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Make pointer_to SFINAE friendlier

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This commit is contained in:
Glen Fernandes
2021-12-15 09:31:34 -05:00
parent a121ab0278
commit 78dd0cce2f
2 changed files with 70 additions and 42 deletions
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include/boost/core/pointer_traits.hpp
+50 -19
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@@ -106,43 +106,74 @@ struct ptr_rebind<T, U,
typedef typename T::template rebind<U> type;
};
template<class>
struct ptr_void {
#if !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
template<class T, class E>
class ptr_to_expr {
template<class>
struct result {
char x, y;
};
static E& source();
template<class O>
static auto check(int) -> result<decltype(O::pointer_to(source()))>;
template<class>
static char check(long);
public:
BOOST_STATIC_CONSTEXPR bool value = sizeof(check<T>(0)) != 1;
};
template<class T, class E>
struct ptr_to_expr<T*, E> {
BOOST_STATIC_CONSTEXPR bool value = true;
};
template<class T, class E>
struct ptr_has_to {
BOOST_STATIC_CONSTEXPR bool value = ptr_to_expr<T, E>::value;
};
#else
template<class, class>
struct ptr_has_to {
BOOST_STATIC_CONSTEXPR bool value = true;
};
#endif
template<class T>
struct ptr_has_to<T, void> {
BOOST_STATIC_CONSTEXPR bool value = false;
};
template<>
struct ptr_void<void> {
BOOST_STATIC_CONSTEXPR bool value = true;
template<class T>
struct ptr_has_to<T, const void> {
BOOST_STATIC_CONSTEXPR bool value = false;
};
template<>
struct ptr_void<const void> {
BOOST_STATIC_CONSTEXPR bool value = true;
template<class T>
struct ptr_has_to<T, volatile void> {
BOOST_STATIC_CONSTEXPR bool value = false;
};
template<>
struct ptr_void<volatile void> {
BOOST_STATIC_CONSTEXPR bool value = true;
template<class T>
struct ptr_has_to<T, const volatile void> {
BOOST_STATIC_CONSTEXPR bool value = false;
};
template<>
struct ptr_void<const volatile void> {
BOOST_STATIC_CONSTEXPR bool value = true;
};
template<class, class E, bool = ptr_void<E>::value>
template<class T, class E, bool = ptr_has_to<T, E>::value>
struct ptr_to { };
template<class T, class E>
struct ptr_to<T, E, false> {
struct ptr_to<T, E, true> {
static T pointer_to(E& v) {
return T::pointer_to(v);
}
};
template<class T>
struct ptr_to<T*, T, false> {
struct ptr_to<T*, T, true> {
static T* pointer_to(T& v) BOOST_NOEXCEPT {
return boost::addressof(v);
}