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pragma: use diagnostics; use diagnostics -verbose; enable diagnostics; disable diagnostics; Using the C standalone filter program: perl program 2>diag.out splain [-v] [-p] diag.out Using diagnostics to get stack traces from a misbehaving script: perl -Mdiagnostics=-traceonly my_script.pl =head1 DESCRIPTION =head2 The C Pragma This module extends the terse diagnostics normally emitted by both the perl compiler and the perl interpreter (from running perl with a -w switch or C), augmenting them with the more explicative and endearing descriptions found in L. Like the other pragmata, it affects the compilation phase of your program rather than merely the execution phase. To use in your program as a pragma, merely invoke use diagnostics; at the start (or near the start) of your program. (Note that this I enable perl's B<-w> flag.) Your whole compilation will then be subject(ed :-) to the enhanced diagnostics. These still go out B. Due to the interaction between runtime and compiletime issues, and because it's probably not a very good idea anyway, you may not use C to turn them off at compiletime. However, you may control their behaviour at runtime using the disable() and enable() methods to turn them off and on respectively. The B<-verbose> flag first prints out the L introduction before any other diagnostics. The $diagnostics::PRETTY variable can generate nicer escape sequences for pagers. Warnings dispatched from perl itself (or more accurately, those that match descriptions found in L) are only displayed once (no duplicate descriptions). User code generated warnings a la warn() are unaffected, allowing duplicate user messages to be displayed. This module also adds a stack trace to the error message when perl dies. This is useful for pinpointing what caused the death. The B<-traceonly> (or just B<-t>) flag turns off the explanations of warning messages leaving just the stack traces. So if your script is dieing, run it again with perl -Mdiagnostics=-traceonly my_bad_script to see the call stack at the time of death. By supplying the B<-warntrace> (or just B<-w>) flag, any warnings emitted will also come with a stack trace. =head2 The I Program While apparently a whole nuther program, I is actually nothing more than a link to the (executable) F module, as well as a link to the F documentation. The B<-v> flag is like the C directive. The B<-p> flag is like the $diagnostics::PRETTY variable. Since you're post-processing with I, there's no sense in being able to enable() or disable() processing. Output from I is directed to B, unlike the pragma. =head1 EXAMPLES The following file is certain to trigger a few errors at both runtime and compiletime: use diagnostics; print NOWHERE "nothing\n"; print STDERR "\n\tThis message should be unadorned.\n"; warn "\tThis is a user warning"; print "\nDIAGNOSTIC TESTER: Please enter a here: "; my $a, $b = scalar ; print "\n"; print $x/$y; If you prefer to run your program first and look at its problem afterwards, do this: perl -w test.pl 2>test.out ./splain < test.out Note that this is not in general possible in shells of more dubious heritage, as the theoretical (perl -w test.pl >/dev/tty) >& test.out ./splain < test.out Because you just moved the existing B to somewhere else. If you don't want to modify your source code, but still have on-the-fly warnings, do this: exec 3>&1; perl -w test.pl 2>&1 1>&3 3>&- | splain 1>&2 3>&- Nifty, eh? If you want to control warnings on the fly, do something like this. Make sure you do the C first, or you won't be able to get at the enable() or disable() methods. use diagnostics; # checks entire compilation phase print "\ntime for 1st bogus diags: SQUAWKINGS\n"; print BOGUS1 'nada'; print "done with 1st bogus\n"; disable diagnostics; # only turns off runtime warnings print "\ntime for 2nd bogus: (squelched)\n"; print BOGUS2 'nada'; print "done with 2nd bogus\n"; enable diagnostics; # turns back on runtime warnings print "\ntime for 3rd bogus: SQUAWKINGS\n"; print BOGUS3 'nada'; print "done with 3rd bogus\n"; disable diagnostics; print "\ntime for 4th bogus: (squelched)\n"; print BOGUS4 'nada'; print "done with 4th bogus\n"; =head1 INTERNALS Diagnostic messages derive from the F file when available at runtime. Otherwise, they may be embedded in the file itself when the splain package is built. See the F for details. If an extant $SIG{__WARN__} handler is discovered, it will continue to be honored, but only after the diagnostics::splainthis() function (the module's $SIG{__WARN__} interceptor) has had its way with your warnings. There is a $diagnostics::DEBUG variable you may set if you're desperately curious what sorts of things are being intercepted. BEGIN { $diagnostics::DEBUG = 1 } =head1 BUGS Not being able to say "no diagnostics" is annoying, but may not be insurmountable. The C<-pretty> directive is called too late to affect matters. You have to do this instead, and I you load the module. BEGIN { $diagnostics::PRETTY = 1 } I could start up faster by delaying compilation until it should be needed, but this gets a "panic: top_level" when using the pragma form in Perl 5.001e. While it's true that this documentation is somewhat subserious, if you use a program named I, you should expect a bit of whimsy. =head1 AUTHOR Tom Christiansen >, 25 June 1995. =cut use strict; use 5.009001; use Carp; $Carp::Internal{__PACKAGE__.""}++; our $VERSION = '1.28'; our $DEBUG; our $VERBOSE; our $PRETTY; our $TRACEONLY = 0; our $WARNTRACE = 0; use Config; my $privlib = $Config{privlibexp}; if ($^O eq 'VMS') { require VMS::Filespec; $privlib = VMS::Filespec::unixify($privlib); } my @trypod = ( "$privlib/pod/perldiag.pod", "$privlib/pods/perldiag.pod", ); # handy for development testing of new warnings etc unshift @trypod, "./pod/perldiag.pod" if -e "pod/perldiag.pod"; (my $PODFILE) = ((grep { -e } @trypod), $trypod[$#trypod])[0]; $DEBUG ||= 0; my $WHOAMI = ref bless []; # nobody's business, prolly not even mine local $| = 1; local $_; local $.; my $standalone; my(%HTML_2_Troff, %HTML_2_Latin_1, %HTML_2_ASCII_7); CONFIG: { our $opt_p = our $opt_d = our $opt_v = our $opt_f = ''; unless (caller) { $standalone++; require Getopt::Std; Getopt::Std::getopts('pdvf:') or die "Usage: $0 [-v] [-p] [-f splainpod]"; $PODFILE = $opt_f if $opt_f; $DEBUG = 2 if $opt_d; $VERBOSE = $opt_v; $PRETTY = $opt_p; } if (open(POD_DIAG, $PODFILE)) { warn "Happy happy podfile from real $PODFILE\n" if $DEBUG; last CONFIG; } if (caller) { INCPATH: { for my $file ( (map { "$_/$WHOAMI.pm" } @INC), $0) { warn "Checking $file\n" if $DEBUG; if (open(POD_DIAG, $file)) { while () { next unless /^__END__\s*# wish diag dbase were more accessible/; print STDERR "podfile is $file\n" if $DEBUG; last INCPATH; } } } } } else { print STDERR "podfile is \n" if $DEBUG; *POD_DIAG = *main::DATA; } } if (eof(POD_DIAG)) { die "couldn't find diagnostic data in $PODFILE @INC $0"; } %HTML_2_Troff = ( 'amp' => '&', # ampersand 'lt' => '<', # left chevron, less-than 'gt' => '>', # right chevron, greater-than 'quot' => '"', # double quote "Aacute" => "A\\*'", # capital A, acute accent # etc ); %HTML_2_Latin_1 = ( 'amp' => '&', # ampersand 'lt' => '<', # left chevron, less-than 'gt' => '>', # right chevron, greater-than 'quot' => '"', # double quote "Aacute" => "\xC1" # capital A, acute accent # etc ); %HTML_2_ASCII_7 = ( 'amp' => '&', # ampersand 'lt' => '<', # left chevron, less-than 'gt' => '>', # right chevron, greater-than 'quot' => '"', # double quote "Aacute" => "A" # capital A, acute accent # etc ); our %HTML_Escapes; *HTML_Escapes = do { if ($standalone) { $PRETTY ? \%HTML_2_Latin_1 : \%HTML_2_ASCII_7; } else { \%HTML_2_Latin_1; } }; *THITHER = $standalone ? *STDOUT : *STDERR; my %transfmt = (); my $transmo = <) { sub _split_pod_link { $_[0] =~ '(?:([^|]*)\|)?([^/]*)(?:/("?)(.*)\3)?'; ($1,$2,$4); } unescape(); if ($PRETTY) { sub noop { return $_[0] } # spensive for a noop sub bold { my $str =$_[0]; $str =~ s/(.)/$1\b$1/g; return $str; } sub italic { my $str = $_[0]; $str =~ s/(.)/_\b$1/g; return $str; } s/C<<< (.*?) >>>|C<< (.*?) >>|[BC]<(.*?)>/bold($+)/ges; s/[IF]<(.*?)>/italic($1)/ges; s/L<(.*?)>/ my($text,$page,$sect) = _split_pod_link($1); defined $text ? $text : defined $sect ? italic($sect) . ' in ' . italic($page) : italic($page) /ges; s/S<(.*?)>/ $1 /ges; } else { s/C<<< (.*?) >>>|C<< (.*?) >>|[BC]<(.*?)>/$+/gs; s/[IF]<(.*?)>/$1/gs; s/L<(.*?)>/ my($text,$page,$sect) = _split_pod_link($1); defined $text ? $text : defined $sect ? qq '"$sect" in $page' : $page /ges; s/S<(.*?)>/ $1 /ges; } unless (/^=/) { if (defined $header) { if ( $header eq 'DESCRIPTION' && ( /Optional warnings are enabled/ || /Some of these messages are generic./ ) ) { next; } s/^/ /gm; $msg{$header} .= $_; for my $h(@headers) { $msg{$h} .= $_ } ++$seen_body; undef $for_item; } next; } # If we have not come across the body of the description yet, then # the previous header needs to share the same description. if ($seen_body) { @headers = (); } else { push @headers, $header if defined $header; } unless ( s/=item (.*?)\s*\z//) { if ( s/=head1\sDESCRIPTION//) { $msg{$header = 'DESCRIPTION'} = ''; undef $for_item; } elsif( s/^=for\s+diagnostics\s*\n(.*?)\s*\z// ) { $for_item = $1; } next; } if( $for_item ) { $header = $for_item; undef $for_item } else { $header = $1; while( $header =~ /[;,]\z/ ) { =~ /^\s*(.*?)\s*\z/; $header .= ' '.$1; } } # strip formatting directives from =item line $header =~ s/[A-Z]<(.*?)>/$1/g; # Since we strip "\.\n" when we search a warning, strip it here as well $header =~ s/\.?$//; my @toks = split( /(%l?[dxX]|%u|%c|%(?:\.\d+)?[fs])/, $header ); if (@toks > 1) { my $conlen = 0; for my $i (0..$#toks){ if( $i % 2 ){ if( $toks[$i] eq '%c' ){ $toks[$i] = '.'; } elsif( $toks[$i] =~ /^%(?:d|u)$/ ){ $toks[$i] = '\d+'; } elsif( $toks[$i] =~ '^%(?:s|.*f)$' ){ $toks[$i] = $i == $#toks ? '.*' : '.*?'; } elsif( $toks[$i] =~ '%.(\d+)s' ){ $toks[$i] = ".{$1}"; } elsif( $toks[$i] =~ '^%l*([xX])$' ){ $toks[$i] = $1 eq 'x' ? '[\da-f]+' : '[\dA-F]+'; } } elsif( length( $toks[$i] ) ){ $toks[$i] = quotemeta $toks[$i]; $conlen += length( $toks[$i] ); } } my $lhs = join( '', @toks ); $transfmt{$header}{pat} = " s{^$lhs}\n {\Q$header\E}s\n\t&& return 1;\n"; $transfmt{$header}{len} = $conlen; } else { $transfmt{$header}{pat} = " m{^\Q$header\E} && return 1;\n"; $transfmt{$header}{len} = length( $header ); } print STDERR "$WHOAMI: Duplicate entry: \"$header\"\n" if $msg{$header}; $msg{$header} = ''; $seen_body = 0; } close POD_DIAG unless *main::DATA eq *POD_DIAG; die "No diagnostics?" unless %msg; # Apply patterns in order of decreasing sum of lengths of fixed parts # Seems the best way of hitting the right one. for my $hdr ( sort { $transfmt{$b}{len} <=> $transfmt{$a}{len} } keys %transfmt ){ $transmo .= $transfmt{$hdr}{pat}; } $transmo .= " return 0;\n}\n"; print STDERR $transmo if $DEBUG; eval $transmo; die $@ if $@; } if ($standalone) { if (!@ARGV and -t STDIN) { print STDERR "$0: Reading from STDIN\n" } while (defined (my $error = <>)) { splainthis($error) || print THITHER $error; } exit; } my $olddie; my $oldwarn; sub import { shift; $^W = 1; # yup, clobbered the global variable; # tough, if you want diags, you want diags. return if defined $SIG{__WARN__} && ($SIG{__WARN__} eq \&warn_trap); for (@_) { /^-d(ebug)?$/ && do { $DEBUG++; next; }; /^-v(erbose)?$/ && do { $VERBOSE++; next; }; /^-p(retty)?$/ && do { print STDERR "$0: I'm afraid it's too late for prettiness.\n"; $PRETTY++; next; }; # matches trace and traceonly for legacy doc mixup reasons /^-t(race(only)?)?$/ && do { $TRACEONLY++; next; }; /^-w(arntrace)?$/ && do { $WARNTRACE++; next; }; warn "Unknown flag: $_"; } $oldwarn = $SIG{__WARN__}; $olddie = $SIG{__DIE__}; $SIG{__WARN__} = \&warn_trap; $SIG{__DIE__} = \&death_trap; } sub enable { &import } sub disable { shift; return unless $SIG{__WARN__} eq \&warn_trap; $SIG{__WARN__} = $oldwarn || ''; $SIG{__DIE__} = $olddie || ''; } sub warn_trap { my $warning = $_[0]; if (caller eq $WHOAMI or !splainthis($warning)) { if ($WARNTRACE) { print STDERR Carp::longmess($warning); } else { print STDERR $warning; } } goto &$oldwarn if defined $oldwarn and $oldwarn and $oldwarn ne \&warn_trap; }; sub death_trap { my $exception = $_[0]; # See if we are coming from anywhere within an eval. If so we don't # want to explain the exception because it's going to get caught. my $in_eval = 0; my $i = 0; while (my $caller = (caller($i++))[3]) { if ($caller eq '(eval)') { $in_eval = 1; last; } } splainthis($exception) unless $in_eval; if (caller eq $WHOAMI) { print STDERR "INTERNAL EXCEPTION: $exception"; } &$olddie if defined $olddie and $olddie and $olddie ne \&death_trap; return if $in_eval; # We don't want to unset these if we're coming from an eval because # then we've turned off diagnostics. # Switch off our die/warn handlers so we don't wind up in our own # traps. $SIG{__DIE__} = $SIG{__WARN__} = ''; $exception =~ s/\n(?=.)/\n\t/gas; die Carp::longmess("__diagnostics__") =~ s/^__diagnostics__.*?line \d+\.?\n/ "Uncaught exception from user code:\n\t$exception" /re; # up we go; where we stop, nobody knows, but i think we die now # but i'm deeply afraid of the &$olddie guy reraising and us getting # into an indirect recursion loop }; my %exact_duplicate; my %old_diag; my $count; my $wantspace; sub splainthis { return 0 if $TRACEONLY; for (my $tmp = shift) { local $\; local $!; ### &finish_compilation unless %msg; s/\.?\n+$//; my $orig = $_; # return unless defined; # get rid of the where-are-we-in-input part s/, <.*?> (?:line|chunk).*$//; # Discard 1st " at line " and all text beyond # but be aware of messages containing " at this-or-that" my $real = 0; my @secs = split( / at / ); return unless @secs; $_ = $secs[0]; for my $i ( 1..$#secs ){ if( $secs[$i] =~ /.+? (?:line|chunk) \d+/ ){ $real = 1; last; } else { $_ .= ' at ' . $secs[$i]; } } # remove parenthesis occurring at the end of some messages s/^$(.*)$$/$1/; if ($exact_duplicate{$orig}++) { return &transmo; } else { return 0 unless &transmo; } my $short = shorten($orig); if ($old_diag{$_}) { autodescribe(); print THITHER "$short (#$old_diag{$_})\n"; $wantspace = 1; } elsif (!$msg{$_} && $orig =~ /\n./s) { # A multiline message, like "Attempt to reload / # Compilation failed" my $found; for (split /^/, $orig) { splainthis($_) and $found = 1; } return $found; } else { autodescribe(); $old_diag{$_} = ++$count; print THITHER "\n" if $wantspace; $wantspace = 0; print THITHER "$short (#$old_diag{$_})\n"; if ($msg{$_}) { print THITHER $msg{$_}; } else { if (0 and $standalone) { print THITHER " **** Error #$old_diag{$_} ", ($real ? "is" : "appears to be"), " an unknown diagnostic message.\n\n"; } return 0; } } return 1; } } sub autodescribe { if ($VERBOSE and not $count) { print THITHER &{$PRETTY ? \&bold : \&noop}("DESCRIPTION OF DIAGNOSTICS"), "\n$msg{DESCRIPTION}\n"; } } sub unescape { s { E< ( [A-Za-z]+ ) > } { do { exists $HTML_Escapes{$1} ? do { $HTML_Escapes{$1} } : do { warn "Unknown escape: E<$1> in $_"; "E<$1>"; } } }egx; } sub shorten { my $line = $_[0]; if (length($line) > 79 and index($line, "\n") == -1) { my $space_place = rindex($line, ' ', 79); if ($space_place != -1) { substr($line, $space_place, 1) = "\n\t"; } } return $line; } 1 unless $standalone; # or it'll complain about itself __END__ # wish diag dbase were more accessible