Repair portability of sign extension when reading signed ints on boxes
where sizeof(long)==8. This *was* broken on boxes where signed right
shifts didn't sign-extend, but not elsewhere. Unfortunately, apart
from the Cray T3E I don't know of such a box, and Guido has so far
refused to buy me any Cray machines for home Python testing <wink>.
More immediately interesting would be if someone could please test
this on *any* sizeof(long)==8 box, to make sure I didn't break it.
diff --git a/Modules/structmodule.c b/Modules/structmodule.c
index a28ca54..9d1c436 100644
--- a/Modules/structmodule.c
+++ b/Modules/structmodule.c
@@ -653,11 +653,9 @@
do {
x = (x<<8) | (*p++ & 0xFF);
} while (--i > 0);
- i = 8*(sizeof(long) - f->size);
- if (i) {
- x <<= i;
- x >>= i;
- }
+ /* Extend the sign bit. */
+ if (SIZEOF_LONG > f->size)
+ x |= -(x & (1L << (8*f->size - 1)));
return PyInt_FromLong(x);
}
@@ -767,11 +765,9 @@
do {
x = (x<<8) | (p[--i] & 0xFF);
} while (i > 0);
- i = 8*(sizeof(long) - f->size);
- if (i) {
- x <<= i;
- x >>= i;
- }
+ /* Extend the sign bit. */
+ if (SIZEOF_LONG > f->size)
+ x |= -(x & (1L << (8*f->size - 1)));
return PyInt_FromLong(x);
}