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   1  package O;
   2  
   3  our $VERSION = '1.00';
   4  
   5  use B qw(minus_c save_BEGINs);
   6  use Carp;
   7  
   8  sub import {
   9      my ($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 $@;
  58  }
  59  
  60  1;
  61  
  62  __END__
  63  
  64  =head1 NAME
  65  
  66  O - Generic interface to Perl Compiler backends
  67  
  68  =head1 SYNOPSIS
  69  
  70      perl -MO=[-q,]Backend[,OPTIONS] foo.pl
  71  
  72  =head1 DESCRIPTION
  73  
  74  This is the module that is used as a frontend to the Perl Compiler.
  75  
  76  If you pass the C<-q> option to the module, then the STDOUT
  77  filehandle will be redirected into the variable C<$O::BEGIN_output>
  78  during compilation.  This has the effect that any output printed
  79  to STDOUT by BEGIN blocks or use'd modules will be stored in this
  80  variable rather than printed. It's useful with those backends which
  81  produce output themselves (C<Deparse>, C<Concise> etc), so that
  82  their output is not confused with that generated by the code
  83  being compiled.
  84  
  85  The C<-qq> option behaves like C<-q>, except that it also closes
  86  STDERR after deparsing has finished. This suppresses the "Syntax OK"
  87  message normally produced by perl.
  88  
  89  =head1 CONVENTIONS
  90  
  91  Most compiler backends use the following conventions: OPTIONS
  92  consists of a comma-separated list of words (no white-space).
  93  The C<-v> option usually puts the backend into verbose mode.
  94  The C<-ofile> option generates output to B<file> instead of
  95  stdout. The C<-D> option followed by various letters turns on
  96  various internal debugging flags. See the documentation for the
  97  desired backend (named C<B::Backend> for the example above) to
  98  find out about that backend.
  99  
 100  =head1 IMPLEMENTATION
 101  
 102  This section is only necessary for those who want to write a
 103  compiler backend module that can be used via this module.
 104  
 105  The command-line mentioned in the SYNOPSIS section corresponds to
 106  the Perl code
 107  
 108      use O ("Backend", OPTIONS);
 109  
 110  The C<O::import> function loads the appropriate C<B::Backend> module
 111  and calls its C<compile> function, passing it OPTIONS. That function
 112  is expected to return a sub reference which we'll call CALLBACK. Next,
 113  the "compile-only" flag is switched on (equivalent to the command-line
 114  option C<-c>) and a CHECK block is registered which calls
 115  CALLBACK. Thus the main Perl program mentioned on the command-line is
 116  read in, parsed and compiled into internal syntax tree form. Since the
 117  C<-c> flag is set, the program does not start running (excepting BEGIN
 118  blocks of course) but the CALLBACK function registered by the compiler
 119  backend is called.
 120  
 121  In summary, a compiler backend module should be called "B::Foo"
 122  for some foo and live in the appropriate directory for that name.
 123  It should define a function called C<compile>. When the user types
 124  
 125      perl -MO=Foo,OPTIONS foo.pl
 126  
 127  that function is called and is passed those OPTIONS (split on
 128  commas). It should return a sub ref to the main compilation function.
 129  After the user's program is loaded and parsed, that returned sub ref
 130  is invoked which can then go ahead and do the compilation, usually by
 131  making use of the C<B> module's functionality.
 132  
 133  =head1 BUGS
 134  
 135  The C<-q> and C<-qq> options don't work correctly if perl isn't
 136  compiled with PerlIO support : STDOUT will be closed instead of being
 137  redirected to C<$O::BEGIN_output>.
 138  
 139  =head1 AUTHOR
 140  
 141  Malcolm Beattie, C<mbeattie@sable.ox.ac.uk>
 142  
 143  =cut