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1 # include_next.m4 serial 14
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2 dnl Copyright (C) 2006-2010 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 IBM C 9.0, 10.1 (original versions, prior to the 2009-01 updates) on
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36 dnl AIX 6.1 support include_next when used as first preprocessor directive
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37 dnl in a file, but not when preceded by another include directive. Check
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38 dnl for this bug by including <stdio.h>.
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39 dnl Additionally, with this same compiler, include_next is a no-op when
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40 dnl used in a header file that was included by specifying its absolute
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41 dnl file name. Despite these two bugs, include_next is used in the
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42 dnl compiler's <math.h>. By virtue of the second bug, we need to use
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43 dnl include_next as well in this case.
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44 cat <<EOF > conftestd1a/conftest.h
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45 #define DEFINED_IN_CONFTESTD1
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46 #include_next <conftest.h>
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47 #ifdef DEFINED_IN_CONFTESTD2
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48 int foo;
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49 #else
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50 #error "include_next doesn't work"
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51 #endif
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52 EOF
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53 cat <<EOF > conftestd1b/conftest.h
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54 #define DEFINED_IN_CONFTESTD1
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55 #include <stdio.h>
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56 #include_next <conftest.h>
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57 #ifdef DEFINED_IN_CONFTESTD2
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58 int foo;
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59 #else
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60 #error "include_next doesn't work"
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61 #endif
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62 EOF
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63 cat <<EOF > conftestd2/conftest.h
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64 #ifndef DEFINED_IN_CONFTESTD1
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65 #error "include_next test doesn't work"
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66 #endif
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67 #define DEFINED_IN_CONFTESTD2
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68 EOF
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69 gl_save_CPPFLAGS="$CPPFLAGS"
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70 CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
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71 AC_COMPILE_IFELSE([#include <conftest.h>],
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72 [gl_cv_have_include_next=yes],
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73 [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
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74 AC_COMPILE_IFELSE([#include <conftest.h>],
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75 [gl_cv_have_include_next=buggy],
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76 [gl_cv_have_include_next=no])
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77 ])
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78 CPPFLAGS="$gl_save_CPPFLAGS"
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79 rm -rf conftestd1a conftestd1b conftestd2
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80 ])
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81 PRAGMA_SYSTEM_HEADER=
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82 if test $gl_cv_have_include_next = yes; then
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83 INCLUDE_NEXT=include_next
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84 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
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85 if test -n "$GCC"; then
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86 PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
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87 fi
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88 else
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89 if test $gl_cv_have_include_next = buggy; then
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90 INCLUDE_NEXT=include
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91 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
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92 else
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93 INCLUDE_NEXT=include
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94 INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
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95 fi
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96 fi
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97 AC_SUBST([INCLUDE_NEXT])
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98 AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
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99 AC_SUBST([PRAGMA_SYSTEM_HEADER])
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100 ])
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101
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102 # gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
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103 # ------------------------------------------
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104 # For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
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105 # '<foo.h>'; otherwise define it to be
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106 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
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107 # Also, if #include_next works as first preprocessing directive in a file,
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108 # define NEXT_AS_FIRST_DIRECTIVE_FOO_H to be '<foo.h>'; otherwise define it to
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109 # be
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110 # '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
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111 # That way, a header file with the following line:
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112 # #@INCLUDE_NEXT@ @NEXT_FOO_H@
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113 # or
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114 # #@INCLUDE_NEXT_AS_FIRST_DIRECTIVE@ @NEXT_AS_FIRST_DIRECTIVE_FOO_H@
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115 # behaves (after sed substitution) as if it contained
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116 # #include_next <foo.h>
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117 # even if the compiler does not support include_next.
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118 # The three "///" are to pacify Sun C 5.8, which otherwise would say
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119 # "warning: #include of /usr/include/... may be non-portable".
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120 # Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
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121 # Note: This macro assumes that the header file is not empty after
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122 # preprocessing, i.e. it does not only define preprocessor macros but also
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123 # provides some type/enum definitions or function/variable declarations.
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124 AC_DEFUN([gl_CHECK_NEXT_HEADERS],
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125 [
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126 AC_REQUIRE([gl_INCLUDE_NEXT])
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127 AC_REQUIRE([AC_CANONICAL_HOST])
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128 AC_CHECK_HEADERS_ONCE([$1])
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129
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130 m4_foreach_w([gl_HEADER_NAME], [$1],
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131 [AS_VAR_PUSHDEF([gl_next_header],
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132 [gl_cv_next_]m4_defn([gl_HEADER_NAME]))
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133 if test $gl_cv_have_include_next = yes; then
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134 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
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135 else
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136 AC_CACHE_CHECK(
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137 [absolute name of <]m4_defn([gl_HEADER_NAME])[>],
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138 m4_defn([gl_next_header]),
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139 [AS_VAR_PUSHDEF([gl_header_exists],
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140 [ac_cv_header_]m4_defn([gl_HEADER_NAME]))
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141 if test AS_VAR_GET(gl_header_exists) = yes; then
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142 AC_LANG_CONFTEST(
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143 [AC_LANG_SOURCE(
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144 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
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145 )])
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146 dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
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147 dnl that contain only a #include of other header files and no
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148 dnl non-comment tokens of their own. This leads to a failure to
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149 dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
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150 dnl and others. The workaround is to force preservation of comments
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151 dnl through option -C. This ensures all necessary #line directives
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152 dnl are present. GCC supports option -C as well.
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153 case "$host_os" in
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154 aix*) gl_absname_cpp="$ac_cpp -C" ;;
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155 *) gl_absname_cpp="$ac_cpp" ;;
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156 esac
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157 dnl eval is necessary to expand gl_absname_cpp.
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158 dnl Ultrix and Pyramid sh refuse to redirect output of eval,
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159 dnl so use subshell.
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160 AS_VAR_SET([gl_next_header],
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161 ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
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162 sed -n '\#/]m4_defn([gl_HEADER_NAME])[#{
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163 s#.*"\(.*/]m4_defn([gl_HEADER_NAME])[\)".*#\1#
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164 s#^/[^/]#//&#
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165 p
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166 q
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167 }'`'"'])
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168 else
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169 AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
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170 fi
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171 AS_VAR_POPDEF([gl_header_exists])])
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172 fi
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173 AC_SUBST(
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174 AS_TR_CPP([NEXT_]m4_defn([gl_HEADER_NAME])),
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175 [AS_VAR_GET([gl_next_header])])
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176 if test $gl_cv_have_include_next = yes || test $gl_cv_have_include_next = buggy; then
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177 # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include_next'
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178 gl_next_as_first_directive='<'gl_HEADER_NAME'>'
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179 else
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180 # INCLUDE_NEXT_AS_FIRST_DIRECTIVE='include'
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181 gl_next_as_first_directive=AS_VAR_GET([gl_next_header])
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182 fi
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183 AC_SUBST(
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184 AS_TR_CPP([NEXT_AS_FIRST_DIRECTIVE_]m4_defn([gl_HEADER_NAME])),
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185 [$gl_next_as_first_directive])
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186 AS_VAR_POPDEF([gl_next_header])])
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187 ])
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