i_divmod(): As discussed on Python-Dev, changed the overflow
checking to live happily with recent gcc optimizations that
assume signed integer arithmetic never overflows.
diff --git a/Objects/intobject.c b/Objects/intobject.c
index c7137df..b94e3e9 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -564,8 +564,14 @@
"integer division or modulo by zero");
return DIVMOD_ERROR;
}
- /* (-sys.maxint-1)/-1 is the only overflow case. */
- if (y == -1 && x < 0 && x == -x)
+ /* (-sys.maxint-1)/-1 is the only overflow case. x is the most
+ * negative long iff x < 0 and, on a 2's-complement box, x == -x.
+ * However, -x is undefined (by C) if x /is/ the most negative long
+ * (it's a signed overflow case), and some compilers care. So we cast
+ * x to unsigned long first. However, then other compilers warn about
+ * applying unary minus to an unsigned operand. Hence the weird "0-".
+ */
+ if (y == -1 && x < 0 && (unsigned long)x == 0-(unsigned long)x)
return DIVMOD_OVERFLOW;
xdivy = x / y;
xmody = x - xdivy * y;