xref: /openbsd/gnu/usr.bin/perl/lib/diagnostics.pm (revision 91f110e0) 
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 = '1.28';
190our $DEBUG;
191our $VERBOSE;
192our $PRETTY;
193our $TRACEONLY = 0;
194our $WARNTRACE = 0;
195
196use Config;
197my $privlib = $Config{privlibexp};
198if ($^O eq 'VMS') {
199    require VMS::Filespec;
200    $privlib = VMS::Filespec::unixify($privlib);
201}
202my @trypod = (
203	   "$privlib/pod/perldiag.pod",
204	   "$privlib/pods/perldiag.pod",
205	  );
206# handy for development testing of new warnings etc
207unshift @trypod, "./pod/perldiag.pod" if -e "pod/perldiag.pod";
208(my $PODFILE) = ((grep { -e } @trypod), $trypod[$#trypod])[0];
209
210$DEBUG ||= 0;
211my $WHOAMI = ref bless [];  # nobody's business, prolly not even mine
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 $file ( (map { "$_/$WHOAMI.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 $0";
260}
261
262
263%HTML_2_Troff = (
264    'amp'	=>	'&',	#   ampersand
265    'lt'	=>	'<',	#   left chevron, less-than
266    'gt'	=>	'>',	#   right chevron, greater-than
267    'quot'	=>	'"',	#   double quote
268
269    "Aacute"	=>	"A\\*'",	#   capital A, acute accent
270    # etc
271
272);
273
274%HTML_2_Latin_1 = (
275    'amp'	=>	'&',	#   ampersand
276    'lt'	=>	'<',	#   left chevron, less-than
277    'gt'	=>	'>',	#   right chevron, greater-than
278    'quot'	=>	'"',	#   double quote
279
280    "Aacute"	=>	"\xC1"	#   capital A, acute accent
281
282    # etc
283);
284
285%HTML_2_ASCII_7 = (
286    'amp'	=>	'&',	#   ampersand
287    'lt'	=>	'<',	#   left chevron, less-than
288    'gt'	=>	'>',	#   right chevron, greater-than
289    'quot'	=>	'"',	#   double quote
290
291    "Aacute"	=>	"A"	#   capital A, acute accent
292    # etc
293);
294
295our %HTML_Escapes;
296*HTML_Escapes = do {
297    if ($standalone) {
298	$PRETTY ? \%HTML_2_Latin_1 : \%HTML_2_ASCII_7;
299    } else {
300	\%HTML_2_Latin_1;
301    }
302};
303
304*THITHER = $standalone ? *STDOUT : *STDERR;
305
306my %transfmt = ();
307my $transmo = <<EOFUNC;
308sub transmo {
309    #local \$^W = 0;  # recursive warnings we do NOT need!
310EOFUNC
311
312my %msg;
313{
314    print STDERR "FINISHING COMPILATION for $_\n" if $DEBUG;
315    local $/ = '';
316    local $_;
317    my $header;
318    my @headers;
319    my $for_item;
320    my $seen_body;
321    while (<POD_DIAG>) {
322
323	sub _split_pod_link {
324	    $_[0] =~ '(?:([^|]*)\|)?([^/]*)(?:/("?)(.*)\3)?';
325	    ($1,$2,$4);
326	}
327
328	unescape();
329	if ($PRETTY) {
330	    sub noop   { return $_[0] }  # spensive for a noop
331	    sub bold   { my $str =$_[0];  $str =~ s/(.)/$1\b$1/g; return $str; }
332	    sub italic { my $str = $_[0]; $str =~ s/(.)/_\b$1/g;  return $str; }
333	    s/C<<< (.*?) >>>|C<< (.*?) >>|[BC]<(.*?)>/bold($+)/ges;
334	    s/[IF]<(.*?)>/italic($1)/ges;
335	    s/L<(.*?)>/
336	       my($text,$page,$sect) = _split_pod_link($1);
337	       defined $text
338	        ? $text
339	        : defined $sect
340	           ? italic($sect) . ' in ' . italic($page)
341	           : italic($page)
342	     /ges;
343	     s/S<(.*?)>/
344               $1
345             /ges;
346	} else {
347	    s/C<<< (.*?) >>>|C<< (.*?) >>|[BC]<(.*?)>/$+/gs;
348	    s/[IF]<(.*?)>/$1/gs;
349	    s/L<(.*?)>/
350	       my($text,$page,$sect) = _split_pod_link($1);
351	       defined $text
352	        ? $text
353	        : defined $sect
354	           ? qq '"$sect" in $page'
355	           : $page
356	     /ges;
357	    s/S<(.*?)>/
358               $1
359             /ges;
360	}
361	unless (/^=/) {
362	    if (defined $header) {
363		if ( $header eq 'DESCRIPTION' &&
364		    (   /Optional warnings are enabled/
365		     || /Some of these messages are generic./
366		    ) )
367		{
368		    next;
369		}
370		s/^/    /gm;
371		$msg{$header} .= $_;
372		for my $h(@headers) { $msg{$h} .= $_ }
373		++$seen_body;
374	 	undef $for_item;
375	    }
376	    next;
377	}
378
379	# If we have not come across the body of the description yet, then
380	# the previous header needs to share the same description.
381	if ($seen_body) {
382	    @headers = ();
383	}
384	else {
385	    push @headers, $header if defined $header;
386	}
387
388	unless ( s/=item (.*?)\s*\z//) {
389
390	    if ( s/=head1\sDESCRIPTION//) {
391		$msg{$header = 'DESCRIPTION'} = '';
392		undef $for_item;
393	    }
394	    elsif( s/^=for\s+diagnostics\s*\n(.*?)\s*\z// ) {
395		$for_item = $1;
396	    }
397	    next;
398	}
399
400	if( $for_item ) { $header = $for_item; undef $for_item }
401	else {
402	    $header = $1;
403	    while( $header =~ /[;,]\z/ ) {
404		<POD_DIAG> =~ /^\s*(.*?)\s*\z/;
405		$header .= ' '.$1;
406	    }
407	}
408
409	# strip formatting directives from =item line
410	$header =~ s/[A-Z]<(.*?)>/$1/g;
411
412	# Since we strip "\.\n" when we search a warning, strip it here as well
413	$header =~ s/\.?$//;
414
415        my @toks = split( /(%l?[dxX]|%u|%c|%(?:\.\d+)?[fs])/, $header );
416	if (@toks > 1) {
417            my $conlen = 0;
418            for my $i (0..$#toks){
419                if( $i % 2 ){
420                    if(      $toks[$i] eq '%c' ){
421                        $toks[$i] = '.';
422                    } elsif( $toks[$i] =~ /^%(?:d|u)$/ ){
423                        $toks[$i] = '\d+';
424                    } elsif( $toks[$i] =~ '^%(?:s|.*f)$' ){
425                        $toks[$i] = $i == $#toks ? '.*' : '.*?';
426                    } elsif( $toks[$i] =~ '%.(\d+)s' ){
427                        $toks[$i] = ".{$1}";
428                    } elsif( $toks[$i] =~ '^%l*([xX])$' ){
429                        $toks[$i] = $1 eq 'x' ? '[\da-f]+' : '[\dA-F]+';
430                    }
431                } elsif( length( $toks[$i] ) ){
432                    $toks[$i] = quotemeta $toks[$i];
433                    $conlen += length( $toks[$i] );
434                }
435            }
436            my $lhs = join( '', @toks );
437	    $transfmt{$header}{pat} =
438              "    s{^$lhs}\n     {\Q$header\E}s\n\t&& return 1;\n";
439            $transfmt{$header}{len} = $conlen;
440	} else {
441            $transfmt{$header}{pat} =
442	      "    m{^\Q$header\E} && return 1;\n";
443            $transfmt{$header}{len} = length( $header );
444	}
445
446	print STDERR "$WHOAMI: Duplicate entry: \"$header\"\n"
447	    if $msg{$header};
448
449	$msg{$header} = '';
450	$seen_body = 0;
451    }
452
453
454    close POD_DIAG unless *main::DATA eq *POD_DIAG;
455
456    die "No diagnostics?" unless %msg;
457
458    # Apply patterns in order of decreasing sum of lengths of fixed parts
459    # Seems the best way of hitting the right one.
460    for my $hdr ( sort { $transfmt{$b}{len} <=> $transfmt{$a}{len} }
461                  keys %transfmt ){
462        $transmo .= $transfmt{$hdr}{pat};
463    }
464    $transmo .= "    return 0;\n}\n";
465    print STDERR $transmo if $DEBUG;
466    eval $transmo;
467    die $@ if $@;
468}
469
470if ($standalone) {
471    if (!@ARGV and -t STDIN) { print STDERR "$0: Reading from STDIN\n" }
472    while (defined (my $error = <>)) {
473	splainthis($error) || print THITHER $error;
474    }
475    exit;
476}
477
478my $olddie;
479my $oldwarn;
480
481sub import {
482    shift;
483    $^W = 1; # yup, clobbered the global variable;
484	     # tough, if you want diags, you want diags.
485    return if defined $SIG{__WARN__} && ($SIG{__WARN__} eq \&warn_trap);
486
487    for (@_) {
488
489	/^-d(ebug)?$/ 	   	&& do {
490				    $DEBUG++;
491				    next;
492				   };
493
494	/^-v(erbose)?$/ 	&& do {
495				    $VERBOSE++;
496				    next;
497				   };
498
499	/^-p(retty)?$/ 		&& do {
500				    print STDERR "$0: I'm afraid it's too late for prettiness.\n";
501				    $PRETTY++;
502				    next;
503			       };
504	# matches trace and traceonly for legacy doc mixup reasons
505	/^-t(race(only)?)?$/	&& do {
506				    $TRACEONLY++;
507				    next;
508			       };
509	/^-w(arntrace)?$/ 	&& do {
510				    $WARNTRACE++;
511				    next;
512			       };
513
514	warn "Unknown flag: $_";
515    }
516
517    $oldwarn = $SIG{__WARN__};
518    $olddie = $SIG{__DIE__};
519    $SIG{__WARN__} = \&warn_trap;
520    $SIG{__DIE__} = \&death_trap;
521}
522
523sub enable { &import }
524
525sub disable {
526    shift;
527    return unless $SIG{__WARN__} eq \&warn_trap;
528    $SIG{__WARN__} = $oldwarn || '';
529    $SIG{__DIE__} = $olddie || '';
530}
531
532sub warn_trap {
533    my $warning = $_[0];
534    if (caller eq $WHOAMI or !splainthis($warning)) {
535	if ($WARNTRACE) {
536	    print STDERR Carp::longmess($warning);
537	} else {
538	    print STDERR $warning;
539	}
540    }
541    goto &$oldwarn if defined $oldwarn and $oldwarn and $oldwarn ne \&warn_trap;
542};
543
544sub death_trap {
545    my $exception = $_[0];
546
547    # See if we are coming from anywhere within an eval. If so we don't
548    # want to explain the exception because it's going to get caught.
549    my $in_eval = 0;
550    my $i = 0;
551    while (my $caller = (caller($i++))[3]) {
552      if ($caller eq '(eval)') {
553	$in_eval = 1;
554	last;
555      }
556    }
557
558    splainthis($exception) unless $in_eval;
559    if (caller eq $WHOAMI) { print STDERR "INTERNAL EXCEPTION: $exception"; }
560    &$olddie if defined $olddie and $olddie and $olddie ne \&death_trap;
561
562    return if $in_eval;
563
564    # We don't want to unset these if we're coming from an eval because
565    # then we've turned off diagnostics.
566
567    # Switch off our die/warn handlers so we don't wind up in our own
568    # traps.
569    $SIG{__DIE__} = $SIG{__WARN__} = '';
570
571    $exception =~ s/\n(?=.)/\n\t/gas;
572
573    die Carp::longmess("__diagnostics__")
574	  =~ s/^__diagnostics__.*?line \d+\.?\n/
575		  "Uncaught exception from user code:\n\t$exception"
576	      /re;
577	# up we go; where we stop, nobody knows, but i think we die now
578	# but i'm deeply afraid of the &$olddie guy reraising and us getting
579	# into an indirect recursion loop
580};
581
582my %exact_duplicate;
583my %old_diag;
584my $count;
585my $wantspace;
586sub splainthis {
587  return 0 if $TRACEONLY;
588  for (my $tmp = shift) {
589    local $\;
590    local $!;
591    ### &finish_compilation unless %msg;
592    s/\.?\n+$//;
593    my $orig = $_;
594    # return unless defined;
595
596    # get rid of the where-are-we-in-input part
597    s/, <.*?> (?:line|chunk).*$//;
598
599    # Discard 1st " at <file> line <no>" and all text beyond
600    # but be aware of messages containing " at this-or-that"
601    my $real = 0;
602    my @secs = split( / at / );
603    return unless @secs;
604    $_ = $secs[0];
605    for my $i ( 1..$#secs ){
606        if( $secs[$i] =~ /.+? (?:line|chunk) \d+/ ){
607            $real = 1;
608            last;
609        } else {
610            $_ .= ' at ' . $secs[$i];
611	}
612    }
613
614    # remove parenthesis occurring at the end of some messages
615    s/^\((.*)\)$/$1/;
616
617    if ($exact_duplicate{$orig}++) {
618	return &transmo;
619    } else {
620	return 0 unless &transmo;
621    }
622
623    my $short = shorten($orig);
624    if ($old_diag{$_}) {
625	autodescribe();
626	print THITHER "$short (#$old_diag{$_})\n";
627	$wantspace = 1;
628    } elsif (!$msg{$_} && $orig =~ /\n./s) {
629	# A multiline message, like "Attempt to reload /
630	# Compilation failed"
631	my $found;
632	for (split /^/, $orig) {
633	    splainthis($_) and $found = 1;
634	}
635	return $found;
636    } else {
637	autodescribe();
638	$old_diag{$_} = ++$count;
639	print THITHER "\n" if $wantspace;
640	$wantspace = 0;
641	print THITHER "$short (#$old_diag{$_})\n";
642	if ($msg{$_}) {
643	    print THITHER $msg{$_};
644	} else {
645	    if (0 and $standalone) {
646		print THITHER "    **** Error #$old_diag{$_} ",
647			($real ? "is" : "appears to be"),
648			" an unknown diagnostic message.\n\n";
649	    }
650	    return 0;
651	}
652    }
653    return 1;
654  }
655}
656
657sub autodescribe {
658    if ($VERBOSE and not $count) {
659	print THITHER &{$PRETTY ? \&bold : \&noop}("DESCRIPTION OF DIAGNOSTICS"),
660		"\n$msg{DESCRIPTION}\n";
661    }
662}
663
664sub unescape {
665    s {
666            E<
667            ( [A-Za-z]+ )
668            >
669    } {
670         do {
671             exists $HTML_Escapes{$1}
672                ? do { $HTML_Escapes{$1} }
673                : do {
674                    warn "Unknown escape: E<$1> in $_";
675                    "E<$1>";
676                }
677         }
678    }egx;
679}
680
681sub shorten {
682    my $line = $_[0];
683    if (length($line) > 79 and index($line, "\n") == -1) {
684	my $space_place = rindex($line, ' ', 79);
685	if ($space_place != -1) {
686	    substr($line, $space_place, 1) = "\n\t";
687	}
688    }
689    return $line;
690}
691
692
6931 unless $standalone;  # or it'll complain about itself
694__END__ # wish diag dbase were more accessible
695