From b3d65fab9b444ed6f97685d56a1a2462e3c07359 Mon Sep 17 00:00:00 2001
From: Joel Dice <joel.dice@gmail.com>
Date: Sat, 9 Apr 2011 21:09:59 -0600
Subject: [PATCH] fix handling of interfaces in isAssignableFrom

The old version was both incorrect (in the case where both arguments
are interfaces) and inefficient.
---
 src/machine.cpp | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/src/machine.cpp b/src/machine.cpp
index bc6d1bdf63..2f7f896e2f 100644
--- a/src/machine.cpp
+++ b/src/machine.cpp
@@ -3176,13 +3176,12 @@ isAssignableFrom(Thread* t, object a, object b)
       }
     }
 
-    for (; b; b = classSuper(t, b)) {
-      object itable = classInterfaceTable(t, b);
-      if (itable) {
-        for (unsigned i = 0; i < arrayLength(t, itable); i += 2) {
-          if (arrayBody(t, itable, i) == a) {
-            return true;
-          }
+    object itable = classInterfaceTable(t, b);
+    if (itable) {
+      unsigned stride = (classFlags(t, b) & ACC_INTERFACE) ? 1 : 2;
+      for (unsigned i = 0; i < arrayLength(t, itable); i += stride) {
+        if (arrayBody(t, itable, i) == a) {
+          return true;
         }
       }
     }