lib/perl5/5.6.1/msys/O.pm

   1 package O;
   2 use B qw(minus_c save_BEGINs);
   3 use Carp;
   4
   5 sub import {
   6     my ($class, $backend, @options) = @_;
   7     eval "use B::$backend ()";
   8     if ($@) {
   9         croak "use of backend $backend failed: $@";
  10     }
  11     my $compilesub = &{"B::${backend}::compile"}(@options);
  12     if (ref($compilesub) eq "CODE") {
  13         minus_c;
  14         save_BEGINs;
  15         eval 'CHECK { &$compilesub() }';
  16     } else {
  17         die $compilesub;
  18     }
  19 }
  20
  21 1;
  22
  23 __END__
  24
  25 =head1 NAME
  26
  27 O - Generic interface to Perl Compiler backends
  28
  29 =head1 SYNOPSIS
  30
  31         perl -MO=Backend[,OPTIONS] foo.pl
  32
  33 =head1 DESCRIPTION
  34
  35 This is the module that is used as a frontend to the Perl Compiler.
  36
  37 =head1 CONVENTIONS
  38
  39 Most compiler backends use the following conventions: OPTIONS
  40 consists of a comma-separated list of words (no white-space).
  41 The C<-v> option usually puts the backend into verbose mode.
  42 The C<-ofile> option generates output to B<file> instead of
  43 stdout. The C<-D> option followed by various letters turns on
  44 various internal debugging flags. See the documentation for the
  45 desired backend (named C<B::Backend> for the example above) to
  46 find out about that backend.
  47
  48 =head1 IMPLEMENTATION
  49
  50 This section is only necessary for those who want to write a
  51 compiler backend module that can be used via this module.
  52
  53 The command-line mentioned in the SYNOPSIS section corresponds to
  54 the Perl code
  55
  56     use O ("Backend", OPTIONS);
  57
  58 The C<import> function which that calls loads in the appropriate
  59 C<B::Backend> module and calls the C<compile> function in that
  60 package, passing it OPTIONS. That function is expected to return
  61 a sub reference which we'll call CALLBACK. Next, the "compile-only"
  62 flag is switched on (equivalent to the command-line option C<-c>)
  63 and a CHECK block is registered which calls CALLBACK. Thus the main
  64 Perl program mentioned on the command-line is read in, parsed and
  65 compiled into internal syntax tree form. Since the C<-c> flag is
  66 set, the program does not start running (excepting BEGIN blocks of
  67 course) but the CALLBACK function registered by the compiler
  68 backend is called.
  69
  70 In summary, a compiler backend module should be called "B::Foo"
  71 for some foo and live in the appropriate directory for that name.
  72 It should define a function called C<compile>. When the user types
  73
  74     perl -MO=Foo,OPTIONS foo.pl
  75
  76 that function is called and is passed those OPTIONS (split on
  77 commas). It should return a sub ref to the main compilation function.
  78 After the user's program is loaded and parsed, that returned sub ref
  79 is invoked which can then go ahead and do the compilation, usually by
  80 making use of the C<B> module's functionality.
  81
  82 =head1 AUTHOR
  83
  84 Malcolm Beattie, C<mbeattie@sable.ox.ac.uk>
  85
  86 =cut