Doc tweak.

[gnulib.git] / m4 / absolute-header.m4

diff --git a/m4/absolute-header.m4 b/m4/absolute-header.m4
index 6cf5c15..99f15ec 100644 (file)
--- a/m4/absolute-header.m4
+++ b/m4/absolute-header.m4
@@ -1,5 +1,5 @@
-# absolute-header.m4 serial 4
-dnl Copyright (C) 2006 Free Software Foundation, Inc.
+# absolute-header.m4 serial 9
+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.
@@ -10,14 +10,18 @@ dnl From Derek Price.
 # ---------------------------------------
 # Find the absolute name of a header file, assuming 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
+# 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>').
+# (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_LANG_PREPROC_REQUIRE()dnl
-AC_FOREACH([gl_HEADER_NAME], [$1],
+m4_foreach_w([gl_HEADER_NAME], [$1],
   [AS_VAR_PUSHDEF([gl_absolute_header],
                   [gl_cv_absolute_]m4_quote(m4_defn([gl_HEADER_NAME])))dnl
   AC_CACHE_CHECK([absolute name of <]m4_quote(m4_defn([gl_HEADER_NAME]))[>],
@@ -31,12 +35,17 @@ dnl eval is necessary to expand ac_cpp.
 dnl Ultrix and Pyramid sh refuse to redirect output of eval, so use subshell.
       AS_VAR_SET(gl_absolute_header,
 [`(eval "$ac_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;}'`])
+sed -n '\#/]m4_quote(m4_defn([gl_HEADER_NAME]))[#{
+       s#.*"\(.*/]m4_quote(m4_defn([gl_HEADER_NAME]))[\)".*#\1#
+       s#^/[^/]#//&#
+       p
+       q
+}'`])
     fi
     AS_VAR_POPDEF([ac_header_exists])dnl
     ])dnl
   AC_DEFINE_UNQUOTED(AS_TR_CPP([ABSOLUTE_]m4_quote(m4_defn([gl_HEADER_NAME]))),
-                     [<AS_VAR_GET(gl_absolute_header)>],
+                     ["AS_VAR_GET(gl_absolute_header)"],
                      [Define this to an absolute name of <]m4_quote(m4_defn([gl_HEADER_NAME]))[>.])
   AS_VAR_POPDEF([gl_absolute_header])dnl
 ])dnl