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1 # include_next.m4 serial 10
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2 dnl Copyright (C) 2006-2008 Free Software Foundation, Inc.
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3 dnl This file is free software; the Free Software Foundation
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4 dnl gives unlimited permission to copy and/or distribute it,
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5 dnl with or without modifications, as long as this notice is preserved.
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6
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7 dnl From Paul Eggert and Derek Price.
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8
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9 dnl Sets INCLUDE_NEXT and PRAGMA_SYSTEM_HEADER.
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10 dnl
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11 dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to
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12 dnl 'include' otherwise.
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13 dnl
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14 dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler
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15 dnl supports it in the special case that it is the first include directive in
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16 dnl the given file, or to 'include' otherwise.
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17 dnl
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18 dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next,
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19 dnl so as to avoid GCC warnings when the gcc option -pedantic is used.
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20 dnl '#pragma GCC system_header' has the same effect as if the file was found
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21 dnl through the include search path specified with '-isystem' options (as
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22 dnl opposed to the search path specified with '-I' options). Namely, gcc
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23 dnl does not warn about some things, and on some systems (Solaris and Interix)
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24 dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side
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25 dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead
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26 dnl of plain '__STDC__'.
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27
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28 AC_DEFUN([gl_INCLUDE_NEXT],
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29 [
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30 AC_LANG_PREPROC_REQUIRE()
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31 AC_CACHE_CHECK([whether the preprocessor supports include_next],
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32 [gl_cv_have_include_next],
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33 [rm -rf conftestd1a conftestd1b conftestd2
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34 mkdir conftestd1a conftestd1b conftestd2
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35 dnl The include of <stdio.h> is because IBM C 9.0 on AIX 6.1 supports
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36 dnl include_next when used as first preprocessor directive in a file,
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37 dnl but not when preceded by another include directive. Additionally,
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38 dnl with this same compiler, include_next is a no-op when used in a
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39 dnl header file that was included by specifying its absolute file name.
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40 dnl Despite these two bugs, include_next is used in the compiler's
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41 dnl <math.h>. By virtue of the second bug, we need to use include_next
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42 dnl as well in this case.
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43 cat <<EOF > conftestd1a/conftest.h
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44 #define DEFINED_IN_CONFTESTD1
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45 #include_next <conftest.h>
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46 #ifdef DEFINED_IN_CONFTESTD2
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47 int foo;
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48 #else
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49 #error "include_next doesn't work"
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50 #endif
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51 EOF
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52 cat <<EOF > conftestd1b/conftest.h
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53 #define DEFINED_IN_CONFTESTD1
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54 #include <stdio.h>
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55 #include_next <conftest.h>
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56 #ifdef DEFINED_IN_CONFTESTD2
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57 int foo;
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58 #else
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59 #error "include_next doesn't work"
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60 #endif
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61 EOF
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62 cat <<EOF > conftestd2/conftest.h
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63 #ifndef DEFINED_IN_CONFTESTD1
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64 #error "include_next test doesn't work"
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65 #endif
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66 #define DEFINED_IN_CONFTESTD2
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67 EOF
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68 gl_save_CPPFLAGS="$CPPFLAGS"
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69 CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
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70 AC_COMPILE_IFELSE([#include <conftest.h>],
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71 [gl_cv_have_include_next=yes],
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72 [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
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73 AC_COMPILE_IFELSE([#include <conftest.h>],
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74 [gl_cv_have_include_next=buggy],
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75 [gl_cv_have_include_next=no])
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76 ])
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77 CPPFLAGS="$gl_save_CPPFLAGS"
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78 rm -rf conftestd1a conftestd1b conftestd2
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79 ])
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80 PRAGMA_SYSTEM_HEADER=
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81 if test $gl_cv_have_include_next = yes; then
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82 INCLUDE_NEXT=include_next
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83 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
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84 if test -n "$GCC"; then
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85 PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
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86 fi
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87 else
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88 if test $gl_cv_have_include_next = buggy; then
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89 INCLUDE_NEXT=include
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90 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
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91 else
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92 INCLUDE_NEXT=include
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93 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
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94 fi
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95 fi
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96 AC_SUBST([INCLUDE_NEXT])
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97 AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
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98 AC_SUBST([PRAGMA_SYSTEM_HEADER])
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99 ])
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100
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101 # gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
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102 # ------------------------------------------
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103 # For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
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104 # '<foo.h>'; otherwise define it to be
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105 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
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106 # That way, a header file with the following line:
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107 # #@INCLUDE_NEXT@ @NEXT_FOO_H@
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108 # behaves (after sed substitution) as if it contained
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109 # #include_next <foo.h>
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110 # even if the compiler does not support include_next.
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111 # The three "///" are to pacify Sun C 5.8, which otherwise would say
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112 # "warning: #include of /usr/include/... may be non-portable".
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113 # Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
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114 # Note: This macro assumes that the header file is not empty after
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115 # preprocessing, i.e. it does not only define preprocessor macros but also
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116 # provides some type/enum definitions or function/variable declarations.
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117 AC_DEFUN([gl_CHECK_NEXT_HEADERS],
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118 [
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119 AC_REQUIRE([gl_INCLUDE_NEXT])
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120 AC_REQUIRE([AC_CANONICAL_HOST])
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121 AC_CHECK_HEADERS_ONCE([$1])
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122
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123 m4_foreach_w([gl_HEADER_NAME], [$1],
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124 [AS_VAR_PUSHDEF([gl_next_header],
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125 [gl_cv_next_]m4_quote(m4_defn([gl_HEADER_NAME])))
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126 if test $gl_cv_have_include_next = yes; then
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127 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
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128 else
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129 AC_CACHE_CHECK(
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130 [absolute name of <]m4_quote(m4_defn([gl_HEADER_NAME]))[>],
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131 m4_quote(m4_defn([gl_next_header])),
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132 [AS_VAR_PUSHDEF([gl_header_exists],
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133 [ac_cv_header_]m4_quote(m4_defn([gl_HEADER_NAME])))
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134 if test AS_VAR_GET(gl_header_exists) = yes; then
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135 AC_LANG_CONFTEST(
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136 [AC_LANG_SOURCE(
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137 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
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138 )])
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139 dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
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140 dnl that contain only a #include of other header files and no
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141 dnl non-comment tokens of their own. This leads to a failure to
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142 dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
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143 dnl and others. The workaround is to force preservation of comments
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144 dnl through option -C. This ensures all necessary #line directives
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145 dnl are present. GCC supports option -C as well.
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146 case "$host_os" in
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147 aix*) gl_absname_cpp="$ac_cpp -C" ;;
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148 *) gl_absname_cpp="$ac_cpp" ;;
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149 esac
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150 dnl eval is necessary to expand gl_absname_cpp.
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151 dnl Ultrix and Pyramid sh refuse to redirect output of eval,
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152 dnl so use subshell.
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153 AS_VAR_SET([gl_next_header],
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154 ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
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155 sed -n '\#/]m4_quote(m4_defn([gl_HEADER_NAME]))[#{
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156 s#.*"\(.*/]m4_quote(m4_defn([gl_HEADER_NAME]))[\)".*#\1#
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157 s#^/[^/]#//&#
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158 p
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159 q
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160 }'`'"'])
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161 else
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162 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
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163 fi
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164 AS_VAR_POPDEF([gl_header_exists])])
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165 fi
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166 AC_SUBST(
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167 AS_TR_CPP([NEXT_]m4_quote(m4_defn([gl_HEADER_NAME]))),
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168 [AS_VAR_GET([gl_next_header])])
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169 AS_VAR_POPDEF([gl_next_header])])
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170 ])
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