+++ /dev/null
-=head1 NAME
-
-perlcompile - Introduction to the Perl Compiler-Translator
-
-=head1 DESCRIPTION
-
-Perl has always had a compiler: your source is compiled into an
-internal form (a parse tree) which is then optimized before being
-run. Since version 5.005, Perl has shipped with a module
-capable of inspecting the optimized parse tree (C<B>), and this has
-been used to write many useful utilities, including a module that lets
-you turn your Perl into C source code that can be compiled into a
-native executable.
-
-The C<B> module provides access to the parse tree, and other modules
-("back ends") do things with the tree. Some write it out as
-semi-human-readable text. Another traverses the parse tree to build a
-cross-reference of which subroutines, formats, and variables are used
-where. Another checks your code for dubious constructs. Yet another back
-end dumps the parse tree back out as Perl source, acting as a source code
-beautifier or deobfuscator.
-
-Because its original purpose was to be a way to produce C code
-corresponding to a Perl program, and in turn a native executable, the
-C<B> module and its associated back ends are known as "the
-compiler", even though they don't really compile anything.
-Different parts of the compiler are more accurately a "translator",
-or an "inspector", but people want Perl to have a "compiler
-option" not an "inspector gadget". What can you do?
-
-This document covers the use of the Perl compiler: which modules
-it comprises, how to use the most important of the back end modules,
-what problems there are, and how to work around them.
-
-=head2 Layout
-
-The compiler back ends are in the C<B::> hierarchy, and the front-end
-(the module that you, the user of the compiler, will sometimes
-interact with) is the O module.
-
-Here are the important back ends to know about, with their status
-expressed as a number from 0 (outline for later implementation) to
-10 (if there's a bug in it, we're very surprised):
-
-=over 4
-
-=item B::Lint
-
-Complains if it finds dubious constructs in your source code. Status:
-6 (it works adequately, but only has a very limited number of areas
-that it checks).
-
-=item B::Deparse
-
-Recreates the Perl source, making an attempt to format it coherently.
-Status: 8 (it works nicely, but a few obscure things are missing).
-
-=item B::Xref
-
-Reports on the declaration and use of subroutines and variables.
-Status: 8 (it works nicely, but still has a few lingering bugs).
-
-=back
-
-=head1 Using The Back Ends
-
-The following sections describe how to use the various compiler back
-ends. They're presented roughly in order of maturity, so that the
-most stable and proven back ends are described first, and the most
-experimental and incomplete back ends are described last.
-
-The O module automatically enabled the B<-c> flag to Perl, which
-prevents Perl from executing your code once it has been compiled.
-This is why all the back ends print:
-
- myperlprogram syntax OK
-
-before producing any other output.
-
-=head2 The Cross-Referencing Back End
-
-The cross-referencing back end (B::Xref) produces a report on your program,
-breaking down declarations and uses of subroutines and variables (and
-formats) by file and subroutine. For instance, here's part of the
-report from the I<pod2man> program that comes with Perl:
-
- Subroutine clear_noremap
- Package (lexical)
- $ready_to_print i1069, 1079
- Package main
- $& 1086
- $. 1086
- $0 1086
- $1 1087
- $2 1085, 1085
- $3 1085, 1085
- $ARGV 1086
- %HTML_Escapes 1085, 1085
-
-This shows the variables used in the subroutine C<clear_noremap>. The
-variable C<$ready_to_print> is a my() (lexical) variable,
-B<i>ntroduced (first declared with my()) on line 1069, and used on
-line 1079. The variable C<$&> from the main package is used on 1086,
-and so on.
-
-A line number may be prefixed by a single letter:
-
-=over 4
-
-=item i
-
-Lexical variable introduced (declared with my()) for the first time.
-
-=item &
-
-Subroutine or method call.
-
-=item s
-
-Subroutine defined.
-
-=item r
-
-Format defined.
-
-=back
-
-The most useful option the cross referencer has is to save the report
-to a separate file. For instance, to save the report on
-I<myperlprogram> to the file I<report>:
-
- $ perl -MO=Xref,-oreport myperlprogram
-
-=head2 The Decompiling Back End
-
-The Deparse back end turns your Perl source back into Perl source. It
-can reformat along the way, making it useful as a deobfuscator. The
-most basic way to use it is:
-
- $ perl -MO=Deparse myperlprogram
-
-You'll notice immediately that Perl has no idea of how to paragraph
-your code. You'll have to separate chunks of code from each other
-with newlines by hand. However, watch what it will do with
-one-liners:
-
- $ perl -MO=Deparse -e '$op=shift||die "usage: $0
- code [...]";chomp(@ARGV=<>)unless@ARGV; for(@ARGV){$was=$_;eval$op;
- die$@ if$@; rename$was,$_ unless$was eq $_}'
- -e syntax OK
- $op = shift @ARGV || die("usage: $0 code [...]");
- chomp(@ARGV = <ARGV>) unless @ARGV;
- foreach $_ (@ARGV) {
- $was = $_;
- eval $op;
- die $@ if $@;
- rename $was, $_ unless $was eq $_;
- }
-
-The decompiler has several options for the code it generates. For
-instance, you can set the size of each indent from 4 (as above) to
-2 with:
-
- $ perl -MO=Deparse,-si2 myperlprogram
-
-The B<-p> option adds parentheses where normally they are omitted:
-
- $ perl -MO=Deparse -e 'print "Hello, world\n"'
- -e syntax OK
- print "Hello, world\n";
- $ perl -MO=Deparse,-p -e 'print "Hello, world\n"'
- -e syntax OK
- print("Hello, world\n");
-
-See L<B::Deparse> for more information on the formatting options.
-
-=head2 The Lint Back End
-
-The lint back end (B::Lint) inspects programs for poor style. One
-programmer's bad style is another programmer's useful tool, so options
-let you select what is complained about.
-
-To run the style checker across your source code:
-
- $ perl -MO=Lint myperlprogram
-
-To disable context checks and undefined subroutines:
-
- $ perl -MO=Lint,-context,-undefined-subs myperlprogram
-
-See L<B::Lint> for information on the options.
-
-=head1 Module List for the Compiler Suite
-
-=over 4
-
-=item B
-
-This module is the introspective ("reflective" in Java terms)
-module, which allows a Perl program to inspect its innards. The
-back end modules all use this module to gain access to the compiled
-parse tree. You, the user of a back end module, will not need to
-interact with B.
-
-=item O
-
-This module is the front-end to the compiler's back ends. Normally
-called something like this:
-
- $ perl -MO=Deparse myperlprogram
-
-This is like saying C<use O 'Deparse'> in your Perl program.
-
-=item B::Concise
-
-This module prints a concise (but complete) version of the Perl parse
-tree. Its output is more customizable than the one of B::Terse or
-B::Debug (and it can emulate them). This module is useful for people who
-are writing their own back end, or who are learning about the Perl
-internals. It's not useful to the average programmer.
-
-=item B::Debug
-
-This module dumps the Perl parse tree in verbose detail to STDOUT.
-It's useful for people who are writing their own back end, or who
-are learning about the Perl internals. It's not useful to the
-average programmer.
-
-=item B::Deparse
-
-This module produces Perl source code from the compiled parse tree.
-It is useful in debugging and deconstructing other people's code,
-also as a pretty-printer for your own source. See
-L</"The Decompiling Back End"> for details about usage.
-
-=item B::Lint
-
-This module inspects the compiled form of your source code for things
-which, while some people frown on them, aren't necessarily bad enough
-to justify a warning. For instance, use of an array in scalar context
-without explicitly saying C<scalar(@array)> is something that Lint
-can identify. See L</"The Lint Back End"> for details about usage.
-
-=item B::Showlex
-
-This module prints out the my() variables used in a function or a
-file. To get a list of the my() variables used in the subroutine
-mysub() defined in the file myperlprogram:
-
- $ perl -MO=Showlex,mysub myperlprogram
-
-To get a list of the my() variables used in the file myperlprogram:
-
- $ perl -MO=Showlex myperlprogram
-
-[BROKEN]
-
-=item B::Terse
-
-This module prints the contents of the parse tree, but without as much
-information as B::Debug. For comparison, C<print "Hello, world.">
-produced 96 lines of output from B::Debug, but only 6 from B::Terse.
-
-This module is useful for people who are writing their own back end,
-or who are learning about the Perl internals. It's not useful to the
-average programmer.
-
-=item B::Xref
-
-This module prints a report on where the variables, subroutines, and
-formats are defined and used within a program and the modules it
-loads. See L</"The Cross-Referencing Back End"> for details about
-usage.
-
-=back
-
-=head1 KNOWN PROBLEMS
-
-BEGIN{} blocks are executed while compiling your code. Any external
-state that is initialized in BEGIN{}, such as opening files, initiating
-database connections etc., do not behave properly. To work around
-this, Perl has an INIT{} block that corresponds to code being executed
-before your program begins running but after your program has finished
-being compiled. Execution order: BEGIN{}, (possible save of state
-through compiler back-end), INIT{}, program runs, END{}.
-
-=head1 AUTHOR
-
-This document was originally written by Nathan Torkington, and is now
-maintained by the perl5-porters mailing list
-I<perl5-porters@perl.org>.
-
-=cut
https://perl5.git.perl.org / perl5.git / commitdiff