1# include_next.m4 serial 14 2dnl Copyright (C) 2006-2009 Free Software Foundation, Inc. 3dnl This file is free software; the Free Software Foundation 4dnl gives unlimited permission to copy and/or distribute it, 5dnl with or without modifications, as long as this notice is preserved. 6 7dnl From Paul Eggert and Derek Price. 8 9dnl Sets INCLUDE_NEXT and PRAGMA_SYSTEM_HEADER. 10dnl 11dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to 12dnl 'include' otherwise. 13dnl 14dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler 15dnl supports it in the special case that it is the first include directive in 16dnl the given file, or to 'include' otherwise. 17dnl 18dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next, 19dnl so as to avoid GCC warnings when the gcc option -pedantic is used. 20dnl '#pragma GCC system_header' has the same effect as if the file was found 21dnl through the include search path specified with '-isystem' options (as 22dnl opposed to the search path specified with '-I' options). Namely, gcc 23dnl does not warn about some things, and on some systems (Solaris and Interix) 24dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side 25dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead 26dnl of plain '__STDC__'. 27 28AC_DEFUN([gl_INCLUDE_NEXT], 29[ 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 48int foo; 49#else 50#error "include_next doesn't work" 51#endif 52EOF 53 cat <<EOF > conftestd1b/conftest.h 54#define DEFINED_IN_CONFTESTD1 55#include <stdio.h> 56#include_next <conftest.h> 57#ifdef DEFINED_IN_CONFTESTD2 58int foo; 59#else 60#error "include_next doesn't work" 61#endif 62EOF 63 cat <<EOF > conftestd2/conftest.h 64#ifndef DEFINED_IN_CONFTESTD1 65#error "include_next test doesn't work" 66#endif 67#define DEFINED_IN_CONFTESTD2 68EOF 69 gl_save_CPPFLAGS="$CPPFLAGS" 70 CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2" 71 AC_COMPILE_IFELSE([#include <conftest.h>], 72 [gl_cv_have_include_next=yes], 73 [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2" 74 AC_COMPILE_IFELSE([#include <conftest.h>], 75 [gl_cv_have_include_next=buggy], 76 [gl_cv_have_include_next=no]) 77 ]) 78 CPPFLAGS="$gl_save_CPPFLAGS" 79 rm -rf conftestd1a conftestd1b conftestd2 80 ]) 81 PRAGMA_SYSTEM_HEADER= 82 if test $gl_cv_have_include_next = yes; then 83 INCLUDE_NEXT=include_next 84 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next 85 if test -n "$GCC"; then 86 PRAGMA_SYSTEM_HEADER='#pragma GCC system_header' 87 fi 88 else 89 if test $gl_cv_have_include_next = buggy; then 90 INCLUDE_NEXT=include 91 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next 92 else 93 INCLUDE_NEXT=include 94 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include 95 fi 96 fi 97 AC_SUBST([INCLUDE_NEXT]) 98 AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE]) 99 AC_SUBST([PRAGMA_SYSTEM_HEADER]) 100]) 101 102# gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...) 103# ------------------------------------------ 104# For each arg foo.h, if #include_next works, define NEXT_FOO_H to be 105# '<foo.h>'; otherwise define it to be 106# '"///usr/include/foo.h"', or whatever other absolute file name is suitable. 107# Also, if #include_next works as first preprocessing directive in a file, 108# define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to 109# be 110# '"///usr/include/foo.h"', or whatever other absolute file name is suitable. 111# That way, a header file with the following line: 112# #@INCLUDE_NEXT@ @NEXT_FOO_H@ 113# or 114# #@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@ 115# behaves (after sed substitution) as if it contained 116# #include_next <foo.h> 117# even if the compiler does not support include_next. 118# The three "///" are to pacify Sun C 5.8, which otherwise would say 119# "warning: #include of /usr/include/... may be non-portable". 120# Use `""', not `<>', so that the /// cannot be confused with a C99 comment. 121# Note: This macro assumes that the header file is not empty after 122# preprocessing, i.e. it does not only define preprocessor macros but also 123# provides some type/enum definitions or function/variable declarations. 124AC_DEFUN([gl_CHECK_NEXT_HEADERS], 125[ 126 AC_REQUIRE([gl_INCLUDE_NEXT]) 127 AC_REQUIRE([AC_CANONICAL_HOST]) 128 AC_CHECK_HEADERS_ONCE([$1]) 129 130 m4_foreach_w([gl_HEADER_NAME], [$1], 131 [AS_VAR_PUSHDEF([gl_next_header], 132 [gl_cv_next_]m4_defn([gl_HEADER_NAME])) 133 if test $gl_cv_have_include_next = yes; then 134 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>']) 135 else 136 AC_CACHE_CHECK( 137 [absolute name of <]m4_defn([gl_HEADER_NAME])[>], 138 m4_defn([gl_next_header]), 139 [AS_VAR_PUSHDEF([gl_header_exists], 140 [ac_cv_header_]m4_defn([gl_HEADER_NAME])) 141 if test AS_VAR_GET(gl_header_exists) = yes; then 142 AC_LANG_CONFTEST( 143 [AC_LANG_SOURCE( 144 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]] 145 )]) 146 dnl AIX "xlc -E" and "cc -E" omit #line directives for header files 147 dnl that contain only a #include of other header files and no 148 dnl non-comment tokens of their own. This leads to a failure to 149 dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h> 150 dnl and others. The workaround is to force preservation of comments 151 dnl through option -C. This ensures all necessary #line directives 152 dnl are present. GCC supports option -C as well. 153 case "$host_os" in 154 aix*) gl_absname_cpp="$ac_cpp -C" ;; 155 *) gl_absname_cpp="$ac_cpp" ;; 156 esac 157 dnl eval is necessary to expand gl_absname_cpp. 158 dnl Ultrix and Pyramid sh refuse to redirect output of eval, 159 dnl so use subshell. 160 AS_VAR_SET([gl_next_header], 161 ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD | 162 sed -n '\#/]m4_defn([gl_HEADER_NAME])[#{ 163 s#.*"\(.*/]m4_defn([gl_HEADER_NAME])[\)".*#\1# 164 s#^/[^/]#//&# 165 p 166 q 167 }'`'"']) 168 else 169 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>']) 170 fi 171 AS_VAR_POPDEF([gl_header_exists])]) 172 fi 173 AC_SUBST( 174 AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])), 175 [AS_VAR_GET([gl_next_header])]) 176 if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then 177 # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next' 178 gl_next_as_first_directive='<'gl_HEADER_NAME'>' 179 else 180 # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include' 181 gl_next_as_first_directive=AS_VAR_GET([gl_next_header]) 182 fi 183 AC_SUBST( 184 AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])), 185 [$gl_next_as_first_directive]) 186 AS_VAR_POPDEF([gl_next_header])]) 187]) 188