package Filter::cpp; use Filter::Util::Exec ; use Config ; use strict; use warnings; our $VERSION = '1.60' ; my $cpp; my $sep; if ($^O eq 'MSWin32') { $cpp = 'cpp.exe' ; $sep = ';'; } else { ($cpp) = $Config{cppstdin} =~ /^(\S+)/; $sep = ':'; } if (! $cpp) { require Carp; Carp::croak ("Cannot find cpp\n"); } # Check if cpp is installed if ( ! -x $cpp) { my $foundCPP = 0 ; foreach my $dir (split($sep, $ENV{PATH}), '') { if (-x "$dir/$cpp") { $foundCPP = 1; last ; } } if (! $foundCPP) { require Carp; Carp::croak("Cannot find cpp\n"); } } sub import { my($self, @args) = @_ ; if ($^O eq 'MSWin32') { Filter::Util::Exec::filter_add ($self, 'cmd', '/c', "cpp.exe 2>nul") ; } else { Filter::Util::Exec::filter_add ($self, 'sh', '-c', "$Config{'cppstdin'} $Config{'cppminus'} 2>/dev/null") ; } } 1 ; __END__ =head1 NAME Filter::cpp - cpp source filter =head1 SYNOPSIS use Filter::cpp ; =head1 DESCRIPTION This source filter pipes the current source file through the C pre-processor (cpp) if it is available. As with all source filters its scope is limited to the current source file only. Every file you want to be processed by the filter must have a use Filter::cpp ; near the top. Here is an example script which uses the filter: use Filter::cpp ; #define FRED 1 $a = 2 + FRED ; print "a = $a\n" ; #ifdef FRED print "Hello FRED\n" ; #else print "Where is FRED\n" ; #endif And here is what it will output: a = 3 Hello FRED This example below, provided by Michael G Schwern, shows a clever way to get Perl to use a C pre-processor macro when the Filter::cpp module is available, or to use a Perl sub when it is not. # use Filter::cpp if we can. BEGIN { eval 'use Filter::cpp' } sub PRINT { my($string) = shift; #define PRINT($string) \ (print $string."\n") } PRINT("Mu"); Look at Michael's Tie::VecArray module for a practical use. =head1 AUTHOR Paul Marquess =head1 DATE 11th December 1995. =cut