--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2010-09-08  Eric Blake  <eblake@redhat.com>
 
+	unsetenv: fix OpenBSD bug
+	* m4/setenv.m4 (gl_FUNC_UNSETENV): Check for OpenBSD bug.
+	* doc/posix-functions/unsetenv.texi (unsetenv): Update
+	documentation.
+	Reported by Jim Meyering.
+
 	strtod: work around IRIX 6.5 bug
 	* lib/strtod.c (strtod): Reparse number on shorter string if
 	exponent parse was invalid.

--- a/doc/posix-functions/unsetenv.texi
+++ b/doc/posix-functions/unsetenv.texi
@@ -4,7 +4,7 @@
 
 POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/unsetenv.html}
 
-Gnulib module: setenv
+Gnulib module: unsetenv
 
 Portability problems fixed by Gnulib:
 @itemize
@@ -18,7 +18,7 @@
 @item
 On some platforms, this function does not fail with @samp{EINVAL} when
 passed an empty string or a string containing @samp{=}:
-FreeBSD 6.0, NetBSD 1.6, OpenBSD 3.8.
+FreeBSD 6.0, NetBSD 1.6, OpenBSD 4.7.
 @item
 This function removes only the first value association for the given
 environment variable, not all of them, on some platforms:

--- a/m4/setenv.m4
+++ b/m4/setenv.m4
@@ -1,4 +1,4 @@
-# setenv.m4 serial 17
+# setenv.m4 serial 18
 dnl Copyright (C) 2001-2004, 2006-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -78,10 +78,12 @@
     fi
 
     dnl Solaris 10 unsetenv does not remove all copies of a name.
-    AC_CACHE_CHECK([whether unsetenv works on duplicates],
+    dnl OpenBSD 4.7 unsetenv("") does not fail.
+    AC_CACHE_CHECK([whether unsetenv obeys POSIX],
       [gl_cv_func_unsetenv_works],
       [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
        #include <stdlib.h>
+       #include <errno.h>
       ]], [[
        char entry[] = "b=2";
        if (putenv ((char *) "a=1")) return 1;
@@ -89,6 +91,7 @@
        entry[0] = 'a';
        unsetenv ("a");
        if (getenv ("a")) return 3;
+       if (!unsetenv ("") || errno != EINVAL) return 4;
       ]])],
       [gl_cv_func_unsetenv_works=yes], [gl_cv_func_unsetenv_works=no],
       [gl_cv_func_unsetenv_works="guessing no"])])