;
505	     # tough, if you want diags, you want diags.
506    return if defined $SIG{__WARN__} && ($SIG{__WARN__} eq \&warn_trap);
507
508    for (@_) {
509
510	/^-d(ebug)?$/ 	   	&& do {
511				    $DEBUG++;
512				    next;
513				   };
514
515	/^-v(erbose)?$/ 	&& do {
516				    $VERBOSE++;
517				    next;
518				   };
519
520	/^-p(retty)?$/ 		&& do {
521				    print STDERR "$0: I'm afraid it's too late for prettiness.\n";
522				    $PRETTY++;
523				    next;
524			       };
525	# matches trace and traceonly for legacy doc mixup reasons
526	/^-t(race(only)?)?$/	&& do {
527				    $TRACEONLY++;
528				    next;
529			       };
530	/^-w(arntrace)?$/ 	&& do {
531				    $WARNTRACE++;
532				    next;
533			       };
534
535	warn "Unknown flag: $_";
536    }
537
538    $oldwarn = $SIG{__WARN__};
539    $olddie = $SIG{__DIE__};
540    $SIG{__WARN__} = \&warn_trap;
541    $SIG{__DIE__} = \&death_trap;
542}
543
544sub enable { &import }
545
546sub disable {
547    shift;
548    return unless $SIG{__WARN__} eq \&warn_trap;
549    $SIG{__WARN__} = $oldwarn || '';
550    $SIG{__DIE__} = $olddie || '';
551}
552
553sub warn_trap {
554    my $warning = $_[0];
555    if (caller eq __PACKAGE__ or !splainthis($warning)) {
556	if ($WARNTRACE) {
557	    print STDERR Carp::longmess($warning);
558	} else {
559	    print STDERR $warning;
560	}
561    }
562    goto &$oldwarn if defined $oldwarn and $oldwarn and $oldwarn ne \&warn_trap;
563};
564
565sub death_trap {
566    my $exception = $_[0];
567
568    # See if we are coming from anywhere within an eval. If so we don't
569    # want to explain the exception because it's going to get caught.
570    my $in_eval = 0;
571    my $i = 0;
572    while (my $caller = (caller($i++))[3]) {
573      if ($caller eq '(eval)') {
574	$in_eval = 1;
575	last;
576      }
577    }
578
579    splainthis($exception) unless $in_eval;
580    if (caller eq __PACKAGE__) {
581	print STDERR "INTERNAL EXCEPTION: $exception";
582    }
583    &$olddie if defined $olddie and $olddie and $olddie ne \&death_trap;
584
585    return if $in_eval;
586
587    # We don't want to unset these if we're coming from an eval because
588    # then we've turned off diagnostics.
589
590    # Switch off our die/warn handlers so we don't wind up in our own
591    # traps.
592    $SIG{__DIE__} = $SIG{__WARN__} = '';
593
594    $exception =~ s/\n(?=.)/\n\t/gas;
595
596    die Carp::longmess("__diagnostics__")
597	  =~ s/^__diagnostics__.*?line \d+\.?\n/
598		  "Uncaught exception from user code:\n\t$exception"
599	      /re;
600	# up we go; where we stop, nobody knows, but i think we die now
601	# but i'm deeply afraid of the &$olddie guy reraising and us getting
602	# into an indirect recursion loop
603};
604
605my %exact_duplicate;
606my %old_diag;
607my $count;
608my $wantspace;
609sub splainthis {
610  return 0 if $TRACEONLY;
611  for (my $tmp = shift) {
612    local $\;
613    local $!;
614    ### &finish_compilation unless %msg;
615    s/(\.\s*)?\n+$//;
616    my $orig = $_;
617    # return unless defined;
618
619    # get rid of the where-are-we-in-input part
620    s/, <.*?> (?:line|chunk).*$//;
621
622    # Discard 1st " at <file> line <no>" and all text beyond
623    # but be aware of messages containing " at this-or-that"
624    my $real = 0;
625    my @secs = split( / at / );
626    return unless @secs;
627    $_ = $secs[0];
628    for my $i ( 1..$#secs ){
629        if( $secs[$i] =~ /.+? (?:line|chunk) \d+/ ){
630            $real = 1;
631            last;
632        } else {
633            $_ .= ' at ' . $secs[$i];
634	}
635    }
636
637    # remove parenthesis occurring at the end of some messages
638    s/^\((.*)\)$/$1/;
639
640    if ($exact_duplicate{$orig}++) {
641	return &transmo;
642    } else {
643	return 0 unless &transmo;
644    }
645
646    my $short = shorten($orig);
647    if ($old_diag{$_}) {
648	autodescribe();
649	print THITHER "$short (#$old_diag{$_})\n";
650	$wantspace = 1;
651    } elsif (!$msg{$_} && $orig =~ /\n./s) {
652	# A multiline message, like "Attempt to reload /
653	# Compilation failed"
654	my $found;
655	for (split /^/, $orig) {
656	    splainthis($_) and $found = 1;
657	}
658	return $found;
659    } else {
660	autodescribe();
661	$old_diag{$_} = ++$count;
662	print THITHER "\n" if $wantspace;
663	$wantspace = 0;
664	print THITHER "$short (#$old_diag{$_})\n";
665	if ($msg{$_}) {
666	    print THITHER $msg{$_};
667	} else {
668	    if (0 and $standalone) {
669		print THITHER "    **** Error #$old_diag{$_} ",
670			($real ? "is" : "appears to be"),
671			" an unknown diagnostic message.\n\n";
672	    }
673	    return 0;
674	}
675    }
676    return 1;
677  }
678}
679
680sub autodescribe {
681    if ($VERBOSE and not $count) {
682	print THITHER &{$PRETTY ? \&bold : \&noop}("DESCRIPTION OF DIAGNOSTICS"),
683		"\n$msg{DESCRIPTION}\n";
684    }
685}
686
687sub unescape {
688    s {
689            E<
690            ( [A-Za-z]+ )
691            >
692    } {
693         do {
694             exists $HTML_Escapes{$1}
695                ? do { $HTML_Escapes{$1} }
696                : do {
697                    warn "Unknown escape: E<$1> in $_";
698                    "E<$1>";
699                }
700         }
701    }egx;
702}
703
704sub shorten {
705    my $line = $_[0];
706    if (length($line) > 79 and index($line, "\n") == -1) {
707	my $space_place = rindex($line, ' ', 79);
708	if ($space_place != -1) {
709	    substr($line, $space_place, 1) = "\n\t";
710	}
711    }
712    return $line;
713}
714
715
7161 unless $standalone;  # or it'll complain about itself
717__END__ # wish diag dbase were more accessible
718