1Makefile::Parser::GmakeUDsBe(r3)Contributed Perl DocumenMtaakteifoinle::Parser::GmakeDB(3)
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6 Makefile::Parser::GmakeDB - GNU makefile parser using GNU make's
7 database dump
8
10 This document describes Makefile::Parser::GmakeDB 0.216 released on 18
11 November 2014.
12
14 use Makefile::Parser::GmakeDB;
15 my $db_listing = `make --print-data-base -pqRrs -f Makefile`;
16 my $ast = Makefile::Parser::GmakeDB->parse(\$db_listing);
17
19 This module serves as a parser for GNU makefiles. However, it does not
20 parse user's original makefile directly. Instead it uses Makefile::DOM
21 to parse the "data base output listing" produced by GNU make (via its
22 "--print-data-base" option). So essentially it reuses the C
23 implementation of GNU make.
24 This parser has been tested as a component of the pgmake-db utility and
26 has successfully passed 51% of GNU make 3.81's official test suite.
27 The result of the parser is a makefile AST defined by Makefile::AST.
29 The "data base output listing" generated by "make --print-data-base" is
31 a detailed listing for GNU make's internal data structures, which is
32 essentially the AST used by "make". According to GNU make's current
33 maintainer, Paul Smith, this feature is provided primarily for debuging
34 the user's own makefiles, and it also helps the GNU make developer team
35 to diagnose the flaws in make itself. Incidentally this output is
36 conformed to the GNU makefile syntax, and a lot of important
37 information is provided in the form of makefile comments. Therefore, my
38 GmakeDB parser is able to reuse the Makefile::DOM module to parse this
39 output listing.
40 The data base output from GNU make can be divided into several clearly-
42 separated segments. They're file header, "Variables", "Files", "VPATH
43 Search Paths", as well as the last resource stats information.
44 The contents of these segments are mostly obvious. The Files segment
46 may deserve some explanation. It is the place for explict rules.
47 Now let's take the Variables segment as an example to demonstrate the
49 format of the data base listing:
50 # Variables
52 # automatic
54 <D = $(patsubst %/,%,$(dir $<))
55 # automatic
56 ?F = $(notdir $?)
57 # environment
58 DESKTOP_SESSION = default
59 # automatic
60 ?D = $(patsubst %/,%,$(dir $?))
61 # environment
62 GTK_RC_FILES = /etc/gtk/gtkrc:/home/agentz/.gtkrc-1.2-gnome2
63 # environment
64 ...
65 It's shown that the flavor and origin of the makefile variables are
67 given in the previous line as comments. Hence feeding this back into
68 GNU make again makes little sense.
69 Similarly, the Files segment for explicit rules also puts big amount of
71 the important information into makefile comments:
72 # Files
74 # Not a target:
76 bar.c:
77 # Implicit rule search has not been done.
78 # Modification time never checked.
79 # File has not been updated.
80 all: foo.o bar.o
82 # Implicit rule search has been done.
83 # File does not exist.
84 # File has not been updated.
85 # variable set hash-table stats:
86 # Load=0/32=0%, Rehash=0, Collisions=0/0=0%
87 foo.o: foo.c
89 # Implicit rule search has not been done.
90 # Implicit/static pattern stem: `foo'
91 # File does not exist.
92 # File has not been updated.
93 # variable set hash-table stats:
94 # Load=0/32=0%, Rehash=0, Collisions=0/0=0%
95 # commands to execute (from `ex2.mk', line 8):
96 $(CC) -c $(CFLAGS) $< -o $@
97 ...
98 From the previous two data base listing snippets, it's not hard to see
100 that the variable references in rule commands and recursively-expanded
101 variables's values are not expanded.
102 Experiments have shown that GNU make will do implicit rule search for
104 the first rule that needs to, but no more. This behavior means testing
105 our own implicit rule searching algorithm requires specifying at least
106 two goals that require matching.
107
109 GNU make 3.81
110 At least the make executable of GNU make 3.81 is required to work
111 with this module.
112 Makefile::DOM
114
116 • GNU make does not escape meta characters appeared in rule targes
117 and prerequisites in its data base listing. Examples are ":", "\",
118 and "#". This bug has been reported to the GNU make team as
119 "Savannah bug #20067".
120 This bug has not yet been fixed on the "make" side, so I have to
122 work around this issue by preprocessing the data base listing in
123 the makesimple script.
124 • The data base listing produced by GNU make lacks the information
126 regarding the "export" and "unexport" directives. It gives rise to
127 the lack of information in the resulting AST structures constructed
128 by this module. Hence the current AST and runtime do not implement
129 the "export" and "unexport" directives.
130 To make it even worse, there's no known way to work around it.
132 I've already reported this issue to the GNU make team as Savannah
134 bug #20069.
135
137 For the very latest version of this script, check out the source from
138 <http://github.com/agentzh/makefile-parser-pm>.
140 There is anonymous access to all.
142
144 Zhang "agentzh" Yichun "<agentzh@gmail.com>"
145
147 Copyright (c) 2005-2008 by Zhang "agentzh" Yichun (agentzh).
148 This library is free software; you can redistribute it and/or modify it
150 under the same terms as Perl itself.
151
153 Makefile::AST, Makefile::AST::Evaluator, Makefile::DOM, makesimple,
154 pgmake-db.
155perl v5.36.0 2022-07-22 Makefile::Parser::GmakeDB(3)