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[2001:8b0:1d0::1]) by mx.google.com with ESMTPS id tk1si816739bkb.31.2014.03.28.08.12.58 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Fri, 28 Mar 2014 08:12:59 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of pm215@archaic.org.uk designates 2001:8b0:1d0::1 as permitted sender) client-ip=2001:8b0:1d0::1; Received: from pm215 by mnementh.archaic.org.uk with local (Exim 4.80) (envelope-from ) id 1WTYSn-0000X7-VA; Fri, 28 Mar 2014 15:12:57 +0000 From: Peter Maydell To: qemu-devel@nongnu.org Cc: patches@linaro.org, qemu-trivial@nongnu.org Subject: [PATCH 3/3] xbzrle.c: Avoid undefined behaviour with signed arithmetic Date: Fri, 28 Mar 2014 15:12:57 +0000 Message-Id: <1396019577-2013-4-git-send-email-peter.maydell@linaro.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1396019577-2013-1-git-send-email-peter.maydell@linaro.org> References: <1396019577-2013-1-git-send-email-peter.maydell@linaro.org> X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: peter.maydell@linaro.org X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 209.85.220.172 is neither permitted nor denied by best guess record for domain of patch+caf_=patchwork-forward=linaro.org@linaro.org) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Precedence: list Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org List-ID: X-Google-Group-Id: 836684582541 List-Post: , List-Help: , List-Archive: List-Unsubscribe: , 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 --- xbzrle.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/xbzrle.c b/xbzrle.c index fbcb35d..8e220bf 100644 --- a/xbzrle.c +++ b/xbzrle.c @@ -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]) {