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Workaround libcxx issue

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This commit is contained in:
Simon Brand
2018-09-03 12:10:22 +01:00
parent fd6c65e7f9
commit 068d3db664
1 changed files with 26 additions and 0 deletions
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26
tl/optional.hpp
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@ -139,9 +139,35 @@ template <class B, class... Bs>
struct conjunction<B, Bs...>
: std::conditional<bool(B::value), conjunction<Bs...>, B>::type {};
// In C++11 mode, there's an issue in libc++'s std::mem_fn
// which results in a hard-error when using it in a noexcept expression
// in some cases. This is a check to workaround the common failing case.
#ifdef TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND
template <class T> struct is_pointer_to_non_const_member_func : std::false_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...)> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...)&> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...)&&> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...) volatile> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...) volatile&> : std::true_type{};
template <class T, class Ret, class... Args>
struct is_pointer_to_non_const_member_func<Ret (T::*) (Args...) volatile&&> : std::true_type{};
template <class T> struct is_ref_to_const : std::false_type{};
template <class T> struct is_ref_to_const<T const&> : std::true_type{};
#endif
// std::invoke from C++17
// https://stackoverflow.com/questions/38288042/c11-14-invoke-workaround
template <typename Fn, typename... Args,
#ifdef TL_OPTIONAL_LIBCXX_MEM_FN_WORKAROUND
typename = enable_if_t<!(is_pointer_to_non_const_member_func<Fn>::value
&& is_ref_to_const<Args...>::value)>,
#endif
typename = enable_if_t<std::is_member_pointer<decay_t<Fn>>{}>,
int = 0>
constexpr auto invoke(Fn &&f, Args &&... args) noexcept(