Make pthread_attr_getstack fail with EINVAL when called in "unspecified behavior" situation wherein the stackaddr was never set.

nptl/ChangeLog

@@ -1,3 +1,8 @@
+2013-04-19  Roland McGrath  <roland@hack.frob.com>
+
+	* pthread_attr_getstack.c: Fail with EINVAL if the stack address has
+	not been set.
+
 2013-04-11  Andreas Schwab  <schwab@suse.de>
 
 	* sysdeps/unix/sysv/linux/i386/i486/pthread_cond_timedwait.S

nptl/pthread_attr_getstack.c

@@ -31,6 +31,9 @@ __pthread_attr_getstack (attr, stackaddr, stacksize)
   assert (sizeof (*attr) >= sizeof (struct pthread_attr));
   iattr = (struct pthread_attr *) attr;
 
+  if (!(iattr->flags & ATTR_FLAG_STACKADDR))
+    return EINVAL;
+
   /* Store the result.  */
   *stackaddr = (char *) iattr->stackaddr - iattr->stacksize;
   *stacksize = iattr->stacksize;