1package O; 2 3our $VERSION = '1.01'; 4 5use B qw(minus_c save_BEGINs); 6use Carp; 7 8sub import { 9 my ($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<O::import> function loads the appropriate C<B::Backend> module 111and calls its C<compile> function, passing it OPTIONS. That function 112is expected to return a sub reference which we'll call CALLBACK. Next, 113the "compile-only" flag is switched on (equivalent to the command-line 114option C<-c>) and a CHECK block is registered which calls 115CALLBACK. Thus the main Perl program mentioned on the command-line is 116read in, parsed and compiled into internal syntax tree form. Since the 117C<-c> flag is set, the program does not start running (excepting BEGIN 118blocks of course) but the CALLBACK function registered by the compiler 119backend is called. 120 121In summary, a compiler backend module should be called "B::Foo" 122for some foo and live in the appropriate directory for that name. 123It should define a function called C<compile>. When the user types 124 125 perl -MO=Foo,OPTIONS foo.pl 126 127that function is called and is passed those OPTIONS (split on 128commas). It should return a sub ref to the main compilation function. 129After the user's program is loaded and parsed, that returned sub ref 130is invoked which can then go ahead and do the compilation, usually by 131making use of the C<B> module's functionality. 132 133=head1 BUGS 134 135The C<-q> and C<-qq> options don't work correctly if perl isn't 136compiled with PerlIO support : STDOUT will be closed instead of being 137redirected to C<$O::BEGIN_output>. 138 139=head1 AUTHOR 140 141Malcolm Beattie, C<mbeattie@sable.ox.ac.uk> 142 143=cut 144