package re; our $VERSION = 0.06_03; =head1 NAME re - Perl pragma to alter regular expression behaviour =head1 SYNOPSIS use re 'taint'; ($x) = ($^X =~ /^(.*)$/s); # $x is tainted here $pat = '(?{ $foo = 1 })'; use re 'eval'; /foo${pat}bar/; # won't fail (when not under -T switch) { no re 'taint'; # the default ($x) = ($^X =~ /^(.*)$/s); # $x is not tainted here no re 'eval'; # the default /foo${pat}bar/; # disallowed (with or without -T switch) } use re 'debug'; # output debugging info during /^(.*)$/s; # compile and run time use re 'debugcolor'; # same as 'debug', but with colored output ... use re qw(Debug All); # Finer tuned debugging options. use re qw(Debug More); no re qw(Debug ALL); # Turn of all re debugging in this scope (We use $^X in these examples because it's tainted by default.) =head1 DESCRIPTION When C is in effect, and a tainted string is the target of a regex, the regex memories (or values returned by the m// operator in list context) are tainted. This feature is useful when regex operations on tainted data aren't meant to extract safe substrings, but to perform other transformations. When C is in effect, a regex is allowed to contain C<(?{ ... })> zero-width assertions even if regular expression contains variable interpolation. That is normally disallowed, since it is a potential security risk. Note that this pragma is ignored when the regular expression is obtained from tainted data, i.e. evaluation is always disallowed with tainted regular expressions. See L. For the purpose of this pragma, interpolation of precompiled regular expressions (i.e., the result of C) is I considered variable interpolation. Thus: /foo${pat}bar/ I allowed if $pat is a precompiled regular expression, even if $pat contains C<(?{ ... })> assertions. When C is in effect, perl emits debugging messages when compiling and using regular expressions. The output is the same as that obtained by running a C<-DDEBUGGING>-enabled perl interpreter with the B<-Dr> switch. It may be quite voluminous depending on the complexity of the match. Using C instead of C enables a form of output that can be used to get a colorful display on terminals that understand termcap color sequences. Set C<$ENV{PERL_RE_TC}> to a comma-separated list of C properties to use for highlighting strings on/off, pre-point part on/off. See L for additional info. Similarly C produces debugging output, the difference being that it allows the fine tuning of what debugging output will be emitted. Options are divided into three groups, those related to compilation, those related to execution and those related to special purposes. The options are as follows: =over 4 =item Compile related options =over 4 =item COMPILE Turns on all compile related debug options. =item PARSE Turns on debug output related to the process of parsing the pattern. =item OPTIMISE Enables output related to the optimisation phase of compilation. =item TRIEC Detailed info about trie compilation. =item DUMP Dump the final program out after it is compiled and optimised. =back =item Execute related options =over 4 =item EXECUTE Turns on all execute related debug options. =item MATCH Turns on debugging of the main matching loop. =item TRIEE Extra debugging of how tries execute. =item INTUIT Enable debugging of start point optimisations. =back =item Extra debugging options =over 4 =item EXTRA Turns on all "extra" debugging options. =item TRIEM Enable enhanced TRIE debugging. Enhances both TRIEE and TRIEC. =item STATE Enable debugging of states in the engine. =item STACK Enable debugging of the recursion stack in the engine. Enabling or disabling this option automatically does the same for debugging states as well. This output from this can be quite large. =item OPTIMISEM Enable enhanced optimisation debugging and start point optimisations. Probably not useful except when debugging the regex engine itself. =item OFFSETS Dump offset information. This can be used to see how regops correlate to the pattern. Output format is NODENUM:POSITION[LENGTH] Where 1 is the position of the first char in the string. Note that position can be 0, or larger than the actual length of the pattern, likewise length can be zero. =item OFFSETSDBG Enable debugging of offsets information. This emits copious amounts of trace information and doesn't mesh well with other debug options. Almost definitely only useful to people hacking on the offsets part of the debug engine. =back =item Other useful flags These are useful shortcuts to save on the typing. =over 4 =item ALL Enable all compile and execute options at once. =item All Enable DUMP and all execute options. Equivalent to: use re 'debug'; =item MORE =item More Enable TRIEM and all execute compile and execute options. =back =back As of 5.9.5 the directive C and its equivalents are lexically scoped, as the other directives are. However they have both compile-time and run-time effects. See L. =cut # N.B. File::Basename contains a literal for 'taint' as a fallback. If # taint is changed here, File::Basename must be updated as well. my %bitmask = ( taint => 0x00100000, # HINT_RE_TAINT eval => 0x00200000, # HINT_RE_EVAL ); sub setcolor { eval { # Ignore errors require Term::Cap; my $terminal = Tgetent Term::Cap ({OSPEED => 9600}); # Avoid warning. my $props = $ENV{PERL_RE_TC} || 'md,me,so,se,us,ue'; my @props = split /,/, $props; my $colors = join "\t", map {$terminal->Tputs($_,1)} @props; $colors =~ s/\0//g; $ENV{PERL_RE_COLORS} = $colors; }; if ($@) { $ENV{PERL_RE_COLORS}||=qq'\t\t> <\t> <\t\t' } } my %flags = ( COMPILE => 0x0000FF, PARSE => 0x000001, OPTIMISE => 0x000002, TRIEC => 0x000004, DUMP => 0x000008, EXECUTE => 0x00FF00, INTUIT => 0x000100, MATCH => 0x000200, TRIEE => 0x000400, EXTRA => 0xFF0000, TRIEM => 0x010000, OFFSETS => 0x020000, OFFSETSDBG => 0x040000, STATE => 0x080000, OPTIMISEM => 0x100000, STACK => 0x280000, ); $flags{ALL} = -1; $flags{All} = $flags{all} = $flags{DUMP} | $flags{EXECUTE}; $flags{Extra} = $flags{EXECUTE} | $flags{COMPILE}; $flags{More} = $flags{MORE} = $flags{All} | $flags{TRIEC} | $flags{TRIEM} | $flags{STATE}; $flags{State} = $flags{DUMP} | $flags{EXECUTE} | $flags{STATE}; $flags{TRIE} = $flags{DUMP} | $flags{EXECUTE} | $flags{TRIEC}; my $installed; my $installed_error; sub _load_unload { my ($on)= @_; if ($on) { if ( ! defined($installed) ) { require XSLoader; $installed = eval { XSLoader::load('re') } || 0; $installed_error = $@; } if ( ! $installed ) { die "'re' not installed!? ($installed_error)"; } else { # We call install() every time, as if we didn't, we wouldn't # "see" any changes to the color environment var since # the last time it was called. # install() returns an integer, which if casted properly # in C resolves to a structure containing the regex # hooks. Setting it to a random integer will guarantee # segfaults. $^H{regcomp} = install(); } } else { delete $^H{regcomp}; } } sub bits { my $on = shift; my $bits = 0; unless (@_) { require Carp; Carp::carp("Useless use of \"re\" pragma"); } foreach my $idx (0..$#_){ my $s=$_[$idx]; if ($s eq 'Debug' or $s eq 'Debugcolor') { setcolor() if $s =~/color/i; ${^RE_DEBUG_FLAGS} = 0 unless defined ${^RE_DEBUG_FLAGS}; for my $idx ($idx+1..$#_) { if ($flags{$_[$idx]}) { if ($on) { ${^RE_DEBUG_FLAGS} |= $flags{$_[$idx]}; } else { ${^RE_DEBUG_FLAGS} &= ~ $flags{$_[$idx]}; } } else { require Carp; Carp::carp("Unknown \"re\" Debug flag '$_[$idx]', possible flags: ", join(", ",sort keys %flags ) ); } } _load_unload($on ? 1 : ${^RE_DEBUG_FLAGS}); last; } elsif ($s eq 'debug' or $s eq 'debugcolor') { setcolor() if $s =~/color/i; _load_unload($on); } elsif (exists $bitmask{$s}) { $bits |= $bitmask{$s}; } else { require Carp; Carp::carp("Unknown \"re\" subpragma '$s' (known ones are: ", join(', ', map {qq('$_')} 'debug', 'debugcolor', sort keys %bitmask), ")"); } } $bits; } sub import { shift; $^H |= bits(1, @_); } sub unimport { shift; $^H &= ~ bits(0, @_); } 1;