+
+# 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
+}'`])
+])