Avoid signed overflow in MSVC AMR64 secp256k1_mul128

sipa · sipa · commit 3afce0af7c00 · 2022-11-17T09:44:10.000-05:00
diff --git a/src/int128_struct_impl.h b/src/int128_struct_impl.h
@@ -19,7 +19,7 @@ static SECP256K1_INLINE uint64_t secp256k1_umul128(uint64_t a, uint64_t b, uint6
 
 static SECP256K1_INLINE int64_t secp256k1_mul128(int64_t a, int64_t b, int64_t* hi) {
     *hi = __mulh(a, b);
-    return a * b;
+    return (uint64_t)a * (uint64_t)b;
 }
 #    else
 /* On x84_64 MSVC, use native _(u)mul128 for 64x64->128 multiplications. */

Original file line number	Diff line number	Diff line change
`@@ -19,7 +19,7 @@ static SECP256K1_INLINE uint64_t secp256k1_umul128(uint64_t a, uint64_t b, uint6`
`19`	`19`
`20`	`20`	`static SECP256K1_INLINE int64_t secp256k1_mul128(int64_t a, int64_t b, int64_t* hi) {`
`21`	`21`	`*hi = __mulh(a, b);`
`22`		`- return a * b;`
	`22`	`+ return (uint64_t)a * (uint64_t)b;`
`23`	`23`	`}`
`24`	`24`	`# else`
`25`	`25`	`/* On x84_64 MSVC, use native _(u)mul128 for 64x64->128 multiplications. */`