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PR libstdc++/82262 fix std::hash<std::optional<const T>>

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PR libstdc++/82262
	* include/std/optional (__optional_hash_call_base): Add template
	parameter for remove_const_t<_Tp> and use it consistently.
	* testsuite/20_util/optional/hash.cc: Test optional<const T>.

From-SVN: r253010
This commit is contained in:
Jonathan Wakely 2017-09-20 14:24:45 +01:00 committed by Jonathan Wakely
parent 3c16e99cf7
commit f6b05c44aa
3 changed files with 26 additions and 10 deletions
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7
libstdc++-v3/ChangeLog
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@ -1,3 +1,10 @@
2017-09-20 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/82262
* include/std/optional (__optional_hash_call_base): Add template
parameter for remove_const_t<_Tp> and use it consistently.
* testsuite/20_util/optional/hash.cc: Test optional<const T>.
2017-09-19 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/71500

12
libstdc++-v3/include/std/optional
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@ -1005,23 +1005,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Hash.
template<typename _Tp, bool
= __poison_hash<remove_const_t<_Tp>>::__enable_hash_call>
template<typename _Tp, typename _Up = remove_const_t<_Tp>,
bool = __poison_hash<_Up>::__enable_hash_call>
struct __optional_hash_call_base
{
size_t
operator()(const optional<_Tp>& __t) const
noexcept(noexcept(hash<_Tp> {}(*__t)))
noexcept(noexcept(hash<_Up>{}(*__t)))
{
// We pick an arbitrary hash for disengaged optionals which hopefully
// usual values of _Tp won't typically hash to.
constexpr size_t __magic_disengaged_hash = static_cast<size_t>(-3333);
return __t ? hash<_Tp> {}(*__t) : __magic_disengaged_hash;
return __t ? hash<_Up>{}(*__t) : __magic_disengaged_hash;
}
};
template<typename _Tp>
struct __optional_hash_call_base<_Tp, false> {};
template<typename _Tp, typename _Up>
struct __optional_hash_call_base<_Tp, _Up, false> {};
template<typename _Tp>
struct hash<optional<_Tp>>

17
libstdc++-v3/testsuite/20_util/optional/hash.cc
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@ -29,14 +29,23 @@ template<class T>
auto f(...) -> decltype(std::false_type());
static_assert(!decltype(f<S>(0))::value, "");
static_assert(!std::is_invocable_v<
std::hash<std::optional<S>>&, std::optional<S> const&> );
static_assert(std::is_invocable_v<
std::hash<std::optional<int>>&, std::optional<int> const&> );
template<typename T>
constexpr bool hashable()
{ return std::is_invocable_v<std::hash<T>&, const T&>; }
static_assert(!hashable<std::optional<S>>());
static_assert(!hashable<std::optional<const S>>());
static_assert(hashable<std::optional<int>>());
static_assert(hashable<std::optional<const int>>());
int main()
{
int x = 42;
std::optional<int> x2 = 42;
VERIFY(std::hash<int>()(x) == std::hash<std::optional<int>>()(x2));
// PR libstdc++/82262
std::optional<const int> x3 = x2;
VERIFY(std::hash<int>()(x) == std::hash<std::optional<const int>>()(x3));
}