1 # include_next.m4 serial 15
2 dnl Copyright (C) 2006-2010 Free Software Foundation, Inc.
3 dnl This file is free software; the Free Software Foundation
4 dnl gives unlimited permission to copy and/or distribute it,
5 dnl with or without modifications, as long as this notice is preserved.
7 dnl From Paul Eggert and Derek Price.
9 dnl Sets INCLUDE_NEXT and PRAGMA_SYSTEM_HEADER.
11 dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to
12 dnl 'include' otherwise.
14 dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler
15 dnl supports it in the special case that it is the first include directive in
16 dnl the given file, or to 'include' otherwise.
18 dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next,
19 dnl so as to avoid GCC warnings when the gcc option -pedantic is used.
20 dnl '#pragma GCC system_header' has the same effect as if the file was found
21 dnl through the include search path specified with '-isystem' options (as
22 dnl opposed to the search path specified with '-I' options). Namely, gcc
23 dnl does not warn about some things, and on some systems (Solaris and Interix)
24 dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side
25 dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead
26 dnl of plain '__STDC__'.
28 AC_DEFUN([gl_INCLUDE_NEXT],
30 AC_LANG_PREPROC_REQUIRE()
31 AC_CACHE_CHECK([whether the preprocessor supports include_next],
32 [gl_cv_have_include_next],
33 [rm -rf conftestd1a conftestd1b conftestd2
34 mkdir conftestd1a conftestd1b conftestd2
35 dnl IBM C 9.0, 10.1 (original versions, prior to the 2009-01 updates) on
36 dnl AIX 6.1 support include_next when used as first preprocessor directive
37 dnl in a file, but not when preceded by another include directive. Check
38 dnl for this bug by including <stdio.h>.
39 dnl Additionally, with this same compiler, include_next is a no-op when
40 dnl used in a header file that was included by specifying its absolute
41 dnl file name. Despite these two bugs, include_next is used in the
42 dnl compiler's <math.h>. By virtue of the second bug, we need to use
43 dnl include_next as well in this case.
44 cat <<EOF > conftestd1a/conftest.h
45 #define DEFINED_IN_CONFTESTD1
46 #include_next <conftest.h>
47 #ifdef DEFINED_IN_CONFTESTD2
50 #error "include_next doesn't work"
53 cat <<EOF > conftestd1b/conftest.h
54 #define DEFINED_IN_CONFTESTD1
56 #include_next <conftest.h>
57 #ifdef DEFINED_IN_CONFTESTD2
60 #error "include_next doesn't work"
63 cat <<EOF > conftestd2/conftest.h
64 #ifndef DEFINED_IN_CONFTESTD1
65 #error "include_next test doesn't work"
67 #define DEFINED_IN_CONFTESTD2
69 gl_save_CPPFLAGS="$CPPFLAGS"
70 CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
71 dnl We intentionally avoid using AC_LANG_SOURCE here.
72 AC_COMPILE_IFELSE([AC_LANG_DEFINES_PROVIDED[#include <conftest.h>]],
73 [gl_cv_have_include_next=yes],
74 [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
75 AC_COMPILE_IFELSE([AC_LANG_DEFINES_PROVIDED[#include <conftest.h>]],
76 [gl_cv_have_include_next=buggy],
77 [gl_cv_have_include_next=no])
79 CPPFLAGS="$gl_save_CPPFLAGS"
80 rm -rf conftestd1a conftestd1b conftestd2
83 if test $gl_cv_have_include_next = yes; then
84 INCLUDE_NEXT=include_next
85 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
86 if test -n "$GCC"; then
87 PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
90 if test $gl_cv_have_include_next = buggy; then
92 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
95 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
98 AC_SUBST([INCLUDE_NEXT])
99 AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
100 AC_SUBST([PRAGMA_SYSTEM_HEADER])
103 # gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
104 # ------------------------------------------
105 # For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
106 # '<foo.h>'; otherwise define it to be
107 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
108 # Also, if #include_next works as first preprocessing directive in a file,
109 # define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to
111 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
112 # That way, a header file with the following line:
113 # #@INCLUDE_NEXT@ @NEXT_FOO_H@
115 # #@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@
116 # behaves (after sed substitution) as if it contained
117 # #include_next <foo.h>
118 # even if the compiler does not support include_next.
119 # The three "///" are to pacify Sun C 5.8, which otherwise would say
120 # "warning: #include of /usr/include/... may be non-portable".
121 # Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
122 # Note: This macro assumes that the header file is not empty after
123 # preprocessing, i.e. it does not only define preprocessor macros but also
124 # provides some type/enum definitions or function/variable declarations.
125 AC_DEFUN([gl_CHECK_NEXT_HEADERS],
127 AC_REQUIRE([gl_INCLUDE_NEXT])
128 AC_REQUIRE([AC_CANONICAL_HOST])
129 AC_CHECK_HEADERS_ONCE([$1])
131 m4_foreach_w([gl_HEADER_NAME], [$1],
132 [AS_VAR_PUSHDEF([gl_next_header],
133 [gl_cv_next_]m4_defn([gl_HEADER_NAME]))
134 if test $gl_cv_have_include_next = yes; then
135 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
138 [absolute name of <]m4_defn([gl_HEADER_NAME])[>],
139 m4_defn([gl_next_header]),
140 [AS_VAR_PUSHDEF([gl_header_exists],
141 [ac_cv_header_]m4_defn([gl_HEADER_NAME]))
142 if test AS_VAR_GET(gl_header_exists) = yes; then
145 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
147 dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
148 dnl that contain only a #include of other header files and no
149 dnl non-comment tokens of their own. This leads to a failure to
150 dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
151 dnl and others. The workaround is to force preservation of comments
152 dnl through option -C. This ensures all necessary #line directives
153 dnl are present. GCC supports option -C as well.
155 aix*) gl_absname_cpp="$ac_cpp -C" ;;
156 *) gl_absname_cpp="$ac_cpp" ;;
158 dnl eval is necessary to expand gl_absname_cpp.
159 dnl Ultrix and Pyramid sh refuse to redirect output of eval,
161 AS_VAR_SET([gl_next_header],
162 ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
163 sed -n '\#/]m4_defn([gl_HEADER_NAME])[#{
164 s#.*"\(.*/]m4_defn([gl_HEADER_NAME])[\)".*#\1#
170 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
172 AS_VAR_POPDEF([gl_header_exists])])
175 AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),
176 [AS_VAR_GET([gl_next_header])])
177 if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then
178 # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next'
179 gl_next_as_first_directive='<'gl_HEADER_NAME'>'
181 # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include'
182 gl_next_as_first_directive=AS_VAR_GET([gl_next_header])
185 AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])),
186 [$gl_next_as_first_directive])
187 AS_VAR_POPDEF([gl_next_header])])
190 # Autoconf 2.68 added warnings for our use of AC_COMPILE_IFELSE;
191 # this fallback is safe for all earlier autoconf versions.
192 m4_define_default([AC_LANG_DEFINES_PROVIDED])