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[PULL,06/11] int128.h: Avoid undefined behaviours involving signed arithmetic

Message ID 1396940651-10513-7-git-send-email-mjt@msgid.tls.msk.ru
State Accepted
Commit 423d00c857ebc814ef6b5fc63f1d6c595cdc005d
Headers show

Commit Message

Michael Tokarev April 8, 2014, 7:04 a.m. UTC 
From: Peter Maydell <peter.maydell@linaro.org>

Add casts when we're performing arithmetic on the .hi parts of an
Int128, to avoid undefined behaviour.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
---
 include/qemu/int128.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/include/qemu/int128.h b/include/qemu/int128.h
index 9ed47aa..f597031 100644
--- a/include/qemu/int128.h
+++ b/include/qemu/int128.h
@@ -53,7 +53,7 @@  static inline Int128 int128_rshift(Int128 a, int n)
     if (n >= 64) {
         return (Int128) { h, h >> 63 };
     } else {
-        return (Int128) { (a.lo >> n) | (a.hi << (64 - n)), h };
+        return (Int128) { (a.lo >> n) | ((uint64_t)a.hi << (64 - n)), h };
     }
 }
 
@@ -78,7 +78,7 @@  static inline Int128 int128_neg(Int128 a)
 
 static inline Int128 int128_sub(Int128 a, Int128 b)
 {
-    return (Int128){ a.lo - b.lo, a.hi - b.hi - (a.lo < b.lo) };
+    return (Int128){ a.lo - b.lo, (uint64_t)a.hi - b.hi - (a.lo < b.lo) };
 }
 
 static inline bool int128_nonneg(Int128 a)