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a798dbf2 1package O;
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JH
2
3our $VERSION = '1.00';
4
059a8bb7 5use B qw(minus_c save_BEGINs);
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6use Carp;
7
8sub import {
34a48b4b 9 my ($class, @options) = @_;
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10 my ($quiet, $veryquiet) = (0, 0);
11 if ($options[0] eq '-q' || $options[0] eq '-qq') {
34a48b4b 12 $quiet = 1;
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13 open (SAVEOUT, ">&STDOUT");
14 close STDOUT;
15 open (STDOUT, ">", \$O::BEGIN_output);
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16 if ($options[0] eq '-qq') {
17 $veryquiet = 1;
18 }
19 shift @options;
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20 }
21 my $backend = shift (@options);
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22 eval q[
23 BEGIN {
24 minus_c;
25 save_BEGINs;
26 }
27
28 CHECK {
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29 if ($quiet) {
30 close STDOUT;
31 open (STDOUT, ">&SAVEOUT");
32 close SAVEOUT;
33 }
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34 use B::].$backend.q[ ();
35 if ($@) {
36 croak "use of backend $backend failed: $@";
37 }
38
39
40 my $compilesub = &{"B::${backend}::compile"}(@options);
41 if (ref($compilesub) ne "CODE") {
42 die $compilesub;
43 }
44
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45 local $savebackslash = $\;
46 local ($\,$",$,) = (undef,' ','');
7a9b44b9 47 &$compilesub();
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48
49 close STDERR if $veryquiet;
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50 }
51 ];
52 die $@ if $@;
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53}
54
551;
56
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57__END__
58
59=head1 NAME
60
61O - Generic interface to Perl Compiler backends
62
63=head1 SYNOPSIS
64
34a48b4b 65 perl -MO=[-q,]Backend[,OPTIONS] foo.pl
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66
67=head1 DESCRIPTION
68
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69This is the module that is used as a frontend to the Perl Compiler.
70
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71If you pass the C<-q> option to the module, then the STDOUT
72filehandle will be redirected into the variable C<$O::BEGIN_output>
73during compilation. This has the effect that any output printed
74to STDOUT by BEGIN blocks or use'd modules will be stored in this
75variable rather than printed. It's useful with those backends which
76produce output themselves (C<Deparse>, C<Concise> etc), so that
77their output is not confused with that generated by the code
78being compiled.
79
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80The C<-qq> option behaves like C<-q>, except that it also closes
81STDERR after deparsing has finished. This suppresses the "Syntax OK"
82message normally produced by perl.
83
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84=head1 CONVENTIONS
85
86Most compiler backends use the following conventions: OPTIONS
87consists of a comma-separated list of words (no white-space).
88The C<-v> option usually puts the backend into verbose mode.
89The C<-ofile> option generates output to B<file> instead of
90stdout. The C<-D> option followed by various letters turns on
91various internal debugging flags. See the documentation for the
92desired backend (named C<B::Backend> for the example above) to
93find out about that backend.
94
95=head1 IMPLEMENTATION
96
97This section is only necessary for those who want to write a
98compiler backend module that can be used via this module.
99
100The command-line mentioned in the SYNOPSIS section corresponds to
101the Perl code
102
103 use O ("Backend", OPTIONS);
104
105The C<import> function which that calls loads in the appropriate
106C<B::Backend> module and calls the C<compile> function in that
107package, passing it OPTIONS. That function is expected to return
108a sub reference which we'll call CALLBACK. Next, the "compile-only"
109flag is switched on (equivalent to the command-line option C<-c>)
7d30b5c4 110and a CHECK block is registered which calls CALLBACK. Thus the main
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111Perl program mentioned on the command-line is read in, parsed and
112compiled into internal syntax tree form. Since the C<-c> flag is
113set, the program does not start running (excepting BEGIN blocks of
114course) but the CALLBACK function registered by the compiler
115backend is called.
116
117In summary, a compiler backend module should be called "B::Foo"
118for some foo and live in the appropriate directory for that name.
119It should define a function called C<compile>. When the user types
120
121 perl -MO=Foo,OPTIONS foo.pl
122
123that function is called and is passed those OPTIONS (split on
124commas). It should return a sub ref to the main compilation function.
125After the user's program is loaded and parsed, that returned sub ref
126is invoked which can then go ahead and do the compilation, usually by
127making use of the C<B> module's functionality.
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128
129=head1 AUTHOR
130
131Malcolm Beattie, C<mbeattie@sable.ox.ac.uk>
132
133=cut