The tail end of x_sub implicitly assumed that an unsigned short

contains 16 bits.  Not true on Cray J90.

diff --git a/Objects/longobject.c b/Objects/longobject.c
index df69a6da67ac980d8e91c439da6139ee301f8a52..a28dbaf34d7f8c8255ab17029b386bc932c24333 100644 (file)
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -1048,6 +1048,7 @@ x_sub(PyLongObject *a, PyLongObject *b)
                borrow = a->ob_digit[i] - borrow;
                z->ob_digit[i] = borrow & MASK;
                borrow >>= SHIFT;
+               borrow &= 1; /* Keep only one sign bit */
        }
        assert(borrow == 0);
        if (sign < 0)