--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m4/include_next.m4	Sun Aug 16 17:16:49 2009 +0000
@@ -0,0 +1,170 @@
+# include_next.m4 serial 10
+dnl Copyright (C) 2006-2008 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Paul Eggert and Derek Price.
+
+dnl Sets INCLUDE_NEXT and PRAGMA_SYSTEM_HEADER.
+dnl
+dnl INCLUDE_NEXT expands to 'include_next' if the compiler supports it, or to
+dnl 'include' otherwise.
+dnl
+dnl INCLUDE_NEXT_AS_FIRST_DIRECTIVE expands to 'include_next' if the compiler
+dnl supports it in the special case that it is the first include directive in
+dnl the given file, or to 'include' otherwise.
+dnl
+dnl PRAGMA_SYSTEM_HEADER can be used in files that contain #include_next,
+dnl so as to avoid GCC warnings when the gcc option -pedantic is used.
+dnl '#pragma GCC system_header' has the same effect as if the file was found
+dnl through the include search path specified with '-isystem' options (as
+dnl opposed to the search path specified with '-I' options). Namely, gcc
+dnl does not warn about some things, and on some systems (Solaris and Interix)
+dnl __STDC__ evaluates to 0 instead of to 1. The latter is an undesired side
+dnl effect; we are therefore careful to use 'defined __STDC__' or '1' instead
+dnl of plain '__STDC__'.
+
+AC_DEFUN([gl_INCLUDE_NEXT],
+[
+  AC_LANG_PREPROC_REQUIRE()
+  AC_CACHE_CHECK([whether the preprocessor supports include_next],
+    [gl_cv_have_include_next],
+    [rm -rf conftestd1a conftestd1b conftestd2
+     mkdir conftestd1a conftestd1b conftestd2
+     dnl The include of <stdio.h> is because IBM C 9.0 on AIX 6.1 supports
+     dnl include_next when used as first preprocessor directive in a file,
+     dnl but not when preceded by another include directive. Additionally,
+     dnl with this same compiler, include_next is a no-op when used in a
+     dnl header file that was included by specifying its absolute file name.
+     dnl Despite these two bugs, include_next is used in the compiler's
+     dnl <math.h>. By virtue of the second bug, we need to use include_next
+     dnl as well in this case.
+     cat <<EOF > conftestd1a/conftest.h
+#define DEFINED_IN_CONFTESTD1
+#include_next <conftest.h>
+#ifdef DEFINED_IN_CONFTESTD2
+int foo;
+#else
+#error "include_next doesn't work"
+#endif
+EOF
+     cat <<EOF > conftestd1b/conftest.h
+#define DEFINED_IN_CONFTESTD1
+#include <stdio.h>
+#include_next <conftest.h>
+#ifdef DEFINED_IN_CONFTESTD2
+int foo;
+#else
+#error "include_next doesn't work"
+#endif
+EOF
+     cat <<EOF > conftestd2/conftest.h
+#ifndef DEFINED_IN_CONFTESTD1
+#error "include_next test doesn't work"
+#endif
+#define DEFINED_IN_CONFTESTD2
+EOF
+     gl_save_CPPFLAGS="$CPPFLAGS"
+     CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1b -Iconftestd2"
+     AC_COMPILE_IFELSE([#include <conftest.h>],
+       [gl_cv_have_include_next=yes],
+       [CPPFLAGS="$gl_save_CPPFLAGS -Iconftestd1a -Iconftestd2"
+        AC_COMPILE_IFELSE([#include <conftest.h>],
+          [gl_cv_have_include_next=buggy],
+          [gl_cv_have_include_next=no])
+       ])
+     CPPFLAGS="$gl_save_CPPFLAGS"
+     rm -rf conftestd1a conftestd1b conftestd2
+    ])
+  PRAGMA_SYSTEM_HEADER=
+  if test $gl_cv_have_include_next = yes; then
+    INCLUDE_NEXT=include_next
+    INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
+    if test -n "$GCC"; then
+      PRAGMA_SYSTEM_HEADER='#pragma GCC system_header'
+    fi
+  else
+    if test $gl_cv_have_include_next = buggy; then
+      INCLUDE_NEXT=include
+      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include_next
+    else
+      INCLUDE_NEXT=include
+      INCLUDE_NEXT_AS_FIRST_DIRECTIVE=include
+    fi
+  fi
+  AC_SUBST([INCLUDE_NEXT])
+  AC_SUBST([INCLUDE_NEXT_AS_FIRST_DIRECTIVE])
+  AC_SUBST([PRAGMA_SYSTEM_HEADER])
+])
+
+# gl_CHECK_NEXT_HEADERS(HEADER1 HEADER2 ...)
+# ------------------------------------------
+# For each arg foo.h, if #include_next works, define NEXT_FOO_H to be
+# '<foo.h>'; otherwise define it to be
+# '"///usr/include/foo.h"', or whatever other absolute file name is suitable.
+# That way, a header file with the following line:
+#	#@INCLUDE_NEXT@ @NEXT_FOO_H@
+# behaves (after sed substitution) as if it contained
+#	#include_next <foo.h>
+# even if the compiler does not support include_next.
+# The three "///" are to pacify Sun C 5.8, which otherwise would say
+# "warning: #include of /usr/include/... may be non-portable".
+# Use `""', not `<>', so that the /// cannot be confused with a C99 comment.
+# Note: This macro assumes that the header file is not empty after
+# preprocessing, i.e. it does not only define preprocessor macros but also
+# provides some type/enum definitions or function/variable declarations.
+AC_DEFUN([gl_CHECK_NEXT_HEADERS],
+[
+  AC_REQUIRE([gl_INCLUDE_NEXT])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CHECK_HEADERS_ONCE([$1])
+
+  m4_foreach_w([gl_HEADER_NAME], [$1],
+    [AS_VAR_PUSHDEF([gl_next_header],
+		    [gl_cv_next_]m4_quote(m4_defn([gl_HEADER_NAME])))
+     if test $gl_cv_have_include_next = yes; then
+       AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
+     else
+       AC_CACHE_CHECK(
+	 [absolute name of <]m4_quote(m4_defn([gl_HEADER_NAME]))[>],
+	 m4_quote(m4_defn([gl_next_header])),
+	 [AS_VAR_PUSHDEF([gl_header_exists],
+			 [ac_cv_header_]m4_quote(m4_defn([gl_HEADER_NAME])))
+	  if test AS_VAR_GET(gl_header_exists) = yes; then
+	    AC_LANG_CONFTEST(
+	      [AC_LANG_SOURCE(
+		 [[#include <]]m4_dquote(m4_defn([gl_HEADER_NAME]))[[>]]
+	       )])
+	    dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
+	    dnl that contain only a #include of other header files and no
+	    dnl non-comment tokens of their own. This leads to a failure to
+	    dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
+	    dnl and others. The workaround is to force preservation of comments
+	    dnl through option -C. This ensures all necessary #line directives
+	    dnl are present. GCC supports option -C as well.
+	    case "$host_os" in
+	      aix*) gl_absname_cpp="$ac_cpp -C" ;;
+	      *)    gl_absname_cpp="$ac_cpp" ;;
+	    esac
+	    dnl eval is necessary to expand gl_absname_cpp.
+	    dnl Ultrix and Pyramid sh refuse to redirect output of eval,
+	    dnl so use subshell.
+	    AS_VAR_SET([gl_next_header],
+	      ['"'`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
+	       sed -n '\#/]m4_quote(m4_defn([gl_HEADER_NAME]))[#{
+		 s#.*"\(.*/]m4_quote(m4_defn([gl_HEADER_NAME]))[\)".*#\1#
+		 s#^/[^/]#//&#
+		 p
+		 q
+	       }'`'"'])
+	  else
+	    AS_VAR_SET([gl_next_header], ['<'gl_HEADER_NAME'>'])
+	  fi
+	  AS_VAR_POPDEF([gl_header_exists])])
+     fi
+     AC_SUBST(
+       AS_TR_CPP([NEXT_]m4_quote(m4_defn([gl_HEADER_NAME]))),
+       [AS_VAR_GET([gl_next_header])])
+     AS_VAR_POPDEF([gl_next_header])])
+])