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xbzrle.c: Avoid undefined behaviour with signed arithmetic 

Use unsigned types for doing bitwise arithmetic in the xzbrle
calculations, to avoid undefined behaviour:

 xbzrle.c:99:49: runtime error: left shift of 72340172838076673
 by 7 places cannot be represented in type 'long'

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Peter Maydell 2014-03-28 15:12:57 +00:00 committed by Michael Tokarev
parent 423d00c857
commit 968fc24d84
1 changed files with 5 additions and 3 deletions
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8
xbzrle.c
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@ -28,7 +28,7 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
{
uint32_t zrun_len = 0, nzrun_len = 0;
int d = 0, i = 0;
long res, xor;
long res;
uint8_t *nzrun_start = NULL;
g_assert(!(((uintptr_t)old_buf | (uintptr_t)new_buf | slen) %
@ -93,9 +93,11 @@ int xbzrle_encode_buffer(uint8_t *old_buf, uint8_t *new_buf, int slen,
/* word at a time for speed, use of 32-bit long okay */
if (!res) {
/* truncation to 32-bit long okay */
long mask = (long)0x0101010101010101ULL;
unsigned long mask = (unsigned long)0x0101010101010101ULL;
while (i < slen) {
xor = *(long *)(old_buf + i) ^ *(long *)(new_buf + i);
unsigned long xor;
xor = *(unsigned long *)(old_buf + i)
^ *(unsigned long *)(new_buf + i);
if ((xor - mask) & ~xor & (mask << 7)) {
/* found the end of an nzrun within the current long */
while (old_buf[i] != new_buf[i]) {