diff options
Diffstat (limited to 'contrib/perl5/pod/perlcompile.pod')
| -rw-r--r-- | contrib/perl5/pod/perlcompile.pod | 441 |
1 files changed, 0 insertions, 441 deletions
diff --git a/contrib/perl5/pod/perlcompile.pod b/contrib/perl5/pod/perlcompile.pod deleted file mode 100644 index 282592e..0000000 --- a/contrib/perl5/pod/perlcompile.pod +++ /dev/null @@ -1,441 +0,0 @@ -=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 an -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 -bytecode, C source code, or a 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. Some back ends (e.g., C<B::C>) have -programs (e.g., I<perlcc>) to hide the modules' complexity. - -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::Bytecode - -Stores the parse tree in a machine-independent format, suitable -for later reloading through the ByteLoader module. Status: 5 (some -things work, some things don't, some things are untested). - -=item B::C - -Creates a C source file containing code to rebuild the parse tree -and resume the interpreter. Status: 6 (many things work adequately, -including programs using Tk). - -=item B::CC - -Creates a C source file corresponding to the run time code path in -the parse tree. This is the closest to a Perl-to-C translator there -is, but the code it generates is almost incomprehensible because it -translates the parse tree into a giant switch structure that -manipulates Perl structures. Eventual goal is to reduce (given -sufficient type information in the Perl program) some of the -Perl data structure manipulations into manipulations of C-level -ints, floats, etc. Status: 5 (some things work, including -uncomplicated Tk examples). - -=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 de-obfuscator. 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. - -=head2 The Simple C Back End - -This module saves the internal compiled state of your Perl program -to a C source file, which can be turned into a native executable -for that particular platform using a C compiler. The resulting -program links against the Perl interpreter library, so it -will not save you disk space (unless you build Perl with a shared -library) or program size. It may, however, save you startup time. - -The C<perlcc> tool generates such executables by default. - - perlcc myperlprogram.pl - -=head2 The Bytecode Back End - -This back end is only useful if you also have a way to load and -execute the bytecode that it produces. The ByteLoader module provides -this functionality. - -To turn a Perl program into executable byte code, you can use C<perlcc> -with the C<-b> switch: - - perlcc -b myperlprogram.pl - -The byte code is machine independent, so once you have a compiled -module or program, it is as portable as Perl source (assuming that -the user of the module or program has a modern-enough Perl interpreter -to decode the byte code). - -See B<B::Bytecode> for information on options to control the -optimization and nature of the code generated by the Bytecode module. - -=head2 The Optimized C Back End - -The optimized C back end will turn your Perl program's run time -code-path into an equivalent (but optimized) C program that manipulates -the Perl data structures directly. The program will still link against -the Perl interpreter library, to allow for eval(), C<s///e>, -C<require>, etc. - -The C<perlcc> tool generates such executables when using the -opt -switch. To compile a Perl program (ending in C<.pl> -or C<.p>): - - perlcc -opt myperlprogram.pl - -To produce a shared library from a Perl module (ending in C<.pm>): - - perlcc -opt Myperlmodule.pm - -For more information, see L<perlcc> and L<B::CC>. - -=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::Asmdata - -This module is used by the B::Assembler module, which is in turn used -by the B::Bytecode module, which stores a parse-tree as -bytecode for later loading. It's not a back end itself, but rather a -component of a back end. - -=item B::Assembler - -This module turns a parse-tree into data suitable for storing -and later decoding back into a parse-tree. It's not a back end -itself, but rather a component of a back end. It's used by the -I<assemble> program that produces bytecode. - -=item B::Bblock - -This module is used by the B::CC back end. It walks "basic blocks". -A basic block is a series of operations which is known to execute from -start to finish, with no possibility of branching or halting. - -=item B::Bytecode - -This module is a back end that generates bytecode from a -program's parse tree. This bytecode is written to a file, from where -it can later be reconstructed back into a parse tree. The goal is to -do the expensive program compilation once, save the interpreter's -state into a file, and then restore the state from the file when the -program is to be executed. See L</"The Bytecode Back End"> -for details about usage. - -=item B::C - -This module writes out C code corresponding to the parse tree and -other interpreter internal structures. You compile the corresponding -C file, and get an executable file that will restore the internal -structures and the Perl interpreter will begin running the -program. See L</"The Simple C Back End"> for details about usage. - -=item B::CC - -This module writes out C code corresponding to your program's -operations. Unlike the B::C module, which merely stores the -interpreter and its state in a C program, the B::CC module makes a -C program that does not involve the interpreter. As a consequence, -programs translated into C by B::CC can execute faster than normal -interpreted programs. See L</"The Optimized C Back End"> for -details about usage. - -=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::Disassembler - -This module turns bytecode back into a parse tree. It's not a back -end itself, but rather a component of a back end. It's used by the -I<disassemble> program that comes with the bytecode. - -=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::Stackobj - -This module is used by the B::CC module. It's not a back end itself, -but rather a component of a back end. - -=item B::Stash - -This module is used by the L<perlcc> program, which compiles a module -into an executable. B::Stash prints the symbol tables in use by a -program, and is used to prevent B::CC from producing C code for the -B::* and O modules. It's not a back end itself, but rather a -component of a back end. - -=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 - -The simple C backend currently only saves typeglobs with alphanumeric -names. - -The optimized C backend outputs code for more modules than it should -(e.g., DirHandle). It also has little hope of properly handling -C<goto LABEL> outside the running subroutine (C<goto &sub> is okay). -C<goto LABEL> currently does not work at all in this backend. -It also creates a huge initialization function that gives -C compilers headaches. Splitting the initialization function gives -better results. Other problems include: unsigned math does not -work correctly; some opcodes are handled incorrectly by default -opcode handling mechanism. - -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 |
