Fix for SF bug #576327: zipfile when sizeof(long) == 8
binascii_crc32(): Make this return a signed 4-byte result across
platforms. The other way to make this platform-independent would be to
make it return an unsigned unbounded int, but the evidence suggests
other code out there treats it like a signed 4-byte int (e.g., existing
code writing the result with struct.pack "l" format).
Bugfix candidate.
diff --git a/Modules/binascii.c b/Modules/binascii.c
index 6cba688..66644e1 100644
--- a/Modules/binascii.c
+++ b/Modules/binascii.c
@@ -864,6 +864,7 @@
unsigned char *bin_data;
unsigned long crc = 0UL; /* initial value of CRC */
int len;
+ long result;
if ( !PyArg_ParseTuple(args, "s#|l:crc32", &bin_data, &len, &crc) )
return NULL;
@@ -872,7 +873,16 @@
while(len--)
crc = crc_32_tab[(crc ^ *bin_data++) & 0xffUL] ^ (crc >> 8);
/* Note: (crc >> 8) MUST zero fill on left */
- return Py_BuildValue("l", crc ^ 0xFFFFFFFFUL);
+
+ result = (long)(crc ^ 0xFFFFFFFFUL);
+ /* If long is > 32 bits, extend the sign bit. This is one way to
+ * ensure the result is the same across platforms. The other way
+ * would be to return an unbounded long, but the evidence suggests
+ * that lots of code outside this treats the result as if it were
+ * a signed 4-byte integer.
+ */
+ result |= -(result & (1L << 31));
+ return PyInt_FromLong(result);
}