show errno on FiberError ref ruby#8711

nurse · nurse · commit 37c05ec3ed1e · 2013-07-31T08:59:25.000Z
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42270 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
diff --git a/cont.c b/cont.c
@@ -568,9 +568,10 @@ fiber_machine_stack_alloc(size_t size)
 	void *page;
 	STACK_GROW_DIR_DETECTION;
 
+	errno = 0;
 	ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, FIBER_STACK_FLAGS, -1, 0);
 	if (ptr == MAP_FAILED) {
-	    rb_raise(rb_eFiberError, "can't alloc machine stack to fiber");
+	    rb_raise(rb_eFiberError, "can't alloc machine stack to fiber errno: %d", errno);
 	}
 
 	/* guard page setup */
