Makefile::Parser::GmakUser3Contributed Perl DocumeMakefile::Parser::GmakeDB(3)NAMEMakefile::Parser::GmakeDB - GNU makefile parser using GNU make's
database dump
VERSION
This document describes Makefile::Parser::GmakeDB 0.211 released on
March 16, 2008.
SYNOPSIS
use Makefile::Parser::GmakeDB;
my $db_listing = `make --print-data-base -pqRrs -f Makefile`;
my $ast = Makefile::Parser::GmakeDB->parse(\$db_listing);
DESCRIPTION
This module serves as a parser for GNU makefiles. However, it does not
parse user's original makefile directly. Instead it uses Makefile::DOM
to parse the "data base output listing" produced by GNU make (via its
"--print-data-base" option). So essentially it reuses the C
implementation of GNU make.
This parser has been tested as a component of the pgmake-db utility and
has successfully passed 51% of GNU make 3.81's official test suite.
The result of the parser is a makefile AST defined by Makefile::AST.
The "data base output listing" generated by "make --print-data-base" is
a detailed listing for GNU make's internal data structures, which is
essentially the AST used by "make". According to GNU make's current
maintainer, Paul Smith, this feature is provided primarily for debuging
the user's own makefiles, and it also helps the GNU make developer team
to diagnose the flaws in make itself. Incidentally this output is
conformed to the GNU makefile syntax, and a lot of important
information is provided in the form of makefile comments. Therefore, my
GmakeDB parser is able to reuse the Makefile::DOM module to parse this
output listing.
The data base output from GNU make can be divided into several clearly-
separated segments. They're file header, "Variables", "Files", "VPATH
Search Paths", as well as the last resource stats information.
The contents of these segments are mostly obvious. The Files segment
may deserve some explanation. It is the place for explict rules.
Now let's take the Variables segment as an example to demonstrate the
format of the data base listing:
# Variables
# automatic
<D = $(patsubst %/,%,$(dir $<))
# automatic
?F = $(notdir $?)
# environment
DESKTOP_SESSION = default
# automatic
?D = $(patsubst %/,%,$(dir $?))
# environment
GTK_RC_FILES = /etc/gtk/gtkrc:/home/agentz/.gtkrc-1.2-gnome2
# environment
...
It's shown that the flavor and origin of the makefile variables are
given in the previous line as comments. Hence feeding this back into
GNU make again makes little sense.
Similarly, the Files segment for explicit rules also puts big amount of
the important information into makefile comments:
# Files
# Not a target:
bar.c:
# Implicit rule search has not been done.
# Modification time never checked.
# File has not been updated.
all: foo.o bar.o
# Implicit rule search has been done.
# File does not exist.
# File has not been updated.
# variable set hash-table stats:
# Load=0/32=0%, Rehash=0, Collisions=0/0=0%
foo.o: foo.c
# Implicit rule search has not been done.
# Implicit/static pattern stem: `foo'
# File does not exist.
# File has not been updated.
# variable set hash-table stats:
# Load=0/32=0%, Rehash=0, Collisions=0/0=0%
# commands to execute (from `ex2.mk', line 8):
$(CC) -c $(CFLAGS) $< -o $@
...
From the previous two data base listing snippets, it's not hard to see
that the variable references in rule commands and recursively-expanded
variables's values are not expanded.
Experiments have shown that GNU make will do implicit rule search for
the first rule that needs to, but no more. This behavior means testing
our own implicit rule searching algorithm requires specifying at least
two goals that require matching.
DEPENDENCIES
GNU make 3.81
At least the make executable of GNU make 3.81 is required to work
with this module.
Makefile::DOM
BUGS
· GNU make does not escape meta characters appeared in rule targes
and prerequisites in its data base listing. Examples are ":", "\",
and "#". This bug has been reported to the GNU make team as
"Savannah bug #20067".
This bug has not yet been fixed on the "make" side, so I have to
work around this issue by preprocessing the data base listing in
the makesimple script.
· The data base listing produced by GNU make lacks the information
regarding the "export" and "unexport" directives. It gives rise to
the lack of information in the resulting AST structures constructed
by this module. Hence the current AST and runtime do not implement
the "export" and "unexport" directives.
To make it even worse, there's no known way to work around it.
I've already reported this issue to the GNU make team as Savannah
bug #20069.
SVN REPOSITORY
For the very latest version of this script, check out the source from
http://svn.openfoundry.org/makefileparser/branches/gmake-db
<http://svn.openfoundry.org/makefileparser/branches/gmake-db>.
There is anonymous access to all.
AUTHOR
Agent Zhang "<agentzh@yahoo.cn>"
COPYRIGHT AND LICENSE
Copyright (c) 2005-2008 by Agent Zhang (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::AST::Evaluator, Makefile::DOM, makesimple,
pgmake-db.
perl v5.14.1 2008-03-16 Makefile::Parser::GmakeDB(3)
