[RFC PATCH 1/8] qemu/int128: avoid undefined behavior in int128_lshift

[matheus . ferst]

From: Matheus Ferst <matheus.ferst@eldorado.org.br>

Avoid the left shift of negative values in int128_lshift by casting
a/a.hi to unsigned.

Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
---
 include/qemu/int128.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/qemu/int128.h b/include/qemu/int128.h
index 2c4064256c..2a19558ac6 100644
--- a/include/qemu/int128.h
+++ b/include/qemu/int128.h
@@ -85,7 +85,7 @@ static inline Int128 int128_rshift(Int128 a, int n)
 
 static inline Int128 int128_lshift(Int128 a, int n)
 {
-    return a << n;
+    return (__uint128_t)a << n;
 }
 
 static inline Int128 int128_add(Int128 a, Int128 b)
@@ -305,7 +305,7 @@ static inline Int128 int128_lshift(Int128 a, int n)
     if (n >= 64) {
         return int128_make128(0, l);
     } else if (n > 0) {
-        return int128_make128(l, (a.hi << n) | (a.lo >> (64 - n)));
+        return int128_make128(l, ((uint64_t)a.hi << n) | (a.lo >> (64 - n)));
     }
     return a;
 }
-- 
2.25.1