Merge #18393: tests: Don't assume presence of __builtin_mul_overflow(…) in MultiplicationOverflow(…) fuzzing harness

7c1ac70c01 tests: Don't assume presence of __builtin_mul_overflow in MultiplicationOverflow(...) fuzzing harness (practicalswift)

Pull request description:

  Don't assume presence of `__builtin_mul_overflow(…)` in `MultiplicationOverflow(…)` fuzzing harness.

  Fixes #18389.

ACKs for top commit:
  naumenkogs:
    ACK 7c1ac70

Tree-SHA512: b6f1040a088088ff7e4f5c038f0f710ca2b515387bac3cd249afe97613641f7f3754f61d73d7233f23b8296115fab5bbf656168624a2cb74909577440a49a359

src/test/fuzz/multiplication_overflow.cpp

@@ -10,6 +10,14 @@
 #include <string>
 #include <vector>
 
+#if defined(__has_builtin)
+#if __has_builtin(__builtin_mul_overflow)
+#define HAVE_BUILTIN_MUL_OVERFLOW
+#endif
+#elif defined(__GNUC__) && (__GNUC__ >= 5)
+#define HAVE_BUILTIN_MUL_OVERFLOW
+#endif
+
 namespace {
 template <typename T>
 void TestMultiplicationOverflow(FuzzedDataProvider& fuzzed_data_provider)
@@ -17,12 +25,18 @@ void TestMultiplicationOverflow(FuzzedDataProvider& fuzzed_data_provider)
     const T i = fuzzed_data_provider.ConsumeIntegral<T>();
     const T j = fuzzed_data_provider.ConsumeIntegral<T>();
     const bool is_multiplication_overflow_custom = MultiplicationOverflow(i, j);
+#if defined(HAVE_BUILTIN_MUL_OVERFLOW)
     T result_builtin;
     const bool is_multiplication_overflow_builtin = __builtin_mul_overflow(i, j, &result_builtin);
     assert(is_multiplication_overflow_custom == is_multiplication_overflow_builtin);
     if (!is_multiplication_overflow_custom) {
         assert(i * j == result_builtin);
     }
+#else
+    if (!is_multiplication_overflow_custom) {
+        (void)(i * j);
+    }
+#endif
 }
 } // namespace
 
@@ -38,5 +52,4 @@ void test_one_input(const std::vector<uint8_t>& buffer)
     TestMultiplicationOverflow<char>(fuzzed_data_provider);
     TestMultiplicationOverflow<unsigned char>(fuzzed_data_provider);
     TestMultiplicationOverflow<signed char>(fuzzed_data_provider);
-    TestMultiplicationOverflow<bool>(fuzzed_data_provider);
 }