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"XIt'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 v5.14.2                                       2013-06-08                      Makefile::AST::Evaluator(3pm)