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 { $diagnostics::PRETTY = 1 }
157 I could start up faster by delaying compilation until it should be
158 needed, but this gets a "panic: top_level" when using the pragma form
161 While it's true that this documentation is somewhat subserious, if you use
162 a program named I<splain>, you should expect a bit of whimsy.
166 Tom Christiansen <F<tchrist@mox.perl.com>>, 25 June 1995.
176 ($privlib, $archlib) = @Config{qw(privlibexp archlibexp)};
178 require VMS::Filespec;
179 $privlib = VMS::Filespec::unixify($privlib);
180 $archlib = VMS::Filespec::unixify($archlib);
183 "$archlib/pod/perldiag.pod",
184 "$privlib/pod/perldiag-$].pod",
185 "$privlib/pod/perldiag.pod",
186 "$archlib/pods/perldiag.pod",
187 "$privlib/pods/perldiag-$].pod",
188 "$privlib/pods/perldiag.pod",
190 # handy for development testing of new warnings etc
191 unshift @trypod, "./pod/perldiag.pod" if -e "pod/perldiag.pod";
192 ($PODFILE) = ((grep { -e } @trypod), $trypod[$#trypod])[0];
195 my $WHOAMI = ref bless []; # nobody's business, prolly not even mine
202 $opt_p = $opt_d = $opt_v = $opt_f = '';
203 %HTML_2_Troff = %HTML_2_Latin_1 = %HTML_2_ASCII_7 = ();
204 %exact_duplicate = ();
209 Getopt::Std::getopts('pdvf:')
210 or die "Usage: $0 [-v] [-p] [-f splainpod]";
211 $PODFILE = $opt_f if $opt_f;
212 $DEBUG = 2 if $opt_d;
217 if (open(POD_DIAG, $PODFILE)) {
218 warn "Happy happy podfile from real $PODFILE\n" if $DEBUG;
224 for $file ( (map { "$_/$WHOAMI.pm" } @INC), $0) {
225 warn "Checking $file\n" if $DEBUG;
226 if (open(POD_DIAG, $file)) {
228 next unless /^__END__\s*# wish diag dbase were more accessible/;
229 print STDERR "podfile is $file\n" if $DEBUG;
236 print STDERR "podfile is <DATA>\n" if $DEBUG;
237 *POD_DIAG = *main::DATA;
241 die "couldn't find diagnostic data in $PODFILE @INC $0";
246 'amp' => '&', # ampersand
247 'lt' => '<', # left chevron, less-than
248 'gt' => '>', # right chevron, greater-than
249 'quot' => '"', # double quote
251 "Aacute" => "A\\*'", # capital A, acute accent
257 'amp' => '&', # ampersand
258 'lt' => '<', # left chevron, less-than
259 'gt' => '>', # right chevron, greater-than
260 'quot' => '"', # double quote
262 "Aacute" => "\xC1" # capital A, acute accent
268 'amp' => '&', # ampersand
269 'lt' => '<', # left chevron, less-than
270 'gt' => '>', # right chevron, greater-than
271 'quot' => '"', # double quote
273 "Aacute" => "A" # capital A, acute accent
279 $PRETTY ? \%HTML_2_Latin_1 : \%HTML_2_ASCII_7;
285 *THITHER = $standalone ? *STDOUT : *STDERR;
289 #local \$^W = 0; # recursive warnings we do NOT need!
293 ### sub finish_compilation { # 5.001e panic: top_level for embedded version
294 print STDERR "FINISHING COMPILATION for $_\n" if $DEBUG;
304 sub noop { return $_[0] } # spensive for a noop
305 sub bold { my $str =$_[0]; $str =~ s/(.)/$1\b$1/g; return $str; }
306 sub italic { my $str = $_[0]; $str =~ s/(.)/_\b$1/g; return $str; }
307 s/[BC]<(.*?)>/bold($1)/ges;
308 s/[LIF]<(.*?)>/italic($1)/ges;
311 s/[LIF]<(.*?)>/$1/gs;
314 if (defined $header) {
315 if ( $header eq 'DESCRIPTION' &&
316 ( /Optional warnings are enabled/
317 || /Some of these messages are generic./
327 unless ( s/=item (.*)\s*\Z//) {
329 if ( s/=head1\sDESCRIPTION//) {
330 $msg{$header = 'DESCRIPTION'} = '';
335 # strip formatting directives in =item line
336 ($header = $1) =~ s/[A-Z]<(.*?)>/$1/g;
338 if ($header =~ /%[csd]/) {
339 $rhs = $lhs = $header;
340 #if ($lhs =~ s/(.*?)%d(?!%d)(.*)/\Q$1\E\\d+\Q$2\E\$/g) {
341 if ($lhs =~ s/(.*?)%d(?!%d)(.*)/\Q$1\E\\d+\Q$2\E/g) {
342 $lhs =~ s/\\%s/.*?/g;
344 # if i had lookbehind negations, i wouldn't have to do this \377 noise
345 $lhs =~ s/(.*?)%s/\Q$1\E.*?\377/g;
346 #$lhs =~ s/\377([^\377]*)$/\Q$1\E\$/;
347 $lhs =~ s/\377([^\377]*)$/\Q$1\E/;
349 $lhs =~ s/\.\*\?$/.*/; # Allow %s at the end to eat it all
352 $transmo .= " s{^$lhs}\n {\Q$rhs\E}s\n\t&& return 1;\n";
354 $transmo .= " m{^\Q$header\E} && return 1;\n";
357 print STDERR "$WHOAMI: Duplicate entry: \"$header\"\n"
364 close POD_DIAG unless *main::DATA eq *POD_DIAG;
366 die "No diagnostics?" unless %msg;
368 $transmo .= " return 0;\n}\n";
369 print STDERR $transmo if $DEBUG;
376 if (!@ARGV and -t STDIN) { print STDERR "$0: Reading from STDIN\n" }
377 while (defined ($error = <>)) {
378 splainthis($error) || print THITHER $error;
383 $oldwarn = ''; $olddie = '';
389 $^W = 1; # yup, clobbered the global variable; tough, if you
390 # want diags, you want diags.
391 return if $SIG{__WARN__} eq \&warn_trap;
395 /^-d(ebug)?$/ && do {
400 /^-v(erbose)?$/ && do {
405 /^-p(retty)?$/ && do {
406 print STDERR "$0: I'm afraid it's too late for prettiness.\n";
411 warn "Unknown flag: $_";
414 $oldwarn = $SIG{__WARN__};
415 $olddie = $SIG{__DIE__};
416 $SIG{__WARN__} = \&warn_trap;
417 $SIG{__DIE__} = \&death_trap;
420 sub enable { &import }
425 return unless $SIG{__WARN__} eq \&warn_trap;
426 $SIG{__WARN__} = $oldwarn;
427 $SIG{__DIE__} = $olddie;
432 if (caller eq $WHOAMI or !splainthis($warning)) {
433 print STDERR $warning;
435 &$oldwarn if defined $oldwarn and $oldwarn and $oldwarn ne \&warn_trap;
439 my $exception = $_[0];
441 # See if we are coming from anywhere within an eval. If so we don't
442 # want to explain the exception because it's going to get caught.
446 my $caller = (caller($i++))[3] or last;
447 if ($caller eq '(eval)') {
453 splainthis($exception) unless $in_eval;
454 if (caller eq $WHOAMI) { print STDERR "INTERNAL EXCEPTION: $exception"; }
455 &$olddie if defined $olddie and $olddie and $olddie ne \&death_trap;
457 # We don't want to unset these if we're coming from an eval because
458 # then we've turned off diagnostics. (Actually what does this next
460 $SIG{__DIE__} = $SIG{__WARN__} = '' unless $in_eval;
461 local($Carp::CarpLevel) = 1;
462 confess "Uncaught exception from user code:\n\t$exception";
463 # up we go; where we stop, nobody knows, but i think we die now
464 # but i'm deeply afraid of the &$olddie guy reraising and us getting
465 # into an indirect recursion loop
471 ### &finish_compilation unless %msg;
474 # return unless defined;
475 s/, <.*?> (?:line|chunk).*$//;
476 $real = s/(.*?) at .*? (?:line|chunk) \d+.*/$1/;
478 if ($exact_duplicate{$orig}++) {
482 return 0 unless &transmo;
484 $orig = shorten($orig);
487 print THITHER "$orig (#$old_diag{$_})\n";
491 $old_diag{$_} = ++$count;
492 print THITHER "\n" if $wantspace;
494 print THITHER "$orig (#$old_diag{$_})\n";
496 print THITHER $msg{$_};
498 if (0 and $standalone) {
499 print THITHER " **** Error #$old_diag{$_} ",
500 ($real ? "is" : "appears to be"),
501 " an unknown diagnostic message.\n\n";
510 if ($VERBOSE and not $count) {
511 print THITHER &{$PRETTY ? \&bold : \&noop}("DESCRIPTION OF DIAGNOSTICS"),
512 "\n$msg{DESCRIPTION}\n";
523 exists $HTML_Escapes{$1}
524 ? do { $HTML_Escapes{$1} }
526 warn "Unknown escape: E<$1> in $_";
535 if (length($line) > 79 and index($line, "\n") == -1) {
536 my $space_place = rindex($line, ' ', 79);
537 if ($space_place != -1) {
538 substr($line, $space_place, 1) = "\n\t";
545 # have to do this: RS isn't set until run time, but we're executing at compiletime
548 1 unless $standalone; # or it'll complain about itself
549 __END__ # wish diag dbase were more accessible