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Introduce mixed_sign_less()/min()/max() (#18)

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Previously, there was mixed sign comparison:
```
reflected_min_v = -120 > 0U ? -120 : 0
```
which returns -120 because the condition is true, since the
compiler casts the signed value to unsigned, leading to a huge value.
This caused the following values as result:

```
reflected_min_v == -120
min_v = -1
static_cast<U>(min_v) = 18446744073709551615
```

The last one is used in magic_enum::enum_index().
This commit is contained in:
Alexander Karatarakis 2019-10-14 00:44:09 -07:00 • committed by Daniil Goncharov
parent 1f3ea64407
commit 0f36cd5b0f
2 changed files with 114 additions and 6 deletions
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84
test/test.cpp
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@ -469,3 +469,87 @@ TEST_CASE("enum_traits") {
REQUIRE(enum_traits<number>::type_name == "number");
}
}
TEST_CASE("extrema") {
enum class BadColor : uint64_t
{
RED,
GREEN,
YELLOW,
// The value NONE is ignored (out of range).
// However, it affects the value of min_v. When reflected_min_v was incorrect, the
// presence of NONE caused miv_v to be equal to -1, which was then cast to unsigned,
// leading to a value of 18446744073709551615 (numeric_limit_max of uint64_t).
NONE = std::numeric_limits<uint64_t>::max(),
};
SECTION("min") {
REQUIRE(magic_enum::enum_range<BadColor>::min == MAGIC_ENUM_RANGE_MIN);
REQUIRE(magic_enum::detail::reflected_min_v<BadColor> == 0);
REQUIRE(magic_enum::detail::min_v<BadColor> == 0);
}
SECTION("max") {
REQUIRE(magic_enum::enum_range<BadColor>::max == MAGIC_ENUM_RANGE_MAX);
REQUIRE(magic_enum::detail::reflected_max_v<BadColor> == MAGIC_ENUM_RANGE_MAX);
REQUIRE(magic_enum::detail::max_v<BadColor> == 2);
}
}
TEST_CASE("mixed_sign_less") {
using magic_enum::detail::mixed_sign_less;
constexpr uint64_t uint64_t_min = std::numeric_limits<uint64_t>::min();
constexpr uint32_t uint32_t_min = std::numeric_limits<uint32_t>::min();
constexpr uint32_t uint32_t_max = std::numeric_limits<uint32_t>::max();
constexpr uint64_t uint64_t_max = std::numeric_limits<uint64_t>::max();
constexpr int64_t int64_t_min = std::numeric_limits<int64_t>::min();
constexpr int32_t int32_t_min = std::numeric_limits<int32_t>::min();
constexpr int32_t int32_t_max = std::numeric_limits<int32_t>::max();
constexpr int64_t int64_t_max = std::numeric_limits<int64_t>::max();
// Also testing with offset to avoid corner cases
// Two variables to avoid hidden casts
constexpr int64_t offset_int64_t = 17;
constexpr int32_t offset_int32_t = 17;
SECTION("same signedness") {
REQUIRE(mixed_sign_less(-5, -3));
REQUIRE(mixed_sign_less(27U, 49U));
}
SECTION("same signedness, different width") {
REQUIRE(mixed_sign_less(uint32_t_max, uint64_t_max));
REQUIRE(!mixed_sign_less(uint64_t_max, uint32_t_max));
REQUIRE(mixed_sign_less(int64_t_min, int32_t_min));
REQUIRE(!mixed_sign_less(int32_t_min, int64_t_min));
REQUIRE(mixed_sign_less(int64_t_min + offset_int64_t, int32_t_min + offset_int32_t));
REQUIRE(!mixed_sign_less(int32_t_min + offset_int32_t, int64_t_min + offset_int64_t));
}
SECTION("left signed, right unsigned") {
REQUIRE(mixed_sign_less(-5, 3U));
REQUIRE(mixed_sign_less(3, 5U));
}
SECTION("left signed, right unsigned, different width") {
REQUIRE(mixed_sign_less(int32_t_max, uint64_t_max));
REQUIRE(!mixed_sign_less(int64_t_max, uint32_t_max));
REQUIRE(mixed_sign_less(int32_t_min, uint64_t_min));
REQUIRE(mixed_sign_less(int64_t_min, uint32_t_min));
REQUIRE(mixed_sign_less(int32_t_max - offset_int32_t, uint64_t_max));
REQUIRE(!mixed_sign_less(int64_t_max - offset_int64_t, uint32_t_max));
REQUIRE(mixed_sign_less(int32_t_min + offset_int32_t, uint64_t_min));
REQUIRE(mixed_sign_less(int64_t_min + offset_int64_t, uint32_t_min));
}
SECTION("left unsigned, right signed") {
REQUIRE(!mixed_sign_less(3U, -5));
REQUIRE(mixed_sign_less(3U, 5));
}
SECTION("left unsigned, right signed, different width") {
REQUIRE(mixed_sign_less(uint32_t_max, int64_t_max));
REQUIRE(!mixed_sign_less(uint64_t_max, int32_t_max));
REQUIRE(!mixed_sign_less(uint32_t_min, int64_t_min));
REQUIRE(!mixed_sign_less(uint64_t_min, int32_t_min));
REQUIRE(mixed_sign_less(uint32_t_max, int64_t_max - offset_int32_t));
REQUIRE(!mixed_sign_less(uint64_t_max, int32_t_max - offset_int64_t));
REQUIRE(!mixed_sign_less(uint32_t_min, int64_t_min + offset_int32_t));
REQUIRE(!mixed_sign_less(uint64_t_min, int32_t_min + offset_int64_t));
}
}