1package O; 2 3our $VERSION = '1.00'; 4 5use B qw(minus_c save_BEGINs); 6use Carp; 7 8sub import { 9 my ($class, @options) = @_; 10 my ($quiet, $veryquiet) = (0, 0); 11 if ($options[0] eq '-q' || $options[0] eq '-qq') { 12 $quiet = 1; 13 open (SAVEOUT, ">&STDOUT"); 14 close STDOUT; 15 open (STDOUT, ">", \$O::BEGIN_output); 16 if ($options[0] eq '-qq') { 17 $veryquiet = 1; 18 } 19 shift @options; 20 } 21 my $backend = shift (@options); 22 eval q[ 23 BEGIN { 24 minus_c; 25 save_BEGINs; 26 } 27 28 CHECK { 29 if ($quiet) { 30 close STDOUT; 31 open (STDOUT, ">&SAVEOUT"); 32 close SAVEOUT; 33 } 34 35 # Note: if you change the code after this 'use', please 36 # change the fudge factors in B::Concise (grep for 37 # "fragile kludge") so that its output still looks 38 # nice. Thanks. --smcc 39 use B::].$backend.q[ (); 40 if ($@) { 41 croak "use of backend $backend failed: $@"; 42 } 43 44 45 my $compilesub = &{"B::${backend}::compile"}(@options); 46 if (ref($compilesub) ne "CODE") { 47 die $compilesub; 48 } 49 50 local $savebackslash = $\; 51 local ($\,$",$,) = (undef,' ',''); 52 &$compilesub(); 53 54 close STDERR if $veryquiet; 55 } 56 ]; 57 die $@ if $@; 58} 59 601; 61 62__END__ 63 64=head1 NAME 65 66O - Generic interface to Perl Compiler backends 67 68=head1 SYNOPSIS 69 70 perl -MO=[-q,]Backend[,OPTIONS] foo.pl 71 72=head1 DESCRIPTION 73 74This is the module that is used as a frontend to the Perl Compiler. 75 76If you pass the C<-q> option to the module, then the STDOUT 77filehandle will be redirected into the variable C<$O::BEGIN_output> 78during compilation. This has the effect that any output printed 79to STDOUT by BEGIN blocks or use'd modules will be stored in this 80variable rather than printed. It's useful with those backends which 81produce output themselves (C<Deparse>, C<Concise> etc), so that 82their output is not confused with that generated by the code 83being compiled. 84 85The C<-qq> option behaves like C<-q>, except that it also closes 86STDERR after deparsing has finished. This suppresses the "Syntax OK" 87message normally produced by perl. 88 89=head1 CONVENTIONS 90 91Most compiler backends use the following conventions: OPTIONS 92consists of a comma-separated list of words (no white-space). 93The C<-v> option usually puts the backend into verbose mode. 94The C<-ofile> option generates output to B<file> instead of 95stdout. The C<-D> option followed by various letters turns on 96various internal debugging flags. See the documentation for the 97desired backend (named C<B::Backend> for the example above) to 98find out about that backend. 99 100=head1 IMPLEMENTATION 101 102This section is only necessary for those who want to write a 103compiler backend module that can be used via this module. 104 105The command-line mentioned in the SYNOPSIS section corresponds to 106the Perl code 107 108 use O ("Backend", OPTIONS); 109 110The C<import> function which that calls loads in the appropriate 111C<B::Backend> module and calls the C<compile> function in that 112package, passing it OPTIONS. That function is expected to return 113a sub reference which we'll call CALLBACK. Next, the "compile-only" 114flag is switched on (equivalent to the command-line option C<-c>) 115and a CHECK block is registered which calls CALLBACK. Thus the main 116Perl program mentioned on the command-line is read in, parsed and 117compiled into internal syntax tree form. Since the C<-c> flag is 118set, the program does not start running (excepting BEGIN blocks of 119course) but the CALLBACK function registered by the compiler 120backend is called. 121 122In summary, a compiler backend module should be called "B::Foo" 123for some foo and live in the appropriate directory for that name. 124It should define a function called C<compile>. When the user types 125 126 perl -MO=Foo,OPTIONS foo.pl 127 128that function is called and is passed those OPTIONS (split on 129commas). It should return a sub ref to the main compilation function. 130After the user's program is loaded and parsed, that returned sub ref 131is invoked which can then go ahead and do the compilation, usually by 132making use of the C<B> module's functionality. 133 134=head1 BUGS 135 136The C<-q> and C<-qq> options don't work correctly if perl isn't 137compiled with PerlIO support : STDOUT will be closed instead of being 138redirected to C<$O::BEGIN_output>. 139 140=head1 AUTHOR 141 142Malcolm Beattie, C<mbeattie@sable.ox.ac.uk> 143 144=cut 145