[Help-smalltalk] [PATCH 1/1] ZeroDivide bug in float printing

[Derek Zhou]

To fix 64bit mode integer multiply overflow detection.
This method should be more robust wrt. compiler optimization

diff --git a/libgst/interp.inl b/libgst/interp.inl
index dbc631b..3583b19 100644
--- a/libgst/interp.inl
+++ b/libgst/interp.inl
@@ -199,15 +199,23 @@ mul_with_check (OOP op1, OOP op2, mst_Boolean *overflow)
   /* This fallback method uses a division to do overflow check */
   else
     {
-      if COMMON ((((uintptr_t) (a | b)) < (1L << (ST_INT_SIZE / 2))
-                 || b == 0
-                 || result / b == a)
-                 && !INT_OVERFLOW (result))
-        return FROM_INT (result);
-      else
-        *overflow = true;
+      intptr_t abs_a = ABS (a);
+      intptr_t abs_b = ABS (b);
+      intptr_t limit = (1L << (ST_INT_SIZE / 2 - 1));
+      if (COMMON ( abs_a < limit && abs_b < limit ))
+       goto legal;
+      if (UNCOMMON (b == 0L))
+       goto legal;
+      if (UNCOMMON (INT_OVERFLOW (result)))
+       goto overflow;
+      if (UNCOMMON (MAX_ST_INT / abs_b < abs_a))
+       goto overflow;
+    legal:
+      return FROM_INT (result);
     }
 
+ overflow:
+  *overflow = true;
   return FROM_INT (0);
 #endif
 }