1 # include_next.m4 serial 11
2 dnl Copyright (C) 2006-2009 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 The include of <stdio.h> is because IBM C 9.0, 10.1 (original
36 dnl versions, prior to 2009-01 updates) on AIX 6.1 supports include_next
37 dnl when used as first preprocessor directive in a file, but not when
38 dnl preceded by another include directive. Additionally, with this same
39 dnl compiler, include_next is a no-op when used in a header file that was
40 dnl included by specifying its absolute file name. Despite these two bugs,
41 dnl include_next is used in the compiler's <math.h>. By virtue of the
42 dnl second bug, we need to use include_next as well in this case.
43 cat <<EOF > conftestd1a/conftest.h
44 #define DEFINED_IN_CONFTESTD1
45 #include_next <conftest.h>
46 #ifdef DEFINED_IN_CONFTESTD2
49 #error "include_next doesn't work"
52 cat <<EOF > conftestd1b/conftest.h
53 #define DEFINED_IN_CONFTESTD1
55 #include_next <conftest.h>
56 #ifdef DEFINED_IN_CONFTESTD2
59 #error "include_next doesn't work"
62 cat <<EOF > conftestd2/conftest.h
63 #ifndef DEFINED_IN_CONFTESTD1
64 #error "include_next test doesn't work"
66 #define DEFINED_IN_CONFTESTD2
68 gl_save_CPPFLAGS="$CPPFLAGS"
69 CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
70 AC_COMPILE_IFELSE([#include <conftest.h>],
71 [gl_cv_have_include_next=yes],
72 [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
73 AC_COMPILE_IFELSE([#include <conftest.h>],
74 [gl_cv_have_include_next=buggy],
75 [gl_cv_have_include_next=no])
77 CPPFLAGS="$gl_save_CPPFLAGS"
78 rm -rf conftestd1a conftestd1b conftestd2
81 if test $gl_cv_have_include_next = yes; then
82 INCLUDE_NEXT=include_next
83 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
84 if test -n "$GCC"; then
85 PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
88 if test $gl_cv_have_include_next = buggy; then
90 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
93 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
96 AC_SUBST([INCLUDE_NEXT])
97 AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
98 AC_SUBST([PRAGMA_SYSTEM_HEADER])
101 # gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
102 # ------------------------------------------
103 # For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
104 # '<foo.h>'; otherwise define it to be
105 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
106 # That way, a header file with the following line:
107 # #@INCLUDE_NEXT@ @NEXT_FOO_H@
108 # behaves (after sed substitution) as if it contained
109 # #include_next <foo.h>
110 # even if the compiler does not support include_next.
111 # The three "///" are to pacify Sun C 5.8, which otherwise would say
112 # "warning: #include of /usr/include/... may be non-portable".
113 # Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
114 # Note: This macro assumes that the header file is not empty after
115 # preprocessing, i.e. it does not only define preprocessor macros but also
116 # provides some type/enum definitions or function/variable declarations.
117 AC_DEFUN([gl_CHECK_NEXT_HEADERS],
119 AC_REQUIRE([gl_INCLUDE_NEXT])
120 AC_REQUIRE([AC_CANONICAL_HOST])
121 AC_CHECK_HEADERS_ONCE([$1])
123 m4_foreach_w([gl_HEADER_NAME], [$1],
124 [AS_VAR_PUSHDEF([gl_next_header],
125 [gl_cv_next_]m4_quote(m4_defn([gl_HEADER_NAME])))
126 if test $gl_cv_have_include_next = yes; then
127 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
130 [absolute name of <]m4_quote(m4_defn([gl_HEADER_NAME]))[>],
131 m4_quote(m4_defn([gl_next_header])),
132 [AS_VAR_PUSHDEF([gl_header_exists],
133 [ac_cv_header_]m4_quote(m4_defn([gl_HEADER_NAME])))
134 if test AS_VAR_GET(gl_header_exists) = yes; then
137 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
139 dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
140 dnl that contain only a #include of other header files and no
141 dnl non-comment tokens of their own. This leads to a failure to
142 dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
143 dnl and others. The workaround is to force preservation of comments
144 dnl through option -C. This ensures all necessary #line directives
145 dnl are present. GCC supports option -C as well.
147 aix*) gl_absname_cpp="$ac_cpp -C" ;;
148 *) gl_absname_cpp="$ac_cpp" ;;
150 dnl eval is necessary to expand gl_absname_cpp.
151 dnl Ultrix and Pyramid sh refuse to redirect output of eval,
153 AS_VAR_SET([gl_next_header],
154 ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
155 sed -n '\#/]m4_quote(m4_defn([gl_HEADER_NAME]))[#{
156 s#.*"\(.*/]m4_quote(m4_defn([gl_HEADER_NAME]))[\)".*#\1#
162 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
164 AS_VAR_POPDEF([gl_header_exists])])
167 AS_TR_CPP([NEXT_]m4_quote(m4_defn([gl_HEADER_NAME]))),
168 [AS_VAR_GET([gl_next_header])])
169 AS_VAR_POPDEF([gl_next_header])])