* NEWS: New macro AC_C_TYPEOF.

* doc/autoconf.texi (C Compiler): Document AC_C_TYPEOF.
* lib/autoconf/c.m4 (AC_C_TYPEOF): New macro.
* tests/c.at (C keywords): Test AC_C_TYPEOF.

ChangeLog

@@ -1,5 +1,10 @@
 2005-07-06  Paul Eggert  <eggert@cs.ucla.edu>
 
+	* NEWS: New macro AC_C_TYPEOF.
+	* doc/autoconf.texi (C Compiler): Document AC_C_TYPEOF.
+	* lib/autoconf/c.m4 (AC_C_TYPEOF): New macro.
+	* tests/c.at (C keywords): Test AC_C_TYPEOF.
+
 	Fix problems reported by Nicolas Joly.
 	* tests/base.at (Input/Output): Ignore 'loading site script' chatter.
 	* tests/local.at (AT_CONFIG_CMP): Ignore lines like "LIBS=''" too.

NEWS

@@ -32,6 +32,9 @@
   future release; the old style value, which matches (../)*, is (and will
   continue to be) available as ac_top_build_prefix.
 
+** AC_C_TYPEOF
+  New macro to check for support of 'typeof' syntax a la GNU C.
+
 ** AC_PROG_CC_C89, AC_PROG_CC_C99
   New macros for ISO C99 support.  AC_PROG_CC_C89 and AC_PROG_CC_C99
   check for ANSI C89 and ISO C99 support respectively.

doc/autoconf.texi

@@ -5949,6 +5949,16 @@ found in macros such as this:
 @end example
 @end defmac
 
+@defmac AC_C_TYPEOF
+@acindex{C_TYPEOF}
+@cvindex HAVE_TYPEOF
+@cvindex typeof
+If the C compiler supports GCC's @code{typeof} syntax, define
+@code{HAVE_TYPEOF}.  If the support is available only via a different
+spelling of the keyword (e.g., @code{__typeof__}), define @code{typeof}
+to that spelling.
+@end defmac
+
 @defmac AC_C_PROTOTYPES
 @acindex{C_PROTOTYPES}
 @cvindex PROTOTYPES

lib/autoconf/c.m4

@@ -45,6 +45,7 @@
 # to the GPL from your modified version.
 #
 # Written by David MacKenzie, with help from
+# Akim Demaille, Paul Eggert,
 # Franc,ois Pinard, Karl Berry, Richard Pixley, Ian Lance Taylor,
 # Roland McGrath, Noah Friedman, david d zuhn, and many others.
 
@@ -1433,3 +1434,43 @@ else
   AC_MSG_RESULT([no])
 fi
 ])# AC_C_PROTOTYPES
+
+
+# AC_C_TYPEOF
+# -----------
+# Check if the C compiler supports GCC's typeof syntax.
+# The test case provokes incompatibilities in the Sun C compilers
+# (both Solaris 8 and Solaris 10).
+AC_DEFUN([AC_C_TYPEOF],
+[
+  AC_CACHE_CHECK([for typeof syntax and keyword spelling], ac_cv_c_typeof,
+    [ac_cv_c_typeof=no
+     for ac_kw in typeof __typeof__ no; do
+       test $ac_kw = no && break
+       AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
+	 [[
+	   int value;
+	   return
+	     (! ((void)
+		 ((struct {
+		   char a [1
+			   + ! (($ac_kw (value))
+				(($ac_kw (value)) 0 < ($ac_kw (value)) -1
+				 ? ($ac_kw (value)) - 1
+				 : ~ (~ ($ac_kw (value)) 0
+				      << sizeof ($ac_kw (value)))))]; } *)
+		  0),
+		 0));
+	 ]])],
+	 [ac_cv_c_typeof=$ac_kw])
+       test $ac_cv_c_typeof != no && break
+     done])
+  if test $ac_cv_c_typeof != no; then
+    AC_DEFINE([HAVE_TYPEOF], 1,
+      [Define to 1 if typeof works with your compiler.])
+    if test $ac_cv_c_typeof != typeof; then
+      AC_DEFINE_UNQUOTED([typeof], [$ac_cv_c_typeof],
+	[Define to __typeof__ if your compiler spells it that way.])
+    fi
+  fi
+])

tests/c.at

@@ -74,14 +74,15 @@ AT_CLEANUP
 ## C keywords.  ##
 ## ------------ ##
 
-# GCC supports `const' and `volatile'.
+# GCC supports `const', `typeof', and `volatile'.
 AT_CHECK_MACRO([C keywords],
 [[AC_PROG_CC
 AC_C_CONST
+AC_C_TYPEOF
 AC_C_VOLATILE
-case $GCC,$ac_cv_c_const,$ac_cv_c_volatile in
+case $GCC,$ac_cv_c_const,$ac_cv_c_typeof,$ac_cv_c_volatile in
  yes,*no*)
-   AC_MSG_ERROR([failed to detect `const' or `volatile' support]);;
+   AC_MSG_ERROR([failed to detect `const', `typeof', or `volatile' support]);;
 esac
 ]])