Makefile::AST::Evaluator(3pm)				User Contributed Perl Documentation			     Makefile::AST::Evaluator(3pm)

NAME

       Makefile::AST::Evaluator - Evaluator and runtime for Makefile::AST instances

SYNOPSIS

	   use Makefile::AST::Evaluator;

	   $Makefile::AST::Evaluator::JustPrint = 0;
	   $Makefile::AST::Evaluator::Quiet = 1;
	   $Makefile::AST::Evaluator::IgnoreErrors = 1;
	   $Makefile::AST::Evaluator::AlwaysMake = 1;
	   $Makefile::AST::Evaluator::Question = 1;

	   # $ast is a Makefile::AST instance:
	   my $eval = Makefile::AST::Evaluator->new($ast);

	   Makefile::AST::Evaluator->add_trigger(
	       firing_rule => sub {
		   my ($self, $rule, $ast_cmds) = @_;
		   my $target = $rule->target;
		   my $colon = $rule->colon;
		   my @normal_prereqs = @{ $rule->normal_prereqs };
		   # ...
	       }
	   );
	   $eval->set_required_target($user_makefile)
	   $eval->make($goal);

DESCRIPTION

       This module implementes an evaluator or a runtime for makefile ASTs represented by Makefile::AST instances.

       It "executes" the specified GNU make AST by the GNU makefile semantics. Note that, "execution" not necessarily mean building a project tree
       by firing makefile rule commands. Actually you can defining your own triggers by calling the add_trigger method. (See the "SYNOPSIS" for
       examples.) In other words, you can do more interesting things like plotting the call path tree of a Makefile using Graphviz, or translating
       the original makefile to another form (like what the makesimple script does).

       It's worth mentioning that, most of the construction algorithm for topological graph s (including implicit rule application) have already
       been implemented in Makefile::AST and its child node classes.

CONFIGURE VARIABLES

       This module provides several package variables (i.e. static class variables) for controlling the behavior of the evaluator.

       Particularly the user needs to set the $AlwaysMake variable to true and $Question to true, if she wants to use the evaluator to do special
       tasks like plotting dependency graphs and translating GNU makefiles to other format.

       Setting $AlwaysMake to true will force the evaluator to ignore the timestamps of external files appeared in the makefiles while setting
       $Question to true will prevent the evaluator from executing the shell commands specified in the makefile rules.

       Here's the detailed listing for all the config variables:

       $Question
	   This variable corresponds to the command-line option "-q" or <--question> in GNU make. Its purpose is to make the evaluator enter the
	   "questioning mode", i.e., a mode in which "make" will never try executing rule commands unless it has to, "and" echoing is suppressed
	   at the same time.

       $AlwaysMake
	   This variable corresponds to the command-line option "-B" or "--always-make". It forces re-constructing all the rule's targets related
	   to the goal, ignoring the timestamp or existence of targets' dependencies.

       $Quiet
	   It corresponds to GNU make's command-line option "-s", "--silent", or "--quiet". Its effect is to cancel the echoing of shell commands
	   being executed.

       $JustPrint
	   This variable corresponds to GNU make's command line option "-n", "--just-print", "--dry-run", or "--recon". Its effect is to print out
	   the shell commands requiring execution but without actually executing them.

       $IgnoreErrors
	   This variable corresponds to GNU make's command line option "-i" or "--ignore-errors"ieXXIt's used to ignore the errors of shell
	   commands being executed during the make process. The default behavior is quitting as soon as a shell command without the "-" modifier
	   fails.

CLASS TRIGGERS

       The "make_by_rule" method of this class defines a trigger named "firing_rule" via the Class::Trait module. Everytime the "make_by_rule"
       method reaches the trigger point, it will invoke the user's processing handler with the following three arguments: the self object, the
       Makefile::AST::Rule object, and the corresponding "Makefile::AST::Command" object in the context.

       By registering his own processing handlers for the "firing_rule" trigger, the user's code can reuse the evaluator to do his own cool things
       without traversing the makefile ASTs himself.

       See the "SYNOPSIS" for code examples.

CODE REPOSITORY

       For the very latest version of this script, check out the source from

       http://github.com/agentzh/makefile-parser-pm <http://github.com/agentzh/makefile-parser-pm>.

       There is anonymous access to all.

AUTHOR

       Zhang "agentzh" Yichun "<agentzh@gmail.com>"

COPYRIGHT AND LICENSE

       Copyright (c) 2007-2008 by Zhang "agentzh" Yichun (agentzh).

       This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO

       Makefile::AST, Makefile::Parser::GmakeDB, pgmake-db, makesimple, Makefile::DOM.

perl v5.12.4							    2011-08-17					     Makefile::AST::Evaluator(3pm)