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      1 # environ.m4 serial 6
      2 dnl Copyright (C) 2001-2004, 2006-2012 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.
      6 
      7 AC_DEFUN_ONCE([gl_ENVIRON],
      8 [
      9   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
     10   dnl Persuade glibc <unistd.h> to declare environ.
     11   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
     12 
     13   AC_CHECK_HEADERS_ONCE([unistd.h])
     14   gt_CHECK_VAR_DECL(
     15     [#if HAVE_UNISTD_H
     16      #include <unistd.h>
     17      #endif
     18      /* mingw, BeOS, Haiku declare environ in <stdlib.h>, not in <unistd.h>.  */
     19      #include <stdlib.h>
     20     ],
     21     [environ])
     22   if test $gt_cv_var_environ_declaration != yes; then
     23     HAVE_DECL_ENVIRON=0
     24   fi
     25 ])
     26 
     27 # Check if a variable is properly declared.
     28 # gt_CHECK_VAR_DECL(includes,variable)
     29 AC_DEFUN([gt_CHECK_VAR_DECL],
     30 [
     31   define([gt_cv_var], [gt_cv_var_]$2[_declaration])
     32   AC_MSG_CHECKING([if $2 is properly declared])
     33   AC_CACHE_VAL([gt_cv_var], [
     34     AC_COMPILE_IFELSE(
     35       [AC_LANG_PROGRAM(
     36          [[$1
     37            extern struct { int foo; } $2;]],
     38          [[$2.foo = 1;]])],
     39       [gt_cv_var=no],
     40       [gt_cv_var=yes])])
     41   AC_MSG_RESULT([$gt_cv_var])
     42   if test $gt_cv_var = yes; then
     43     AC_DEFINE([HAVE_]m4_translit($2, [a-z], [A-Z])[_DECL], 1,
     44               [Define if you have the declaration of $2.])
     45   fi
     46   undefine([gt_cv_var])
     47 ])
     48