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 interpeter, 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 =head2 The I<splain> Program
56 While apparently a whole nuther program, I<splain> is actually nothing
57 more than a link to the (executable) F<diagnostics.pm> module, as well as
58 a link to the F<diagnostics.pod> documentation. The B<-v> flag is like
59 the C<use diagnostics -verbose> directive.
60 The B<-p> flag is like the
61 $diagnostics::PRETTY variable. Since you're post-processing with
62 I<splain>, there's no sense in being able to enable() or disable() processing.
64 Output from I<splain> is directed to B<STDOUT>, unlike the pragma.
68 The following file is certain to trigger a few errors at both
69 runtime and compiletime:
72 print NOWHERE "nothing\n";
73 print STDERR "\n\tThis message should be unadorned.\n";
74 warn "\tThis is a user warning";
75 print "\nDIAGNOSTIC TESTER: Please enter a <CR> here: ";
76 my $a, $b = scalar <STDIN>;
80 If you prefer to run your program first and look at its problem
83 perl -w test.pl 2>test.out
86 Note that this is not in general possible in shells of more dubious heritage,
89 (perl -w test.pl >/dev/tty) >& test.out
92 Because you just moved the existing B<stdout> to somewhere else.
94 If you don't want to modify your source code, but still have on-the-fly
97 exec 3>&1; perl -w test.pl 2>&1 1>&3 3>&- | splain 1>&2 3>&-
101 If you want to control warnings on the fly, do something like this.
102 Make sure you do the C<use> first, or you won't be able to get
103 at the enable() or disable() methods.
105 use diagnostics; # checks entire compilation phase
106 print "\ntime for 1st bogus diags: SQUAWKINGS\n";
108 print "done with 1st bogus\n";
110 disable diagnostics; # only turns off runtime warnings
111 print "\ntime for 2nd bogus: (squelched)\n";
113 print "done with 2nd bogus\n";
115 enable diagnostics; # turns back on runtime warnings
116 print "\ntime for 3rd bogus: SQUAWKINGS\n";
118 print "done with 3rd bogus\n";
121 print "\ntime for 4th bogus: (squelched)\n";
123 print "done with 4th bogus\n";
127 Diagnostic messages derive from the F<perldiag.pod> file when available at
128 runtime. Otherwise, they may be embedded in the file itself when the
129 splain package is built. See the F<Makefile> for details.
131 If an extant $SIG{__WARN__} handler is discovered, it will continue
132 to be honored, but only after the diagnostics::splainthis() function
133 (the module's $SIG{__WARN__} interceptor) has had its way with your
136 There is a $diagnostics::DEBUG variable you may set if you're desperately
137 curious what sorts of things are being intercepted.
139 BEGIN { $diagnostics::DEBUG = 1 }
144 Not being able to say "no diagnostics" is annoying, but may not be
147 The C<-pretty> directive is called too late to affect matters.
148 You have to do this instead, and I<before> you load the module.
150 BEGIN { $diagnostics::PRETTY = 1 }
152 I could start up faster by delaying compilation until it should be
153 needed, but this gets a "panic: top_level" when using the pragma form
156 While it's true that this documentation is somewhat subserious, if you use
157 a program named I<splain>, you should expect a bit of whimsy.
161 Tom Christiansen <F<tchrist@mox.perl.com>>, 25 June 1995.
169 ($privlib, $archlib) = @Config{qw(privlibexp archlibexp)};
171 require VMS::Filespec;
172 $privlib = VMS::Filespec::unixify($privlib);
173 $archlib = VMS::Filespec::unixify($archlib);
175 @trypod = ("$archlib/pod/perldiag.pod",
176 "$privlib/pod/perldiag-$].pod",
177 "$privlib/pod/perldiag.pod");
178 ($PODFILE) = ((grep { -e } @trypod), $trypod[$#trypod])[0];
181 my $WHOAMI = ref bless []; # nobody's business, prolly not even mine
188 $opt_p = $opt_d = $opt_v = $opt_f = '';
189 %HTML_2_Troff = %HTML_2_Latin_1 = %HTML_2_ASCII_7 = ();
190 %exact_duplicate = ();
195 Getopt::Std::getopts('pdvf:')
196 or die "Usage: $0 [-v] [-p] [-f splainpod]";
197 $PODFILE = $opt_f if $opt_f;
198 $DEBUG = 2 if $opt_d;
203 if (open(POD_DIAG, $PODFILE)) {
204 warn "Happy happy podfile from real $PODFILE\n" if $DEBUG;
210 for $file ( (map { "$_/$WHOAMI.pm" } @INC), $0) {
211 warn "Checking $file\n" if $DEBUG;
212 if (open(POD_DIAG, $file)) {
214 next unless /^__END__\s*# wish diag dbase were more accessible/;
215 print STDERR "podfile is $file\n" if $DEBUG;
222 print STDERR "podfile is <DATA>\n" if $DEBUG;
223 *POD_DIAG = *main::DATA;
227 die "couldn't find diagnostic data in $PODFILE @INC $0";
232 'amp' => '&', # ampersand
233 'lt' => '<', # left chevron, less-than
234 'gt' => '>', # right chevron, greater-than
235 'quot' => '"', # double quote
237 "Aacute" => "A\\*'", # capital A, acute accent
243 'amp' => '&', # ampersand
244 'lt' => '<', # left chevron, less-than
245 'gt' => '>', # right chevron, greater-than
246 'quot' => '"', # double quote
248 "Aacute" => "\xC1" # capital A, acute accent
254 'amp' => '&', # ampersand
255 'lt' => '<', # left chevron, less-than
256 'gt' => '>', # right chevron, greater-than
257 'quot' => '"', # double quote
259 "Aacute" => "A" # capital A, acute accent
265 $PRETTY ? \%HTML_2_Latin_1 : \%HTML_2_ASCII_7;
271 *THITHER = $standalone ? *STDOUT : *STDERR;
275 local \$^W = 0; # recursive warnings we do NOT need!
279 ### sub finish_compilation { # 5.001e panic: top_level for embedded version
280 print STDERR "FINISHING COMPILATION for $_\n" if $DEBUG;
290 sub noop { return $_[0] } # spensive for a noop
291 sub bold { my $str =$_[0]; $str =~ s/(.)/$1\b$1/g; return $str; }
292 sub italic { my $str = $_[0]; $str =~ s/(.)/_\b$1/g; return $str; }
293 s/[BC]<(.*?)>/bold($1)/ges;
294 s/[LIF]<(.*?)>/italic($1)/ges;
297 s/[LIF]<(.*?)>/$1/gs;
300 if (defined $header) {
301 if ( $header eq 'DESCRIPTION' &&
302 ( /Optional warnings are enabled/
303 || /Some of these messages are generic./
313 unless ( s/=item (.*)\s*\Z//) {
315 if ( s/=head1\sDESCRIPTION//) {
316 $msg{$header = 'DESCRIPTION'} = '';
321 # strip formatting directives in =item line
322 ($header = $1) =~ s/[A-Z]<(.*?)>/$1/g;
324 if ($header =~ /%[sd]/) {
325 $rhs = $lhs = $header;
326 #if ($lhs =~ s/(.*?)%d(?!%d)(.*)/\Q$1\E\\d+\Q$2\E\$/g) {
327 if ($lhs =~ s/(.*?)%d(?!%d)(.*)/\Q$1\E\\d+\Q$2\E/g) {
328 $lhs =~ s/\\%s/.*?/g;
330 # if i had lookbehind negations, i wouldn't have to do this \377 noise
331 $lhs =~ s/(.*?)%s/\Q$1\E.*?\377/g;
332 #$lhs =~ s/\377([^\377]*)$/\Q$1\E\$/;
333 $lhs =~ s/\377([^\377]*)$/\Q$1\E/;
335 $lhs =~ s/\.\*\?$/.*/; # Allow %s at the end to eat it all
337 $transmo .= " s{^$lhs}\n {\Q$rhs\E}s\n\t&& return 1;\n";
339 $transmo .= " m{^\Q$header\E} && return 1;\n";
342 print STDERR "$WHOAMI: Duplicate entry: \"$header\"\n"
349 close POD_DIAG unless *main::DATA eq *POD_DIAG;
351 die "No diagnostics?" unless %msg;
353 $transmo .= " return 0;\n}\n";
354 print STDERR $transmo if $DEBUG;
361 if (!@ARGV and -t STDIN) { print STDERR "$0: Reading from STDIN\n" }
362 while (defined ($error = <>)) {
363 splainthis($error) || print THITHER $error;
367 $old_w = 0; $oldwarn = ''; $olddie = '';
373 $^W = 1; # yup, clobbered the global variable; tough, if you
374 # want diags, you want diags.
375 return if $SIG{__WARN__} eq \&warn_trap;
379 /^-d(ebug)?$/ && do {
384 /^-v(erbose)?$/ && do {
389 /^-p(retty)?$/ && do {
390 print STDERR "$0: I'm afraid it's too late for prettiness.\n";
395 warn "Unknown flag: $_";
398 $oldwarn = $SIG{__WARN__};
399 $olddie = $SIG{__DIE__};
400 $SIG{__WARN__} = \&warn_trap;
401 $SIG{__DIE__} = \&death_trap;
404 sub enable { &import }
409 return unless $SIG{__WARN__} eq \&warn_trap;
410 $SIG{__WARN__} = $oldwarn;
411 $SIG{__DIE__} = $olddie;
416 if (caller eq $WHOAMI or !splainthis($warning)) {
417 print STDERR $warning;
419 &$oldwarn if defined $oldwarn and $oldwarn and $oldwarn ne \&warn_trap;
423 my $exception = $_[0];
425 # See if we are coming from anywhere within an eval. If so we don't
426 # want to explain the exception because it's going to get caught.
430 my $caller = (caller($i++))[3] or last;
431 if ($caller eq '(eval)') {
437 splainthis($exception) unless $in_eval;
438 if (caller eq $WHOAMI) { print STDERR "INTERNAL EXCEPTION: $exception"; }
439 &$olddie if defined $olddie and $olddie and $olddie ne \&death_trap;
441 # We don't want to unset these if we're coming from an eval because
442 # then we've turned off diagnostics. (Actually what does this next
444 $SIG{__DIE__} = $SIG{__WARN__} = '' unless $in_eval;
445 local($Carp::CarpLevel) = 1;
446 confess "Uncaught exception from user code:\n\t$exception";
447 # up we go; where we stop, nobody knows, but i think we die now
448 # but i'm deeply afraid of the &$olddie guy reraising and us getting
449 # into an indirect recursion loop
455 ### &finish_compilation unless %msg;
458 # return unless defined;
459 if ($exact_duplicate{$_}++) {
462 s/, <.*?> (?:line|chunk).*$//;
463 $real = s/(.*?) at .*? (?:line|chunk) \d+.*/$1/;
465 return 0 unless &transmo;
466 $orig = shorten($orig);
469 print THITHER "$orig (#$old_diag{$_})\n";
473 $old_diag{$_} = ++$count;
474 print THITHER "\n" if $wantspace;
476 print THITHER "$orig (#$old_diag{$_})\n";
478 print THITHER $msg{$_};
480 if (0 and $standalone) {
481 print THITHER " **** Error #$old_diag{$_} ",
482 ($real ? "is" : "appears to be"),
483 " an unknown diagnostic message.\n\n";
492 if ($VERBOSE and not $count) {
493 print THITHER &{$PRETTY ? \&bold : \&noop}("DESCRIPTION OF DIAGNOSTICS"),
494 "\n$msg{DESCRIPTION}\n";
505 exists $HTML_Escapes{$1}
506 ? do { $HTML_Escapes{$1} }
508 warn "Unknown escape: E<$1> in $_";
517 if (length($line) > 79 and index($line, "\n") == -1) {
518 my $space_place = rindex($line, ' ', 79);
519 if ($space_place != -1) {
520 substr($line, $space_place, 1) = "\n\t";
527 # have to do this: RS isn't set until run time, but we're executing at compile time
530 1 unless $standalone; # or it'll complain about itself
531 __END__ # wish diag dbase were more accessible