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Implement P2291R3 constexpr Integral <charconv> #3049

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merged 9 commits into from
Aug 27, 2022
Merged

Implement P2291R3 constexpr Integral <charconv> #3049

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7bf72d3
Implement P2291R3
AdamBucior Aug 23, 2022
415f037
Feature-test macro
AdamBucior Aug 23, 2022
92b867e
`inline` instead of `static`
AdamBucior Aug 23, 2022
87a6cbd
Code review
AdamBucior Aug 23, 2022
4a69c4a
Casey's review comments
CaseyCarter Aug 23, 2022
a043b99
static_cast<size_t> is now unnecessary.
StephanTLavavej Aug 24, 2022
1ce8fe8
Rewrap comments.
StephanTLavavej Aug 24, 2022
53c80c5
Add const.
StephanTLavavej Aug 24, 2022
f1f5066
Use direct-initialization.
StephanTLavavej Aug 24, 2022
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83 changes: 43 additions & 40 deletions stl/inc/charconv
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Expand Up @@ -35,7 +35,7 @@ inline constexpr char _Charconv_digits[] = {'0', '1', '2', '3', '4', '5', '6', '
_STL_INTERNAL_STATIC_ASSERT(_STD size(_Charconv_digits) == 36);

template <class _RawTy>
_NODISCARD to_chars_result _Integer_to_chars(
_NODISCARD _CONSTEXPR23 to_chars_result _Integer_to_chars(
char* _First, char* const _Last, const _RawTy _Raw_value, const int _Base) noexcept {
_Adl_verify_range(_First, _Last);
_STL_ASSERT(_Base >= 2 && _Base <= 36, "invalid base in to_chars()");
Expand Down Expand Up @@ -152,52 +152,55 @@ _NODISCARD to_chars_result _Integer_to_chars(
return {_Last, errc::value_too_large};
}

_CSTD memcpy(_First, _RNext, static_cast<size_t>(_Digits_written));
_Copy_n_unchecked4(_RNext, static_cast<size_t>(_Digits_written), _First);
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return {_First + _Digits_written, errc{}};
}

inline to_chars_result to_chars(char* const _First, char* const _Last, const char _Value, const int _Base = 10) noexcept
_CONSTEXPR23 to_chars_result to_chars(
char* const _First, char* const _Last, const char _Value, const int _Base = 10) noexcept
/* strengthened */ {
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return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(
_CONSTEXPR23 to_chars_result to_chars(
char* const _First, char* const _Last, const signed char _Value, const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned char _Value,
_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned char _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(
_CONSTEXPR23 to_chars_result to_chars(
char* const _First, char* const _Last, const short _Value, const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned short _Value,
_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned short _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(char* const _First, char* const _Last, const int _Value, const int _Base = 10) noexcept
_CONSTEXPR23 to_chars_result to_chars(
char* const _First, char* const _Last, const int _Value, const int _Base = 10) noexcept
/* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned int _Value,
_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned int _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(char* const _First, char* const _Last, const long _Value, const int _Base = 10) noexcept
_CONSTEXPR23 to_chars_result to_chars(
char* const _First, char* const _Last, const long _Value, const int _Base = 10) noexcept
/* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long _Value,
_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(
_CONSTEXPR23 to_chars_result to_chars(
char* const _First, char* const _Last, const long long _Value, const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
inline to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long long _Value,
_CONSTEXPR23 to_chars_result to_chars(char* const _First, char* const _Last, const unsigned long long _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_to_chars(_First, _Last, _Value, _Base);
}
Expand All @@ -213,27 +216,27 @@ struct from_chars_result {
#endif // _HAS_CXX20
};

_NODISCARD inline unsigned char _Digit_from_char(const char _Ch) noexcept {
// convert ['0', '9'] ['A', 'Z'] ['a', 'z'] to [0, 35], everything else to 255
inline constexpr unsigned char _Digit_from_byte[] = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255,
255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
255, 255, 255, 255, 255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
31, 32, 33, 34, 35, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255};
_STL_INTERNAL_STATIC_ASSERT(_STD size(_Digit_from_byte) == 256);

_NODISCARD _CONSTEXPR23 unsigned char _Digit_from_char(const char _Ch) noexcept {
// convert ['0', '9'] ['A', 'Z'] ['a', 'z'] to [0, 35], everything else to 255
static constexpr unsigned char _Digit_from_byte[] = {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255,
255, 255, 255, 255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 33, 34, 35, 255, 255, 255, 255, 255, 255, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255};
_STL_INTERNAL_STATIC_ASSERT(_STD size(_Digit_from_byte) == 256);

return _Digit_from_byte[static_cast<unsigned char>(_Ch)];
}

template <class _RawTy>
_NODISCARD from_chars_result _Integer_from_chars(
_NODISCARD _CONSTEXPR23 from_chars_result _Integer_from_chars(
const char* const _First, const char* const _Last, _RawTy& _Raw_value, const int _Base) noexcept {
_Adl_verify_range(_First, _Last);
_STL_ASSERT(_Base >= 2 && _Base <= 36, "invalid base in from_chars()");
Expand Down Expand Up @@ -309,47 +312,47 @@ _NODISCARD from_chars_result _Integer_from_chars(
return {_Next, errc{}};
}

inline from_chars_result from_chars(
_CONSTEXPR23 from_chars_result from_chars(
const char* const _First, const char* const _Last, char& _Value, const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, signed char& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, signed char& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned char& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned char& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, short& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, short& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned short& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned short& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(
_CONSTEXPR23 from_chars_result from_chars(
const char* const _First, const char* const _Last, int& _Value, const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned int& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned int& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(
_CONSTEXPR23 from_chars_result from_chars(
const char* const _First, const char* const _Last, long& _Value, const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, long long& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, long long& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
inline from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long long& _Value,
_CONSTEXPR23 from_chars_result from_chars(const char* const _First, const char* const _Last, unsigned long long& _Value,
const int _Base = 10) noexcept /* strengthened */ {
return _Integer_from_chars(_First, _Last, _Value, _Base);
}
Expand Down
2 changes: 2 additions & 0 deletions stl/inc/yvals_core.h
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Expand Up @@ -321,6 +321,7 @@
// P2166R1 Prohibiting basic_string And basic_string_view Construction From nullptr
// P2186R2 Removing Garbage Collection Support
// P2273R3 constexpr unique_ptr
// P2291R3 constexpr Integral <charconv>
// P2302R4 ranges::contains, ranges::contains_subrange
// P2321R2 zip
// (changes to pair, tuple, and vector<bool>::reference only)
Expand Down Expand Up @@ -1496,6 +1497,7 @@ _EMIT_STL_ERROR(STL1004, "C++98 unexpected() is incompatible with C++23 unexpect
#define __cpp_lib_bind_back 202202L
#define __cpp_lib_byteswap 202110L
#define __cpp_lib_constexpr_bitset 202207L
#define __cpp_lib_constexpr_charconv 202207L
#define __cpp_lib_constexpr_typeinfo 202106L

#ifdef __cpp_lib_concepts
Expand Down
84 changes: 57 additions & 27 deletions tests/std/tests/P0067R5_charconv/test.cpp
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Expand Up @@ -197,9 +197,11 @@ void test_common_to_chars(
}

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I guess we can avoid using internal mechanisms in test file by replacing them with the following... (no change requested)

Suggested change
#if _HAS_CXX23 // testing constexpr overloads for integral types in C++23 (P2291R3)
#define CONSTEXPR23 constexpr
constexpr is_runtime_evaluated() noexcept {
return !is_constant_evaluated();
}
#else // ^^^ _HAS_CXX23 / vvv !_HAS_CXX23
#define CONSTEXPR23 inline
constexpr is_runtime_evaluated() noexcept {
return true;
}
#endif // _HAS_CXX23

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Yes, we could do something like that in the future, possibly centralized in a lightweight classic header.

For the time being, tests don't need to strenuously avoid internal machinery and macros as long as there is reasonable justification.

template <typename T>
void test_integer_to_chars(const T value, const optional<int> opt_base, const string_view correct) {

test_common_to_chars(value, opt_base, nullopt, correct);
_CONSTEXPR23 void test_integer_to_chars(const T value, const optional<int> opt_base, const string_view correct) {
// This reaches constexpr step limit to quickly
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if (!_Is_constant_evaluated()) {
test_common_to_chars(value, opt_base, nullopt, correct);
}

{ // Also test successful from_chars() scenarios.
const char* const correct_first = correct.data();
Expand Down Expand Up @@ -387,7 +389,7 @@ constexpr pair<int64_t, array<const char*, 37>> output_negative[] = {
};

template <typename T>
void test_integer_to_chars() {
_CONSTEXPR23 bool test_integer_to_chars() {
for (int base = 2; base <= 36; ++base) {
test_integer_to_chars(static_cast<T>(0), base, "0");
test_integer_to_chars(static_cast<T>(1), base, "1");
Expand All @@ -413,12 +415,14 @@ void test_integer_to_chars() {
}

test_integer_to_chars(static_cast<T>(42), nullopt, "42");

return true;
}

enum class TestFromCharsMode { Normal, SignalingNaN };

template <typename T, typename BaseOrFmt>
void test_from_chars(const string_view input, const BaseOrFmt base_or_fmt, const size_t correct_idx,
_CONSTEXPR23 void test_from_chars(const string_view input, const BaseOrFmt base_or_fmt, const size_t correct_idx,
const errc correct_ec, const optional<T> opt_correct = nullopt,
const TestFromCharsMode mode = TestFromCharsMode::Normal) {

Expand Down Expand Up @@ -460,7 +464,17 @@ constexpr errc inv_arg = errc::invalid_argument;
constexpr errc out_ran = errc::result_out_of_range;

template <typename T>
void test_integer_from_chars() {
_CONSTEXPR23 bool test_integer_from_chars() {
string hundred_zeroes = string(100, '0');
string hundred_zeroes_and_11 = hundred_zeroes + "11"s;
string minus_hundred_zeroes = "-"s + hundred_zeroes;
string minus_hundred_zeroes_and_11 = "-"s + hundred_zeroes_and_11;

string hundred_ones = string(100, '1');
string hundred_ones_and_atatat = hundred_ones + "@@@"s;
string minus_hundred_ones = "-"s + hundred_ones;
string minus_hundred_ones_and_atatat = "-"s + hundred_ones_and_atatat;
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for (int base = 2; base <= 36; ++base) {
test_from_chars<T>("", base, 0, inv_arg); // no characters
test_from_chars<T>("@1", base, 0, inv_arg); // '@' is bogus
Expand Down Expand Up @@ -497,14 +511,14 @@ void test_integer_from_chars() {
}

// Test leading zeroes.
test_from_chars<T>(string(100, '0'), base, 100, errc{}, static_cast<T>(0));
test_from_chars<T>(string(100, '0') + "11"s, base, 102, errc{}, static_cast<T>(base + 1));
test_from_chars<T>(hundred_zeroes, base, 100, errc{}, static_cast<T>(0));
test_from_chars<T>(hundred_zeroes_and_11, base, 102, errc{}, static_cast<T>(base + 1));

// Test negative zero and negative leading zeroes.
if constexpr (is_signed_v<T>) {
test_from_chars<T>("-0", base, 2, errc{}, static_cast<T>(0));
test_from_chars<T>("-"s + string(100, '0'), base, 101, errc{}, static_cast<T>(0));
test_from_chars<T>("-"s + string(100, '0') + "11"s, base, 103, errc{}, static_cast<T>(-base - 1));
test_from_chars<T>(minus_hundred_zeroes, base, 101, errc{}, static_cast<T>(0));
test_from_chars<T>(minus_hundred_zeroes_and_11, base, 103, errc{}, static_cast<T>(-base - 1));
}

// N4713 23.20.3 [charconv.from.chars]/1 "The member ptr of the return value points to the
Expand All @@ -513,12 +527,12 @@ void test_integer_from_chars() {
test_from_chars<T>("11@@@", base, 2, errc{}, static_cast<T>(base + 1));

// When overflowing, we need to keep consuming valid digits, in order to return ptr correctly.
test_from_chars<T>(string(100, '1'), base, 100, out_ran);
test_from_chars<T>(string(100, '1') + "@@@"s, base, 100, out_ran);
test_from_chars<T>(hundred_ones, base, 100, out_ran);
test_from_chars<T>(hundred_ones_and_atatat, base, 100, out_ran);

if constexpr (is_signed_v<T>) {
test_from_chars<T>("-"s + string(100, '1'), base, 101, out_ran);
test_from_chars<T>("-"s + string(100, '1') + "@@@"s, base, 101, out_ran);
test_from_chars<T>(minus_hundred_ones, base, 101, out_ran);
test_from_chars<T>(minus_hundred_ones_and_atatat, base, 101, out_ran);
}
}

Expand All @@ -538,27 +552,22 @@ void test_integer_from_chars() {
test_from_chars<T>("-0x1729", 16, 2, errc{}, static_cast<T>(0)); // reads "-0", stops at 'x'
test_from_chars<T>("-0X1729", 16, 2, errc{}, static_cast<T>(0)); // reads "-0", stops at 'X'
}

return true;
}

template <typename T>
void test_integer() {
test_integer_to_chars<T>();
test_integer_from_chars<T>();
}

void all_integer_tests() {
test_integer<char>();
test_integer<signed char>();
test_integer<unsigned char>();
test_integer<short>();
test_integer<unsigned short>();
test_integer<int>();
test_integer<unsigned int>();
test_integer<long>();
test_integer<unsigned long>();
test_integer<long long>();
test_integer<unsigned long long>();
#if _HAS_CXX23
static_assert(test_integer_to_chars<T>());
static_assert(test_integer_from_chars<T>());
#endif // _HAS_CXX23
}

_CONSTEXPR23 bool test_integer_overflow_scenarios() {
// Test overflow scenarios.
test_from_chars<unsigned int>("4294967289", 10, 10, errc{}, 4294967289U); // not risky
test_from_chars<unsigned int>("4294967294", 10, 10, errc{}, 4294967294U); // risky with good digit
Expand All @@ -577,6 +586,27 @@ void all_integer_tests() {
test_from_chars<int>("-2147483648", 10, 11, errc{}, -2147483647 - 1); // risky with max digit
test_from_chars<int>("-2147483649", 10, 11, out_ran); // risky with bad digit
test_from_chars<int>("-2147483650", 10, 11, out_ran); // beyond risky

return true;
}

void all_integer_tests() {
test_integer<char>();
test_integer<signed char>();
test_integer<unsigned char>();
test_integer<short>();
test_integer<unsigned short>();
test_integer<int>();
test_integer<unsigned int>();
test_integer<long>();
test_integer<unsigned long>();
test_integer<long long>();
test_integer<unsigned long long>();

test_integer_overflow_scenarios();
#if _HAS_CXX23
static_assert(test_integer_overflow_scenarios());
#endif // _HAS_CXX23
}

void assert_message_bits(const bool b, const char* const msg, const uint32_t bits) {
Expand Down
14 changes: 14 additions & 0 deletions tests/std/tests/VSO_0157762_feature_test_macros/test.compile.pass.cpp
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Expand Up @@ -500,6 +500,20 @@ STATIC_ASSERT(__cpp_lib_constexpr_bitset == 202207L);
#endif
#endif

#if _HAS_CXX23
#ifndef __cpp_lib_constexpr_charconv
#error __cpp_lib_constexpr_charconv is not defined
#elif __cpp_lib_constexpr_charconv != 202207L
#error __cpp_lib_constexpr_charconv is not 202207L
#else
STATIC_ASSERT(__cpp_lib_constexpr_charconv == 202207L);
#endif
#else
#ifdef __cpp_lib_constexpr_charconv
#error __cpp_lib_constexpr_charconv is defined
#endif
#endif

#if _HAS_CXX20
#ifndef __cpp_lib_constexpr_complex
#error __cpp_lib_constexpr_complex is not defined
Expand Down