5 diagnostics - Perl compiler pragma to force verbose warning diagnostics
7 splain - standalone program to do the same thing
14 use diagnostics -verbose;
21 perl program 2>diag.out
22 splain [-v] [-p] diag.out
27 =head2 The C<diagnostics> Pragma
29 This module extends the terse diagnostics normally emitted by both the
30 perl compiler and the perl interpreter, augmenting them with the more
31 explicative and endearing descriptions found in L<perldiag>. Like the
32 other pragmata, it affects the compilation phase of your program rather
33 than merely the execution phase.
35 To use in your program as a pragma, merely invoke
39 at the start (or near the start) of your program. (Note
40 that this I<does> enable perl's B<-w> flag.) Your whole
41 compilation will then be subject(ed :-) to the enhanced diagnostics.
42 These still go out B<STDERR>.
44 Due to the interaction between runtime and compiletime issues,
45 and because it's probably not a very good idea anyway,
46 you may not use C<no diagnostics> to turn them off at compiletime.
47 However, you may control there behaviour at runtime using the
48 disable() and enable() methods to turn them off and on respectively.
50 The B<-verbose> flag first prints out the L<perldiag> introduction before
51 any other diagnostics. The $diagnostics::PRETTY variable can generate nicer
52 escape sequences for pagers.
54 Warnings dispatched from perl itself (or more accurately, those that match
55 descriptions found in L<perldiag>) are only displayed once (no duplicate
56 descriptions). User code generated warnings ala warn() are unaffected,
57 allowing duplicate user messages to be displayed.
59 =head2 The I<splain> Program
61 While apparently a whole nuther program, I<splain> is actually nothing
62 more than a link to the (executable) F<diagnostics.pm> module, as well as
63 a link to the F<diagnostics.pod> documentation. The B<-v> flag is like
64 the C<use diagnostics -verbose> directive.
65 The B<-p> flag is like the
66 $diagnostics::PRETTY variable. Since you're post-processing with
67 I<splain>, there's no sense in being able to enable() or disable() processing.
69 Output from I<splain> is directed to B<STDOUT>, unlike the pragma.
73 The following file is certain to trigger a few errors at both
74 runtime and compiletime:
77 print NOWHERE "nothing\n";
78 print STDERR "\n\tThis message should be unadorned.\n";
79 warn "\tThis is a user warning";
80 print "\nDIAGNOSTIC TESTER: Please enter a <CR> here: ";
81 my $a, $b = scalar <STDIN>;
85 If you prefer to run your program first and look at its problem
88 perl -w test.pl 2>test.out
91 Note that this is not in general possible in shells of more dubious heritage,
94 (perl -w test.pl >/dev/tty) >& test.out
97 Because you just moved the existing B<stdout> to somewhere else.
99 If you don't want to modify your source code, but still have on-the-fly
102 exec 3>&1; perl -w test.pl 2>&1 1>&3 3>&- | splain 1>&2 3>&-
106 If you want to control warnings on the fly, do something like this.
107 Make sure you do the C<use> first, or you won't be able to get
108 at the enable() or disable() methods.
110 use diagnostics; # checks entire compilation phase
111 print "\ntime for 1st bogus diags: SQUAWKINGS\n";
113 print "done with 1st bogus\n";
115 disable diagnostics; # only turns off runtime warnings
116 print "\ntime for 2nd bogus: (squelched)\n";
118 print "done with 2nd bogus\n";
120 enable diagnostics; # turns back on runtime warnings
121 print "\ntime for 3rd bogus: SQUAWKINGS\n";
123 print "done with 3rd bogus\n";
126 print "\ntime for 4th bogus: (squelched)\n";
128 print "done with 4th bogus\n";
132 Diagnostic messages derive from the F<perldiag.pod> file when available at
133 runtime. Otherwise, they may be embedded in the file itself when the
134 splain package is built. See the F<Makefile> for details.
136 If an extant $SIG{__WARN__} handler is discovered, it will continue
137 to be honored, but only after the diagnostics::splainthis() function
138 (the module's $SIG{__WARN__} interceptor) has had its way with your
141 There is a $diagnostics::DEBUG variable you may set if you're desperately
142 curious what sorts of things are being intercepted.
144 BEGIN { $diagnostics::DEBUG = 1 }
149 Not being able to say "no diagnostics" is annoying, but may not be
152 The C<-pretty> directive is called too late to affect matters.
153 You have to do this instead, and I<before> you load the module.
155 BEGIN { $diagnostics::PRETTY = 1 }
157 I could start up faster by delaying compilation until it should be
158 needed, but this gets a "panic: top_level" when using the pragma form
161 While it's true that this documentation is somewhat subserious, if you use
162 a program named I<splain>, you should expect a bit of whimsy.
166 Tom Christiansen <F<tchrist@mox.perl.com>>, 25 June 1995.
174 ($privlib, $archlib) = @Config{qw(privlibexp archlibexp)};
176 require VMS::Filespec;
177 $privlib = VMS::Filespec::unixify($privlib);
178 $archlib = VMS::Filespec::unixify($archlib);
180 @trypod = ("$archlib/pod/perldiag.pod",
181 "$privlib/pod/perldiag-$].pod",
182 "$privlib/pod/perldiag.pod");
183 # handy for development testing of new warnings etc
184 unshift @trypod, "./pod/perldiag.pod" if -e "pod/perldiag.pod";
185 ($PODFILE) = ((grep { -e } @trypod), $trypod[$#trypod])[0];
188 my $WHOAMI = ref bless []; # nobody's business, prolly not even mine
195 $opt_p = $opt_d = $opt_v = $opt_f = '';
196 %HTML_2_Troff = %HTML_2_Latin_1 = %HTML_2_ASCII_7 = ();
197 %exact_duplicate = ();
202 Getopt::Std::getopts('pdvf:')
203 or die "Usage: $0 [-v] [-p] [-f splainpod]";
204 $PODFILE = $opt_f if $opt_f;
205 $DEBUG = 2 if $opt_d;
210 if (open(POD_DIAG, $PODFILE)) {
211 warn "Happy happy podfile from real $PODFILE\n" if $DEBUG;
217 for $file ( (map { "$_/$WHOAMI.pm" } @INC), $0) {
218 warn "Checking $file\n" if $DEBUG;
219 if (open(POD_DIAG, $file)) {
221 next unless /^__END__\s*# wish diag dbase were more accessible/;
222 print STDERR "podfile is $file\n" if $DEBUG;
229 print STDERR "podfile is <DATA>\n" if $DEBUG;
230 *POD_DIAG = *main::DATA;
234 die "couldn't find diagnostic data in $PODFILE @INC $0";
239 'amp' => '&', # ampersand
240 'lt' => '<', # left chevron, less-than
241 'gt' => '>', # right chevron, greater-than
242 'quot' => '"', # double quote
244 "Aacute" => "A\\*'", # capital A, acute accent
250 'amp' => '&', # ampersand
251 'lt' => '<', # left chevron, less-than
252 'gt' => '>', # right chevron, greater-than
253 'quot' => '"', # double quote
255 "Aacute" => "\xC1" # capital A, acute accent
261 'amp' => '&', # ampersand
262 'lt' => '<', # left chevron, less-than
263 'gt' => '>', # right chevron, greater-than
264 'quot' => '"', # double quote
266 "Aacute" => "A" # capital A, acute accent
272 $PRETTY ? \%HTML_2_Latin_1 : \%HTML_2_ASCII_7;
278 *THITHER = $standalone ? *STDOUT : *STDERR;
282 #local \$^W = 0; # recursive warnings we do NOT need!
286 ### sub finish_compilation { # 5.001e panic: top_level for embedded version
287 print STDERR "FINISHING COMPILATION for $_\n" if $DEBUG;
297 sub noop { return $_[0] } # spensive for a noop
298 sub bold { my $str =$_[0]; $str =~ s/(.)/$1\b$1/g; return $str; }
299 sub italic { my $str = $_[0]; $str =~ s/(.)/_\b$1/g; return $str; }
300 s/[BC]<(.*?)>/bold($1)/ges;
301 s/[LIF]<(.*?)>/italic($1)/ges;
304 s/[LIF]<(.*?)>/$1/gs;
307 if (defined $header) {
308 if ( $header eq 'DESCRIPTION' &&
309 ( /Optional warnings are enabled/
310 || /Some of these messages are generic./
320 unless ( s/=item (.*)\s*\Z//) {
322 if ( s/=head1\sDESCRIPTION//) {
323 $msg{$header = 'DESCRIPTION'} = '';
328 # strip formatting directives in =item line
329 ($header = $1) =~ s/[A-Z]<(.*?)>/$1/g;
331 if ($header =~ /%[sd]/) {
332 $rhs = $lhs = $header;
333 #if ($lhs =~ s/(.*?)%d(?!%d)(.*)/\Q$1\E\\d+\Q$2\E\$/g) {
334 if ($lhs =~ s/(.*?)%d(?!%d)(.*)/\Q$1\E\\d+\Q$2\E/g) {
335 $lhs =~ s/\\%s/.*?/g;
337 # if i had lookbehind negations, i wouldn't have to do this \377 noise
338 $lhs =~ s/(.*?)%s/\Q$1\E.*?\377/g;
339 #$lhs =~ s/\377([^\377]*)$/\Q$1\E\$/;
340 $lhs =~ s/\377([^\377]*)$/\Q$1\E/;
342 $lhs =~ s/\.\*\?$/.*/; # Allow %s at the end to eat it all
344 $transmo .= " s{^$lhs}\n {\Q$rhs\E}s\n\t&& return 1;\n";
346 $transmo .= " m{^\Q$header\E} && return 1;\n";
349 print STDERR "$WHOAMI: Duplicate entry: \"$header\"\n"
356 close POD_DIAG unless *main::DATA eq *POD_DIAG;
358 die "No diagnostics?" unless %msg;
360 $transmo .= " return 0;\n}\n";
361 print STDERR $transmo if $DEBUG;
368 if (!@ARGV and -t STDIN) { print STDERR "$0: Reading from STDIN\n" }
369 while (defined ($error = <>)) {
370 splainthis($error) || print THITHER $error;
374 $old_w = 0; $oldwarn = ''; $olddie = '';
380 $^W = 1; # yup, clobbered the global variable; tough, if you
381 # want diags, you want diags.
382 return if $SIG{__WARN__} eq \&warn_trap;
386 /^-d(ebug)?$/ && do {
391 /^-v(erbose)?$/ && do {
396 /^-p(retty)?$/ && do {
397 print STDERR "$0: I'm afraid it's too late for prettiness.\n";
402 warn "Unknown flag: $_";
405 $oldwarn = $SIG{__WARN__};
406 $olddie = $SIG{__DIE__};
407 $SIG{__WARN__} = \&warn_trap;
408 $SIG{__DIE__} = \&death_trap;
411 sub enable { &import }
416 return unless $SIG{__WARN__} eq \&warn_trap;
417 $SIG{__WARN__} = $oldwarn;
418 $SIG{__DIE__} = $olddie;
423 if (caller eq $WHOAMI or !splainthis($warning)) {
424 print STDERR $warning;
426 &$oldwarn if defined $oldwarn and $oldwarn and $oldwarn ne \&warn_trap;
430 my $exception = $_[0];
432 # See if we are coming from anywhere within an eval. If so we don't
433 # want to explain the exception because it's going to get caught.
437 my $caller = (caller($i++))[3] or last;
438 if ($caller eq '(eval)') {
444 splainthis($exception) unless $in_eval;
445 if (caller eq $WHOAMI) { print STDERR "INTERNAL EXCEPTION: $exception"; }
446 &$olddie if defined $olddie and $olddie and $olddie ne \&death_trap;
448 # We don't want to unset these if we're coming from an eval because
449 # then we've turned off diagnostics. (Actually what does this next
451 $SIG{__DIE__} = $SIG{__WARN__} = '' unless $in_eval;
452 local($Carp::CarpLevel) = 1;
453 confess "Uncaught exception from user code:\n\t$exception";
454 # up we go; where we stop, nobody knows, but i think we die now
455 # but i'm deeply afraid of the &$olddie guy reraising and us getting
456 # into an indirect recursion loop
462 ### &finish_compilation unless %msg;
465 # return unless defined;
466 s/, <.*?> (?:line|chunk).*$//;
467 $real = s/(.*?) at .*? (?:line|chunk) \d+.*/$1/;
469 if ($exact_duplicate{$orig}++) {
473 return 0 unless &transmo;
475 $orig = shorten($orig);
478 print THITHER "$orig (#$old_diag{$_})\n";
482 $old_diag{$_} = ++$count;
483 print THITHER "\n" if $wantspace;
485 print THITHER "$orig (#$old_diag{$_})\n";
487 print THITHER $msg{$_};
489 if (0 and $standalone) {
490 print THITHER " **** Error #$old_diag{$_} ",
491 ($real ? "is" : "appears to be"),
492 " an unknown diagnostic message.\n\n";
501 if ($VERBOSE and not $count) {
502 print THITHER &{$PRETTY ? \&bold : \&noop}("DESCRIPTION OF DIAGNOSTICS"),
503 "\n$msg{DESCRIPTION}\n";
514 exists $HTML_Escapes{$1}
515 ? do { $HTML_Escapes{$1} }
517 warn "Unknown escape: E<$1> in $_";
526 if (length($line) > 79 and index($line, "\n") == -1) {
527 my $space_place = rindex($line, ' ', 79);
528 if ($space_place != -1) {
529 substr($line, $space_place, 1) = "\n\t";
536 # have to do this: RS isn't set until run time, but we're executing at compiletime
539 1 unless $standalone; # or it'll complain about itself
540 __END__ # wish diag dbase were more accessible