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diff --git a/m4/absolute-header.m4 b/m4/absolute-header.m4
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+# absolute-header.m4 serial 12
+dnl Copyright (C) 2006-2010 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 Derek Price.
+
+# gl_ABSOLUTE_HEADER(HEADER1 HEADER2 ...)
+# ---------------------------------------
+# Find the absolute name of a header file, testing first if the header exists.
+# If the header were sys/inttypes.h, this macro would define
+# ABSOLUTE_SYS_INTTYPES_H to the `""' quoted absolute name of sys/inttypes.h
+# in config.h
+# (e.g. `#define ABSOLUTE_SYS_INTTYPES_H "///usr/include/sys/inttypes.h"').
+# 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_ABSOLUTE_HEADER],
+[AC_REQUIRE([AC_CANONICAL_HOST])
+AC_LANG_PREPROC_REQUIRE()dnl
+m4_foreach_w([gl_HEADER_NAME], [$1],
+ [AS_VAR_PUSHDEF([gl_absolute_header],
+ [gl_cv_absolute_]m4_defn([gl_HEADER_NAME]))dnl
+ AC_CACHE_CHECK([absolute name of <]m4_defn([gl_HEADER_NAME])[>],
+ m4_defn([gl_absolute_header]),
+ [AS_VAR_PUSHDEF([ac_header_exists],
+ [ac_cv_header_]m4_defn([gl_HEADER_NAME]))dnl
+ AC_CHECK_HEADERS_ONCE(m4_defn([gl_HEADER_NAME]))dnl
+ if test AS_VAR_GET(ac_header_exists) = yes; then
+ gl_ABSOLUTE_HEADER_ONE(m4_defn([gl_HEADER_NAME]))
+ fi
+ AS_VAR_POPDEF([ac_header_exists])dnl
+ ])dnl
+ AC_DEFINE_UNQUOTED(AS_TR_CPP([ABSOLUTE_]m4_defn([gl_HEADER_NAME])),
+ ["AS_VAR_GET(gl_absolute_header)"],
+ [Define this to an absolute name of <]m4_defn([gl_HEADER_NAME])[>.])
+ AS_VAR_POPDEF([gl_absolute_header])dnl
+])dnl
+])# gl_ABSOLUTE_HEADER
+
+# gl_ABSOLUTE_HEADER_ONE(HEADER)
+# ------------------------------
+# Like gl_ABSOLUTE_HEADER, except that:
+# - it assumes that the header exists,
+# - it uses the current CPPFLAGS,
+# - it does not cache the result,
+# - it is silent.
+AC_DEFUN([gl_ABSOLUTE_HEADER_ONE],
+[
+ AC_LANG_CONFTEST([AC_LANG_SOURCE([[#include <]]m4_dquote([$1])[[>]])])
+ dnl AIX "xlc -E" and "cc -E" omit #line directives for header files
+ dnl that contain only a #include of other header files and no
+ dnl non-comment tokens of their own. This leads to a failure to
+ dnl detect the absolute name of <dirent.h>, <signal.h>, <poll.h>
+ dnl and others. The workaround is to force preservation of comments
+ dnl through option -C. This ensures all necessary #line directives
+ dnl are present. GCC supports option -C as well.
+ case "$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_cv_absolute_]AS_TR_SH([[$1]]),
+[`(eval "$gl_absname_cpp conftest.$ac_ext") 2>&AS_MESSAGE_LOG_FD |
+sed -n '\#/$1#{
+ s#.*"\(.*/$1\)".*#\1#
+ s#^/[^/]#//&#
+ p
+ q
+}'`])
+])