starkware-libs
diff --git a/‎corelib/src/integer.cairo‎
Lines changed: 18 additions & 6 deletions b/‎corelib/src/integer.cairo‎
Lines changed: 18 additions & 6 deletions
diff --git a/‎corelib/src/test/integer_test.cairo‎
Lines changed: 14 additions & 3 deletions b/‎corelib/src/test/integer_test.cairo‎
Lines changed: 14 additions & 3 deletions
@@ -2360,13 +2360,25 @@ impl I128Mul of Mul<i128> {
             Ok(lt0) => (upcast(bounded_int::NegateHelper::negate(lt0)), !lhs_neg),
             Err(ge0) => (upcast(ge0), lhs_neg),
         };
-        let res_as_u128 = lhs_u127 * rhs_u127;
-        let res_as_felt252: felt252 = if res_neg {
-            -res_as_u128.into()
+        let (res_high, res_as_u128) = u128_wide_mul(lhs_u127, rhs_u127);
+        if res_high != 0 {
+            crate::panic_with_felt252('i128_mul Overflow');
+        }
+        if res_neg {
+            match downcast::<
+                _, bounded_int::BoundedInt<0, 0x80000000000000000000000000000000>,
+            >(res_as_u128) {
+                Some(magnitude) => upcast(bounded_int::NegateHelper::negate(magnitude)),
+                None => crate::panic_with_felt252('i128_mul Overflow'),
+            }
         } else {
-            res_as_u128.into()
-        };
-        res_as_felt252.try_into().expect('i128_mul Overflow')
+            match downcast::<
+                _, bounded_int::BoundedInt<0, 0x7fffffffffffffffffffffffffffffff>,
+            >(res_as_u128) {
+                Some(magnitude) => upcast(magnitude),
+                None => crate::panic_with_felt252('i128_mul Overflow'),
+            }
+        }
     }
 }
 
 
@@ -1763,6 +1763,11 @@ fn test_i128_operators() {
         @-0x80000000000000000000000000000000_i128,
         'failed MIN_I128 as mul result',
     );
+    assert_eq(
+        @(1_i128 * 0x7fffffffffffffffffffffffffffffff_i128),
+        @0x7fffffffffffffffffffffffffffffff_i128,
+        'failed MAX_I128 as mul result',
+    );
     assert_lt(1_i128, 4_i128, '1 < 4');
     assert_le(1_i128, 4_i128, '1 <= 4');
     assert(!(4_i128 < 4_i128), '!(4 < 4)');
@@ -1829,23 +1834,29 @@ fn test_i128_add_underflow() {
 }
 
 #[test]
-#[should_panic]
+#[should_panic(expected: ('i128_mul Overflow',))]
 fn test_i128_mul_overflow_1() {
     0x10000000000000000000000000000000_i128 * 0x10000000000000000000000000000000_i128;
 }
 
 #[test]
-#[should_panic]
+#[should_panic(expected: ('i128_mul Overflow',))]
 fn test_i128_mul_overflow_2() {
     0x11000000000000000000000000000000_i128 * 0x10000000000000000000000000000000_i128;
 }
 
 #[test]
-#[should_panic]
+#[should_panic(expected: ('i128_mul Overflow',))]
 fn test_i128_mul_overflow_3() {
     2_i128 * 0x40000000000000000000000000000000_i128;
 }
 
+#[test]
+#[should_panic(expected: ('i128_mul Overflow',))]
+fn test_i128_mul_overflow_min_times_minus_one() {
+    -0x80000000000000000000000000000000_i128 * -1_i128;
+}
+
 #[test]
 #[should_panic(expected: 'attempt to divide with overflow')]
 fn test_i128_divmod_overflow() {