procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

libstdc++: Implement spaceship for std::array (P1614R2)

Browse source 
As done for std::pair, this defines operator<=> as a non-member function
template and does not alter operator==, as expected to be proposed as
the resolution to an unpublished LWG issue.

Instead of calling std::lexicographical_compare_three_way the <=>
overload is implemented by hand to take advantage of the fact the
element types and array sizes are known to be the same.

	* include/bits/cpp_type_traits.h (__is_byte<char8_t>): Add
	specialization.
	* include/std/array (operator<=>): Likewise.
	* testsuite/23_containers/array/comparison_operators/constexpr.cc:
	Test three-way comparisons and arrays of unsigned char.
	* testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
	dg-error line numbers.

From-SVN: r278981
This commit is contained in:
Jonathan Wakely 2019-12-05 00:42:06 +00:00 • committed by Jonathan Wakely
parent 880c7b8c25
commit 3a4cc6281b
5 changed files with 62 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

10
libstdc++-v3/ChangeLog
View file

@ -1,3 +1,13 @@
2019-12-05 Jonathan Wakely <jwakely@redhat.com>
* include/bits/cpp_type_traits.h (__is_byte<char8_t>): Add
specialization.
* include/std/array (operator<=>): Likewise.
* testsuite/23_containers/array/comparison_operators/constexpr.cc:
Test three-way comparisons and arrays of unsigned char.
* testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust
dg-error line numbers.
2019-12-03 Jonathan Wakely <jwakely@redhat.com>
* include/bits/stl_pair.h [__cpp_lib_three_way_comparison]

9
libstdc++-v3/include/bits/cpp_type_traits.h
View file

@ -411,6 +411,15 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
};
#endif // C++17
#ifdef _GLIBCXX_USE_CHAR8_T
template<>
struct __is_byte<char8_t>
{
enum { __value = 1 };
typedef __true_type __type;
};
#endif
//
// Move iterator type
//

20
libstdc++-v3/include/std/array
View file

@ -253,6 +253,25 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
{ return std::equal(__one.begin(), __one.end(), __two.begin()); }
#if __cpp_lib_three_way_comparison && __cpp_lib_concepts
template<typename _Tp, size_t _Nm>
constexpr __detail::__synth3way_t<_Tp>
operator<=>(const array<_Tp, _Nm>& __a, const array<_Tp, _Nm>& __b)
{
if constexpr (_Nm && __is_byte<_Tp>::__value)
return __builtin_memcmp(__a.data(), __b.data(), _Nm) <=> 0;
else
{
for (size_t __i = 0; __i < _Nm; ++__i)
{
auto __c = __detail::__synth3way(__a[__i], __b[__i]);
if (__c != 0)
return __c;
}
}
return strong_ordering::equal;
}
#else
template<typename _Tp, std::size_t _Nm>
_GLIBCXX20_CONSTEXPR
inline bool
@ -285,6 +304,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
inline bool
operator>=(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
{ return !(__one < __two); }
#endif // three_way_comparison && concepts
// Specialized algorithms.
template<typename _Tp, std::size_t _Nm>

20
libstdc++-v3/testsuite/23_containers/array/comparison_operators/constexpr.cc
View file

@ -31,3 +31,23 @@ static_assert(a1 < a3);
static_assert(a4 > a1);
static_assert(a1 <= a3);
static_assert(a4 >= a1);
static_assert(std::is_eq(a1 <=> a1));
static_assert(std::is_neq(a1 <=> a2));
static_assert(std::is_lt(a1 <=> a3));
static_assert(std::is_gt(a4 <=> a1));
constexpr std::array<unsigned char, 3> a5{{1, 2, 3}};
constexpr std::array<unsigned char, 3> a6{{4, 5, 6}};
constexpr std::array<unsigned char, 3> a7{{1, 2, 4}};
constexpr std::array<unsigned char, 3> a8{{1, 3, 3}};
static_assert(a5 == a5);
static_assert(a5 != a6);
static_assert(a5 < a7);
static_assert(a8 > a5);
static_assert(a5 <= a7);
static_assert(a8 >= a5);
static_assert(std::is_eq(a5 <=> a5));
static_assert(std::is_neq(a5 <=> a6));
static_assert(std::is_lt(a5 <=> a7));
static_assert(std::is_gt(a8 <=> a5));

6
libstdc++-v3/testsuite/23_containers/array/tuple_interface/get_neg.cc
View file

@ -27,6 +27,6 @@ int n1 = std::get<1>(a);
int n2 = std::get<1>(std::move(a));
int n3 = std::get<1>(ca);
// { dg-error "static assertion failed" "" { target *-*-* } 316 }
// { dg-error "static assertion failed" "" { target *-*-* } 325 }
// { dg-error "static assertion failed" "" { target *-*-* } 333 }
// { dg-error "static assertion failed" "" { target *-*-* } 336 }
// { dg-error "static assertion failed" "" { target *-*-* } 345 }
// { dg-error "static assertion failed" "" { target *-*-* } 353 }