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-rw-r--r--src/test/fuzz/addition_overflow.cpp17
-rw-r--r--src/test/util_tests.cpp16
-rw-r--r--src/util/overflow.h20
3 files changed, 48 insertions, 5 deletions
diff --git a/src/test/fuzz/addition_overflow.cpp b/src/test/fuzz/addition_overflow.cpp
index cfad41659e..372c1a370e 100644
--- a/src/test/fuzz/addition_overflow.cpp
+++ b/src/test/fuzz/addition_overflow.cpp
@@ -26,6 +26,12 @@ void TestAdditionOverflow(FuzzedDataProvider& fuzzed_data_provider)
const T i = fuzzed_data_provider.ConsumeIntegral<T>();
const T j = fuzzed_data_provider.ConsumeIntegral<T>();
const bool is_addition_overflow_custom = AdditionOverflow(i, j);
+ const auto maybe_add{CheckedAdd(i, j)};
+ const auto sat_add{SaturatingAdd(i, j)};
+ assert(is_addition_overflow_custom == !maybe_add.has_value());
+ assert(is_addition_overflow_custom == AdditionOverflow(j, i));
+ assert(maybe_add == CheckedAdd(j, i));
+ assert(sat_add == SaturatingAdd(j, i));
#if defined(HAVE_BUILTIN_ADD_OVERFLOW)
T result_builtin;
const bool is_addition_overflow_builtin = __builtin_add_overflow(i, j, &result_builtin);
@@ -33,11 +39,14 @@ void TestAdditionOverflow(FuzzedDataProvider& fuzzed_data_provider)
if (!is_addition_overflow_custom) {
assert(i + j == result_builtin);
}
-#else
- if (!is_addition_overflow_custom) {
- (void)(i + j);
- }
#endif
+ if (is_addition_overflow_custom) {
+ assert(sat_add == std::numeric_limits<T>::min() || sat_add == std::numeric_limits<T>::max());
+ } else {
+ const auto add{i + j};
+ assert(add == maybe_add.value());
+ assert(add == sat_add);
+ }
}
} // namespace
diff --git a/src/test/util_tests.cpp b/src/test/util_tests.cpp
index 52b24327ec..22ce9b0582 100644
--- a/src/test/util_tests.cpp
+++ b/src/test/util_tests.cpp
@@ -1474,9 +1474,17 @@ static void TestAddMatrixOverflow()
constexpr T MAXI{std::numeric_limits<T>::max()};
BOOST_CHECK(!CheckedAdd(T{1}, MAXI));
BOOST_CHECK(!CheckedAdd(MAXI, MAXI));
+ BOOST_CHECK_EQUAL(MAXI, SaturatingAdd(T{1}, MAXI));
+ BOOST_CHECK_EQUAL(MAXI, SaturatingAdd(MAXI, MAXI));
+
BOOST_CHECK_EQUAL(0, CheckedAdd(T{0}, T{0}).value());
BOOST_CHECK_EQUAL(MAXI, CheckedAdd(T{0}, MAXI).value());
BOOST_CHECK_EQUAL(MAXI, CheckedAdd(T{1}, MAXI - 1).value());
+ BOOST_CHECK_EQUAL(MAXI - 1, CheckedAdd(T{1}, MAXI - 2).value());
+ BOOST_CHECK_EQUAL(0, SaturatingAdd(T{0}, T{0}));
+ BOOST_CHECK_EQUAL(MAXI, SaturatingAdd(T{0}, MAXI));
+ BOOST_CHECK_EQUAL(MAXI, SaturatingAdd(T{1}, MAXI - 1));
+ BOOST_CHECK_EQUAL(MAXI - 1, SaturatingAdd(T{1}, MAXI - 2));
}
/* Check for overflow or underflow */
@@ -1488,9 +1496,17 @@ static void TestAddMatrix()
constexpr T MAXI{std::numeric_limits<T>::max()};
BOOST_CHECK(!CheckedAdd(T{-1}, MINI));
BOOST_CHECK(!CheckedAdd(MINI, MINI));
+ BOOST_CHECK_EQUAL(MINI, SaturatingAdd(T{-1}, MINI));
+ BOOST_CHECK_EQUAL(MINI, SaturatingAdd(MINI, MINI));
+
BOOST_CHECK_EQUAL(MINI, CheckedAdd(T{0}, MINI).value());
BOOST_CHECK_EQUAL(MINI, CheckedAdd(T{-1}, MINI + 1).value());
BOOST_CHECK_EQUAL(-1, CheckedAdd(MINI, MAXI).value());
+ BOOST_CHECK_EQUAL(MINI + 1, CheckedAdd(T{-1}, MINI + 2).value());
+ BOOST_CHECK_EQUAL(MINI, SaturatingAdd(T{0}, MINI));
+ BOOST_CHECK_EQUAL(MINI, SaturatingAdd(T{-1}, MINI + 1));
+ BOOST_CHECK_EQUAL(MINI + 1, SaturatingAdd(T{-1}, MINI + 2));
+ BOOST_CHECK_EQUAL(-1, SaturatingAdd(MINI, MAXI));
}
BOOST_AUTO_TEST_CASE(util_overflow)
diff --git a/src/util/overflow.h b/src/util/overflow.h
index c70a8b663e..6b7dd1e8fd 100644
--- a/src/util/overflow.h
+++ b/src/util/overflow.h
@@ -13,7 +13,7 @@ template <class T>
[[nodiscard]] bool AdditionOverflow(const T i, const T j) noexcept
{
static_assert(std::is_integral<T>::value, "Integral required.");
- if (std::numeric_limits<T>::is_signed) {
+ if constexpr (std::numeric_limits<T>::is_signed) {
return (i > 0 && j > std::numeric_limits<T>::max() - i) ||
(i < 0 && j < std::numeric_limits<T>::min() - i);
}
@@ -29,4 +29,22 @@ template <class T>
return i + j;
}
+template <class T>
+[[nodiscard]] T SaturatingAdd(const T i, const T j) noexcept
+{
+ if constexpr (std::numeric_limits<T>::is_signed) {
+ if (i > 0 && j > std::numeric_limits<T>::max() - i) {
+ return std::numeric_limits<T>::max();
+ }
+ if (i < 0 && j < std::numeric_limits<T>::min() - i) {
+ return std::numeric_limits<T>::min();
+ }
+ } else {
+ if (std::numeric_limits<T>::max() - i < j) {
+ return std::numeric_limits<T>::max();
+ }
+ }
+ return i + j;
+}
+
#endif // BITCOIN_UTIL_OVERFLOW_H