NAME¶
Makefile::Parser::GmakeDB - GNU makefile parser using GNU make's database dump
VERSION¶
This document describes Makefile::Parser::GmakeDB 0.215 released on 18 August
2011.
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 debugging 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 explicit 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
targets 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.
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) 2005-2008 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::AST::Evaluator, Makefile::DOM, makesimple,
pgmake-db.