1 files changed, 57 insertions, 0 deletions
diff --git a/libc/test/src/__support/math_extras_test.cpp b/libc/test/src/__support/math_extras_test.cpp
index e88b3e1d6b68..401e631ea4ba 100644
--- a/libc/test/src/__support/math_extras_test.cpp
+++ b/libc/test/src/__support/math_extras_test.cpp
@@ -101,4 +101,61 @@ TYPED_TEST(LlvmLibcBitTest, CountZeros, UnsignedTypesNoBigInt) {
     EXPECT_EQ(count_zeros<T>(cpp::numeric_limits<T>::max() >> i), i);
 }
 
+using UnsignedTypes = testing::TypeList<
+#if defined(__SIZEOF_INT128__)
+    __uint128_t,
+#endif
+    unsigned char, unsigned short, unsigned int, unsigned long,
+    unsigned long long>;
+
+TYPED_TEST(LlvmLibcBlockMathExtrasTest, add_overflow, UnsignedTypes) {
+  constexpr T ZERO = cpp::numeric_limits<T>::min();
+  constexpr T ONE(1);
+  constexpr T MAX = cpp::numeric_limits<T>::max();
+  constexpr T BEFORE_MAX = MAX - 1;
+
+  const struct {
+    T lhs;
+    T rhs;
+    T sum;
+    bool carry;
+  } TESTS[] = {
+      {ZERO, ONE, ONE, false},       // 0x00 + 0x01 = 0x01
+      {BEFORE_MAX, ONE, MAX, false}, // 0xFE + 0x01 = 0xFF
+      {MAX, ONE, ZERO, true},        // 0xFF + 0x01 = 0x00 (carry)
+      {MAX, MAX, BEFORE_MAX, true},  // 0xFF + 0xFF = 0xFE (carry)
+  };
+  for (auto tc : TESTS) {
+    T sum;
+    bool carry = add_overflow<T>(tc.lhs, tc.rhs, sum);
+    EXPECT_EQ(sum, tc.sum);
+    EXPECT_EQ(carry, tc.carry);
+  }
+}
+
+TYPED_TEST(LlvmLibcBlockMathExtrasTest, sub_overflow, UnsignedTypes) {
+  constexpr T ZERO = cpp::numeric_limits<T>::min();
+  constexpr T ONE(1);
+  constexpr T MAX = cpp::numeric_limits<T>::max();
+  constexpr T BEFORE_MAX = MAX - 1;
+
+  const struct {
+    T lhs;
+    T rhs;
+    T sub;
+    bool carry;
+  } TESTS[] = {
+      {ONE, ZERO, ONE, false},      // 0x01 - 0x00 = 0x01
+      {MAX, MAX, ZERO, false},      // 0xFF - 0xFF = 0x00
+      {ZERO, ONE, MAX, true},       // 0x00 - 0x01 = 0xFF (carry)
+      {BEFORE_MAX, MAX, MAX, true}, // 0xFE - 0xFF = 0xFF (carry)
+  };
+  for (auto tc : TESTS) {
+    T sub;
+    bool carry = sub_overflow<T>(tc.lhs, tc.rhs, sub);
+    EXPECT_EQ(sub, tc.sub);
+    EXPECT_EQ(carry, tc.carry);
+  }
+}
+
 } // namespace LIBC_NAMESPACE