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