2006-05-22  Stepan Kasal  <address@hidden>
	and Ralf Wildenhues  <address@hidden>

	* lib/autoconf/lang.m4 (_AC_COMPILER_EXEEXT_DEFAULT): Drop the
	initialization of `ac_cv_exeext', do not override it if it was
	already set.  Add comment about this potential backward
	incompatibility.  Do not export `ac_cv_exeext', Libtool hasn't
	needed this for years.
	(_AC_COMPILER_EXEEXT_DEFAULT): Likewise, do not export it.
	(_AC_COMPILER_EXEEXT_WORKS, _AC_COMPILER_EXEEXT_CROSS): Typos.
	* doc/autoconf.texi (Compilers and Preprocessors) <EXEEXT>:
	Document that this test may be overridden by setting
	`ac_cv_exeext'.


--- lib/autoconf/lang.m4	2006-05-22 18:35:15.000000000 +0200
+++ lib/autoconf/lang.m4	2006-05-22 18:43:36.000000000 +0200
@@ -495,9 +495,12 @@
 rm -f $ac_rmfiles
 
 AS_IF([AC_TRY_EVAL(ac_link_default)],
-[# Be careful to initialize this variable, since it used to be cached.
-# Otherwise an old cache value of `no' led to `EXEEXT = no' in a Makefile.
-ac_cv_exeext=
+[# At one point in the past, the ac_cv_exeext variable could contain
+# the value `no'.  This would lead to `EXEEXT = no' in a Makefile.
+# If you still have a cache file around with this value, please remove
+# the setting.  Because we should not override ac_cv_exeext if it
+# was cached, so that the user can short-circuit this test for
+# compilers unknown to Autoconf.
 for ac_file in $ac_files
 do
   test -f "$ac_file" || continue
@@ -509,11 +512,13 @@
 	# certainly right.
 	break;;
     *.* )
-	ac_cv_exeext=`expr "$ac_file" : ['[^.]*\(\..*\)']`
-	# FIXME: I believe we export ac_cv_exeext for Libtool,
-	# but it would be cool to find out if it's true.  Does anybody
-	# maintain Libtool? --akim.
-	export ac_cv_exeext
+	test "${ac_cv_exeext+set}" = set ||
+	   ac_cv_exeext=`expr "$ac_file" : ['[^.]*\(\..*\)']`
+	# We set ac_cv_exeext here because the later test for it is not
+	# safe: cross compilers may not add the suffix if given an `-o'
+	# argument, so we may need to know it at that point already.
+	# Even if this section looks crufty: it has the advantage of
+	# actually working.
 	break;;
     * )
 	break;;
@@ -529,7 +534,7 @@
 # _AC_COMPILER_EXEEXT_WORKS
 # -------------------------
 m4_define([_AC_COMPILER_EXEEXT_WORKS],
-[# Check the compiler produces executables we can run.  If not, either
+[# Check that the compiler produces executables we can run.  If not, either
 # the compiler is broken, or we cross compile.
 AC_MSG_CHECKING([whether the _AC_LANG compiler works])
 # FIXME: These cross compiler hacks should be removed for Autoconf 3.0
@@ -553,7 +558,7 @@
 # _AC_COMPILER_EXEEXT_CROSS
 # -------------------------
 m4_define([_AC_COMPILER_EXEEXT_CROSS],
-[# Check the compiler produces executables we can run.  If not, either
+[# Check that the compiler produces executables we can run.  If not, either
 # the compiler is broken, or we cross compile.
 AC_MSG_CHECKING([whether we are cross compiling])
 AC_MSG_RESULT([$cross_compiling])
@@ -576,7 +581,6 @@
   case $ac_file in
     _AC_COMPILER_EXEEXT_REJECT ) ;;
     *.* ) ac_cv_exeext=`expr "$ac_file" : ['[^.]*\(\..*\)']`
-	  export ac_cv_exeext
 	  break;;
     * ) break;;
   esac
Index: doc/autoconf.texi
===================================================================
RCS file: /cvsroot/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.1021
diff -u -r1.1021 autoconf.texi
--- doc/autoconf.texi	22 May 2006 17:27:50 -0000	1.1021
+++ doc/autoconf.texi	22 May 2006 18:41:58 -0000
@@ -5911,7 +5911,9 @@
 All the tests for compilers (@code{AC_PROG_CC}, @code{AC_PROG_CXX},
 @code{AC_PROG_F77}) define the output variable @code{EXEEXT} based on
 the output of the compiler, typically to the empty string if
-Posix and @samp{.exe} if a @acronym{DOS} variant.
+Posix and @samp{.exe} if a @acronym{DOS} variant.  It can be overridden
+by passing the argument @address@hidden to
address@hidden
 
 @ovindex OBJEXT
 They also define the output variable @code{OBJEXT} based on the