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date Sun, 16 Aug 2009 17:16:49 +0000
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1 # onceonly.m4 serial 6
2 dnl Copyright (C) 2002-2003, 2005-2006, 2008 Free Software Foundation, Inc.
3 dnl This file is free software, distributed under the terms of the GNU
4 dnl General Public License. As a special exception to the GNU General
5 dnl Public License, this file may be distributed as part of a program
6 dnl that contains a configuration script generated by Autoconf, under
7 dnl the same distribution terms as the rest of that program.
8
9 dnl This file defines some "once only" variants of standard autoconf macros.
10 dnl AC_CHECK_HEADERS_ONCE like AC_CHECK_HEADERS
11 dnl AC_CHECK_FUNCS_ONCE like AC_CHECK_FUNCS
12 dnl AC_CHECK_DECLS_ONCE like AC_CHECK_DECLS
13 dnl AC_REQUIRE([AC_FUNC_STRCOLL]) like AC_FUNC_STRCOLL
14 dnl The advantage is that the check for each of the headers/functions/decls
15 dnl will be put only once into the 'configure' file. It keeps the size of
16 dnl the 'configure' file down, and avoids redundant output when 'configure'
17 dnl is run.
18 dnl The drawback is that the checks cannot be conditionalized. If you write
19 dnl if some_condition; then gl_CHECK_HEADERS(stdlib.h); fi
20 dnl inside an AC_DEFUNed function, the gl_CHECK_HEADERS macro call expands to
21 dnl empty, and the check will be inserted before the body of the AC_DEFUNed
22 dnl function.
23
24 dnl The original code implemented AC_CHECK_HEADERS_ONCE and AC_CHECK_FUNCS_ONCE
25 dnl in terms of AC_DEFUN and AC_REQUIRE. This implementation uses diversions to
26 dnl named sections DEFAULTS and INIT_PREPARE in order to check all requested
27 dnl headers at once, thus reducing the size of 'configure'. It is known to work
28 dnl with autoconf 2.57..2.62 at least . The size reduction is ca. 9%.
29
30 dnl Autoconf version 2.59 plus gnulib is required; this file is not needed
31 dnl with Autoconf 2.60 or greater. But note that autoconf's implementation of
32 dnl AC_CHECK_DECLS_ONCE expects a comma-separated list of symbols as first
33 dnl argument!
34 AC_PREREQ([2.59])
35
36 # AC_CHECK_HEADERS_ONCE(HEADER1 HEADER2 ...) is a once-only variant of
37 # AC_CHECK_HEADERS(HEADER1 HEADER2 ...).
38 AC_DEFUN([AC_CHECK_HEADERS_ONCE], [
39 :
40 m4_foreach_w([gl_HEADER_NAME], [$1], [
41 AC_DEFUN([gl_CHECK_HEADER_]m4_quote(translit(gl_HEADER_NAME,
42 [./-], [___])), [
43 m4_divert_text([INIT_PREPARE],
44 [gl_header_list="$gl_header_list gl_HEADER_NAME"])
45 gl_HEADERS_EXPANSION
46 AH_TEMPLATE(AS_TR_CPP([HAVE_]m4_defn([gl_HEADER_NAME])),
47 [Define to 1 if you have the <]m4_defn([gl_HEADER_NAME])[> header file.])
48 ])
49 AC_REQUIRE([gl_CHECK_HEADER_]m4_quote(translit(gl_HEADER_NAME,
50 [./-], [___])))
51 ])
52 ])
53 m4_define([gl_HEADERS_EXPANSION], [
54 m4_divert_text([DEFAULTS], [gl_header_list=])
55 AC_CHECK_HEADERS([$gl_header_list])
56 m4_define([gl_HEADERS_EXPANSION], [])
57 ])
58
59 # AC_CHECK_FUNCS_ONCE(FUNC1 FUNC2 ...) is a once-only variant of
60 # AC_CHECK_FUNCS(FUNC1 FUNC2 ...).
61 AC_DEFUN([AC_CHECK_FUNCS_ONCE], [
62 :
63 m4_foreach_w([gl_FUNC_NAME], [$1], [
64 AC_DEFUN([gl_CHECK_FUNC_]m4_defn([gl_FUNC_NAME]), [
65 m4_divert_text([INIT_PREPARE],
66 [gl_func_list="$gl_func_list gl_FUNC_NAME"])
67 gl_FUNCS_EXPANSION
68 AH_TEMPLATE(AS_TR_CPP([HAVE_]m4_defn([gl_FUNC_NAME])),
69 [Define to 1 if you have the `]m4_defn([gl_FUNC_NAME])[' function.])
70 ])
71 AC_REQUIRE([gl_CHECK_FUNC_]m4_defn([gl_FUNC_NAME]))
72 ])
73 ])
74 m4_define([gl_FUNCS_EXPANSION], [
75 m4_divert_text([DEFAULTS], [gl_func_list=])
76 AC_CHECK_FUNCS([$gl_func_list])
77 m4_define([gl_FUNCS_EXPANSION], [])
78 ])
79
80 # AC_CHECK_DECLS_ONCE(DECL1 DECL2 ...) is a once-only variant of
81 # AC_CHECK_DECLS(DECL1, DECL2, ...).
82 AC_DEFUN([AC_CHECK_DECLS_ONCE], [
83 :
84 m4_foreach_w([gl_DECL_NAME], [$1], [
85 AC_DEFUN([gl_CHECK_DECL_]m4_defn([gl_DECL_NAME]), [
86 AC_CHECK_DECLS(m4_defn([gl_DECL_NAME]))
87 ])
88 AC_REQUIRE([gl_CHECK_DECL_]m4_defn([gl_DECL_NAME]))
89 ])
90 ])