5 diagnostics, splain - produce verbose warning diagnostics
9 Using the C<diagnostics> pragma:
12 use diagnostics -verbose;
17 Using the C<splain> standalone filter program:
19 perl program 2>diag.out
20 splain [-v] [-p] diag.out
22 Using diagnostics to get stack traces from a misbehaving script:
24 perl -Mdiagnostics=-traceonly my_script.pl
28 =head2 The C<diagnostics> Pragma
30 This module extends the terse diagnostics normally emitted by both the
31 perl compiler and the perl interpreter (from running perl with a -w
32 switch or C<use warnings>), augmenting them with the more
33 explicative and endearing descriptions found in L<perldiag>. Like the
34 other pragmata, it affects the compilation phase of your program rather
35 than merely the execution phase.
37 To use in your program as a pragma, merely invoke
41 at the start (or near the start) of your program. (Note
42 that this I<does> enable perl's B<-w> flag.) Your whole
43 compilation will then be subject(ed :-) to the enhanced diagnostics.
44 These still go out B<STDERR>.
46 Due to the interaction between runtime and compiletime issues,
47 and because it's probably not a very good idea anyway,
48 you may not use C<no diagnostics> to turn them off at compiletime.
49 However, you may control their behaviour at runtime using the
50 disable() and enable() methods to turn them off and on respectively.
52 The B<-verbose> flag first prints out the L<perldiag> introduction before
53 any other diagnostics. The $diagnostics::PRETTY variable can generate nicer
54 escape sequences for pagers.
56 Warnings dispatched from perl itself (or more accurately, those that match
57 descriptions found in L<perldiag>) are only displayed once (no duplicate
58 descriptions). User code generated warnings a la warn() are unaffected,
59 allowing duplicate user messages to be displayed.
61 This module also adds a stack trace to the error message when perl dies.
62 This is useful for pinpointing what
63 caused the death. The B<-traceonly> (or
64 just B<-t>) flag turns off the explanations of warning messages leaving just
65 the stack traces. So if your script is dieing, run it again with
67 perl -Mdiagnostics=-traceonly my_bad_script
69 to 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
73 =head2 The I<splain> Program
75 While apparently a whole nuther program, I<splain> is actually nothing
76 more than a link to the (executable) F<diagnostics.pm> module, as well as
77 a link to the F<diagnostics.pod> documentation. The B<-v> flag is like
78 the C<use diagnostics -verbose> directive.
79 The B<-p> flag is like the
80 $diagnostics::PRETTY variable. Since you're post-processing with
81 I<splain>, there's no sense in being able to enable() or disable() processing.
83 Output from I<splain> is directed to B<STDOUT>, unlike the pragma.
87 The following file is certain to trigger a few errors at both
88 runtime and compiletime:
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>;
99 If you prefer to run your program first and look at its problem
102 perl -w test.pl 2>test.out
105 Note that this is not in general possible in shells of more dubious heritage,
108 (perl -w test.pl >/dev/tty) >& test.out
111 Because you just moved the existing B<stdout> to somewhere else.
113 If you don't want to modify your source code, but still have on-the-fly
116 exec 3>&1; perl -w test.pl 2>&1 1>&3 3>&- | splain 1>&2 3>&-
120 If you want to control warnings on the fly, do something like this.
121 Make sure you do the C<use> first, or you won't be able to get
122 at the enable() or disable() methods.
124 use diagnostics; # checks entire compilation phase
125 print "\ntime for 1st bogus diags: SQUAWKINGS\n";
127 print "done with 1st bogus\n";
129 disable diagnostics; # only turns off runtime warnings
130 print "\ntime for 2nd bogus: (squelched)\n";
132 print "done with 2nd bogus\n";
134 enable diagnostics; # turns back on runtime warnings
135 print "\ntime for 3rd bogus: SQUAWKINGS\n";
137 print "done with 3rd bogus\n";
140 print "\ntime for 4th bogus: (squelched)\n";
142 print "done with 4th bogus\n";
146 Diagnostic messages derive from the F<perldiag.pod> file when available at
147 runtime. Otherwise, they may be embedded in the file itself when the
148 splain package is built. See the F<Makefile> for details.
150 If an extant $SIG{__WARN__} handler is discovered, it will continue
151 to be honored, but only after the diagnostics::splainthis() function
152 (the module's $SIG{__WARN__} interceptor) has had its way with your
155 There is a $diagnostics::DEBUG variable you may set if you're desperately
156 curious what sorts of things are being intercepted.
158 BEGIN { $diagnostics::DEBUG = 1 }
163 Not being able to say "no diagnostics" is annoying, but may not be
166 The C<-pretty> directive is called too late to affect matters.
167 You have to do this instead, and I<before> you load the module.
169 BEGIN { $diagnostics::PRETTY = 1 }
171 I could start up faster by delaying compilation until it should be
172 needed, but this gets a "panic: top_level" when using the pragma form
175 While it's true that this documentation is somewhat subserious, if you use
176 a program named I<splain>, you should expect a bit of whimsy.
180 Tom Christiansen <F<tchrist@mox.perl.com>>, 25 June 1995.
187 $Carp::Internal{__PACKAGE__.""}++;
189 our $VERSION = '1.30';
197 my $privlib = $Config{privlibexp};
199 require VMS::Filespec;
200 $privlib = VMS::Filespec::unixify($privlib);
203 "$privlib/pod/perldiag.pod",
204 "$privlib/pods/perldiag.pod",
206 # handy for development testing of new warnings etc
207 unshift @trypod, "./pod/perldiag.pod" if -e "pod/perldiag.pod";
208 (my $PODFILE) = ((grep { -e } @trypod), $trypod[$#trypod])[0];
211 my $WHOAMI = ref bless []; # nobody's business, prolly not even mine
218 my(%HTML_2_Troff, %HTML_2_Latin_1, %HTML_2_ASCII_7);
221 our $opt_p = our $opt_d = our $opt_v = our $opt_f = '';
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;
234 if (open(POD_DIAG, $PODFILE)) {
235 warn "Happy happy podfile from real $PODFILE\n" if $DEBUG;
241 for my $file ( (map { "$_/$WHOAMI.pm" } @INC), $0) {
242 warn "Checking $file\n" if $DEBUG;
243 if (open(POD_DIAG, $file)) {
246 /^__END__\s*# wish diag dbase were more accessible/;
247 print STDERR "podfile is $file\n" if $DEBUG;
254 print STDERR "podfile is <DATA>\n" if $DEBUG;
255 *POD_DIAG = *main::DATA;
259 die "couldn't find diagnostic data in $PODFILE @INC $0";
264 'amp' => '&', # ampersand
265 'lt' => '<', # left chevron, less-than
266 'gt' => '>', # right chevron, greater-than
267 'quot' => '"', # double quote
269 "Aacute" => "A\\*'", # capital A, acute accent
275 'amp' => '&', # ampersand
276 'lt' => '<', # left chevron, less-than
277 'gt' => '>', # right chevron, greater-than
278 'quot' => '"', # double quote
280 "Aacute" => "\xC1" # capital A, acute accent
286 'amp' => '&', # ampersand
287 'lt' => '<', # left chevron, less-than
288 'gt' => '>', # right chevron, greater-than
289 'quot' => '"', # double quote
291 "Aacute" => "A" # capital A, acute accent
298 $PRETTY ? \%HTML_2_Latin_1 : \%HTML_2_ASCII_7;
304 *THITHER = $standalone ? *STDOUT : *STDERR;
307 my $transmo = <<EOFUNC;
309 #local \$^W = 0; # recursive warnings we do NOT need!
314 print STDERR "FINISHING COMPILATION for $_\n" if $DEBUG;
323 sub _split_pod_link {
324 $_[0] =~ '(?:([^|]*)\|)?([^/]*)(?:/("?)(.*)\3)?';
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($1)/ges;
336 my($text,$page,$sect) = _split_pod_link($1);
340 ? italic($sect) . ' in ' . italic($page)
347 s/C<<< (.*?) >>>|C<< (.*?) >>|[BC]<(.*?)>/$+/gs;
350 my($text,$page,$sect) = _split_pod_link($1);
354 ? qq '"$sect" in $page'
362 if (defined $header) {
363 if ( $header eq 'DESCRIPTION' &&
364 ( /Optional warnings are enabled/
365 || /Some of these messages are generic./
372 for my $h(@headers) { $msg{$h} .= $_ }
379 # If we have not come across the body of the description yet, then
380 # the previous header needs to share the same description.
385 push @headers, $header if defined $header;
388 unless ( s/=item (.*?)\s*\z//) {
390 if ( s/=head1\sDESCRIPTION//) {
391 $msg{$header = 'DESCRIPTION'} = '';
394 elsif( s/^=for\s+diagnostics\s*\n(.*?)\s*\z// ) {
400 if( $for_item ) { $header = $for_item; undef $for_item }
403 while( $header =~ /[;,]\z/ ) {
404 <POD_DIAG> =~ /^\s*(.*?)\s*\z/;
409 # strip formatting directives from =item line
410 $header =~ s/[A-Z]<(.*?)>/$1/g;
412 # Since we strip "\.\n" when we search a warning, strip it here as well
415 my @toks = split( /(%l?[dxX]|%[ucp]|%(?:\.\d+)?[fs])/, $header );
418 for my $i (0..$#toks){
420 if( $toks[$i] eq '%c' ){
422 } elsif( $toks[$i] =~ /^%(?:d|u)$/ ){
424 } elsif( $toks[$i] =~ '^%(?:s|.*f)$' ){
425 $toks[$i] = $i == $#toks ? '.*' : '.*?';
426 } elsif( $toks[$i] =~ '%.(\d+)s' ){
428 } elsif( $toks[$i] =~ '^%l*([pxX])$' ){
429 $toks[$i] = $1 eq 'X' ? '[\dA-F]+' : '[\da-f]+';
431 } elsif( length( $toks[$i] ) ){
432 $toks[$i] = quotemeta $toks[$i];
433 $conlen += length( $toks[$i] );
436 my $lhs = join( '', @toks );
437 $transfmt{$header}{pat} =
438 " s
\a^$lhs
\a\Q$header\E
\as\n\t&& return 1;\n";
439 $transfmt{$header}{len} = $conlen;
441 $transfmt{$header}{pat} =
442 " m
\a^\Q$header\E
\a && return 1;\n";
443 $transfmt{$header}{len} = length( $header );
446 print STDERR "$WHOAMI: Duplicate entry: \"$header\"\n"
454 close POD_DIAG unless *main::DATA eq *POD_DIAG;
456 die "No diagnostics?" unless %msg;
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} }
462 $transmo .= $transfmt{$hdr}{pat};
464 $transmo .= " return 0;\n}\n";
465 print STDERR $transmo if $DEBUG;
471 if (!@ARGV and -t STDIN) { print STDERR "$0: Reading from STDIN\n" }
472 while (defined (my $error = <>)) {
473 splainthis($error) || print THITHER $error;
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);
489 /^-d(ebug)?$/ && do {
494 /^-v(erbose)?$/ && do {
499 /^-p(retty)?$/ && do {
500 print STDERR "$0: I'm afraid it's too late for prettiness.\n";
504 # matches trace and traceonly for legacy doc mixup reasons
505 /^-t(race(only)?)?$/ && do {
509 /^-w(arntrace)?$/ && do {
514 warn "Unknown flag: $_";
517 $oldwarn = $SIG{__WARN__};
518 $olddie = $SIG{__DIE__};
519 $SIG{__WARN__} = \&warn_trap;
520 $SIG{__DIE__} = \&death_trap;
523 sub enable { &import }
527 return unless $SIG{__WARN__} eq \&warn_trap;
528 $SIG{__WARN__} = $oldwarn || '';
529 $SIG{__DIE__} = $olddie || '';
534 if (caller eq $WHOAMI or !splainthis($warning)) {
536 print STDERR Carp::longmess($warning);
538 print STDERR $warning;
541 goto &$oldwarn if defined $oldwarn and $oldwarn and $oldwarn ne \&warn_trap;
545 my $exception = $_[0];
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.
551 while (my $caller = (caller($i++))[3]) {
552 if ($caller eq '(eval)') {
558 splainthis($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;
564 # We don't want to unset these if we're coming from an eval because
565 # then we've turned off diagnostics.
567 # Switch off our die/warn handlers so we don't wind up in our own
569 $SIG{__DIE__} = $SIG{__WARN__} = '';
571 $exception =~ s/\n(?=.)/\n\t/gas;
573 die Carp::longmess("__diagnostics__")
574 =~ s/^__diagnostics__.*?line \d+\.?\n/
575 "Uncaught exception from user code:\n\t$exception"
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
587 return 0 if $TRACEONLY;
588 for (my $tmp = shift) {
591 ### &finish_compilation unless %msg;
594 # return unless defined;
596 # get rid of the where-are-we-in-input part
597 s/, <.*?> (?:line|chunk).*$//;
599 # Discard 1st " at <file> line <no>" and all text beyond
600 # but be aware of messages containing " at this-or-that"
602 my @secs = split( / at / );
605 for my $i ( 1..$#secs ){
606 if( $secs[$i] =~ /.+? (?:line|chunk) \d+/ ){
610 $_ .= ' at ' . $secs[$i];
614 # remove parenthesis occurring at the end of some messages
617 if ($exact_duplicate{$orig}++) {
620 return 0 unless &transmo;
623 my $short = shorten($orig);
626 print THITHER "$short (#$old_diag{$_})\n";
628 } elsif (!$msg{$_} && $orig =~ /\n./s) {
629 # A multiline message, like "Attempt to reload /
630 # Compilation failed"
632 for (split /^/, $orig) {
633 splainthis($_) and $found = 1;
638 $old_diag{$_} = ++$count;
639 print THITHER "\n" if $wantspace;
641 print THITHER "$short (#$old_diag{$_})\n";
643 print THITHER $msg{$_};
645 if (0 and $standalone) {
646 print THITHER " **** Error #$old_diag{$_} ",
647 ($real ? "is" : "appears to be"),
648 " an unknown diagnostic message.\n\n";
658 if ($VERBOSE and not $count) {
659 print THITHER &{$PRETTY ? \&bold : \&noop}("DESCRIPTION OF DIAGNOSTICS"),
660 "\n$msg{DESCRIPTION}\n";
671 exists $HTML_Escapes{$1}
672 ? do { $HTML_Escapes{$1} }
674 warn "Unknown escape: E<$1> in $_";
683 if (length($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";
693 1 unless $standalone; # or it'll complain about itself
694 __END__ # wish diag dbase were more accessible