--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2011-06-08  Bruno Haible  <bruno@clisp.org>
+
+	strerror_r-posix: Tweaks.
+	* m4/strerror.m4 (gl_FUNC_STRERROR): Omit the code that tests
+	gl_cv_func_strerror_r_works if gl_FUNC_STRERROR_R_WORKS is not present.
+	* m4/strerror_r.m4 (gl_FUNC_STRERROR_R_WORKS): Fix AC_CACHE_CHECK
+	message. Move gl_HEADER_STRING_H_DEFAULTS invocation from here...
+	(gl_FUNC_STRERROR_R): ... to here.
+	(gl_PREREQ_STRERROR_R): Test for __xpg_strerror_r.
+
 2011-06-07  Eric Blake  <eblake@redhat.com>
 
 	perror: document fixed bugs

--- a/m4/strerror.m4
+++ b/m4/strerror.m4
@@ -35,10 +35,13 @@
       dnl integers. Replace it.
       REPLACE_STRERROR=1
     fi
-    dnl If the system's strerror_r clobbers strerror, we must replace strerror.
-    case $gl_cv_func_strerror_r_works in
-      *no) REPLACE_STRERROR=1 ;;
-    esac
+    m4_ifdef([gl_FUNC_STRERROR_R_WORKS], [
+      dnl If the system's strerror_r or __xpg_strerror_r clobbers strerror's
+      dnl buffer, we must replace strerror.
+      case "$gl_cv_func_strerror_r_works" in
+        *no) REPLACE_STRERROR=1 ;;
+      esac
+    ])
   else
     dnl The system's strerror() cannot know about the new errno values we add
     dnl to <errno.h>. Replace it.

--- a/m4/strerror_r.m4
+++ b/m4/strerror_r.m4
@@ -6,6 +6,7 @@
 
 AC_DEFUN([gl_FUNC_STRERROR_R],
 [
+  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_STRERROR_R_WORKS])
 
   dnl Persuade Solaris <string.h> to declare strerror_r().
@@ -26,7 +27,7 @@
           *no) REPLACE_STRERROR_R=1 ;;
         esac
       else
-        dnl The system's strerror() has a wrong signature. Replace it.
+        dnl The system's strerror_r() has a wrong signature. Replace it.
         REPLACE_STRERROR_R=1
       fi
     else
@@ -39,15 +40,15 @@
 
 # Prerequisites of lib/strerror_r.c.
 AC_DEFUN([gl_PREREQ_STRERROR_R], [
+  dnl glibc >= 2.3.4 and cygwin 1.7.9 have a function __xpg_strerror_r.
+  AC_CHECK_FUNCS([__xpg_strerror_r])
   AC_CHECK_FUNCS_ONCE([catgets])
-  :
 ])
 
 # Detect if strerror_r works, but without affecting whether a replacement
 # strerror_r will be used.
 AC_DEFUN([gl_FUNC_STRERROR_R_WORKS],
 [
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
   AC_REQUIRE([gl_HEADER_ERRNO_H])
   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
 
@@ -120,10 +121,10 @@
         dnl The system's strerror() has a wrong signature.
         dnl glibc >= 2.3.4 and cygwin 1.7.9 have a function __xpg_strerror_r.
         AC_CHECK_FUNCS([__xpg_strerror_r])
-        dnl glibc < 2.14 does not populate buf on failure
-        dnl cygwin < 1.7.10 clobbers strerror
+        dnl In glibc < 2.14, __xpg_strerror_r does not populate buf on failure.
+        dnl In cygwin < 1.7.10, __xpg_strerror_r clobbers strerror's buffer.
         if test $ac_cv_func___xpg_strerror_r = yes; then
-          AC_CACHE_CHECK([whether strerror_r works],
+          AC_CACHE_CHECK([whether __xpg_strerror_r works],
             [gl_cv_func_strerror_r_works],
             [AC_RUN_IFELSE(
                [AC_LANG_PROGRAM(
@@ -147,8 +148,8 @@
                   ]])],
                [gl_cv_func_strerror_r_works=yes],
                [gl_cv_func_strerror_r_works=no],
-               [dnl guess no on all platforms that have __xpg_strerror_r,
-                dnl at least until fixed glibc and cygwin are more common
+               [dnl Guess no on all platforms that have __xpg_strerror_r,
+                dnl at least until fixed glibc and cygwin are more common.
                 gl_cv_func_strerror_r_works="guessing no"
                ])
             ])