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/Misc/NEWS b/Misc/NEWS
index 84f0cf6..3b9dba0 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
Core and builtins
-----------------
+- Overflow checking code in integer division ran afoul of new gcc
+ optimizations. Changed to be more standard-conforming.
+
- Patch #1541585: fix buffer overrun when performing repr() on
a unicode string in a build with wide unicode (UCS-4) support.
@@ -127,7 +130,7 @@
- The __repr__ method of a NULL ctypes.py_object() no longer raises
an exception.
-- uuid.UUID now has a bytes_le attribute. This returns the UUID in
+- uuid.UUID now has a bytes_le attribute. This returns the UUID in
little-endian byte order for Windows. In addition, uuid.py gained some
workarounds for clocks with low resolution, to stop the code yielding
duplicate UUIDs.
@@ -286,7 +289,7 @@
- Bug #1002398: The documentation for os.path.sameopenfile now correctly
refers to file descriptors, not file objects.
-- The renaming of the xml package to xmlcore, and the import hackery done
+- The renaming of the xml package to xmlcore, and the import hackery done
to make it appear at both names, has been removed. Bug #1511497,
#1513611, and probably others.
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;