_PyLong_AsByteArray: Don't do the "delicate overflow" check unless it's
truly needed; usually saves a little time, but no change in semantics.
diff --git a/Objects/longobject.c b/Objects/longobject.c
index f8a9129..44819701 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -424,18 +424,27 @@
*p = (unsigned char)(accum & 0xff);
p += pincr;
}
-
- /* Fill remaining bytes with copies of the sign bit. */
- for ( ; j < n; ++j, p += pincr)
- *p = (unsigned char)(do_twos_comp ? 0xff : 0);
-
- /* Check for delicate overflow (not enough room for the sign bit). */
- if (j > 0 && is_signed) {
+ else if (j == n && n > 0 && is_signed) {
+ /* The main loop filled the byte array exactly, so the code
+ just above didn't get to ensure there's a sign bit, and the
+ loop below wouldn't add one either. Make sure a sign bit
+ exists. */
unsigned char msb = *(p - pincr);
- int sign_bit_set = (msb & 0x80) != 0;
- if (sign_bit_set != do_twos_comp)
+ int sign_bit_set = msb >= 0x80;
+ assert(accumbits == 0);
+ if (sign_bit_set == do_twos_comp)
+ return 0;
+ else
goto Overflow;
}
+
+ /* Fill remaining bytes with copies of the sign bit. */
+ {
+ unsigned char signbyte = do_twos_comp ? 0xffU : 0U;
+ for ( ; j < n; ++j, p += pincr)
+ *p = signbyte;
+ }
+
return 0;
Overflow: