On Tue, Apr 29, 2025 at 11:01 AM Jonathan Wakely <jwak...@redhat.com> wrote:
> This allows removing the _Target_handler class template, because it's no
> longer needed to prevent instantiating invalid specializations of
> _Function_handler.
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/std_function.h (_Target_handler): Remove.
> (function::target): Use constexpr-if for C++11 and
> C++14, with diagnostic pragmas to suppress warnings.
> ---
>
> Tested x86_64-linux.
>
LGTM.
>
> libstdc++-v3/include/bits/std_function.h | 31 +++++++-----------------
> 1 file changed, 9 insertions(+), 22 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/std_function.h
> b/libstdc++-v3/include/bits/std_function.h
> index 1bf8b9ad6e8..3bfbe824026 100644
> --- a/libstdc++-v3/include/bits/std_function.h
> +++ b/libstdc++-v3/include/bits/std_function.h
> @@ -135,13 +135,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> static _Functor*
> _M_get_pointer(const _Any_data& __source) noexcept
> {
> - if _GLIBCXX17_CONSTEXPR (__stored_locally)
> +#pragma GCC diagnostic push
> +#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
> + if constexpr (__stored_locally)
> {
> const _Functor& __f = __source._M_access<_Functor>();
> return const_cast<_Functor*>(std::__addressof(__f));
> }
> else // have stored a pointer
> return __source._M_access<_Functor*>();
> +#pragma GCC diagnostic pop
> }
>
> private:
> @@ -312,21 +315,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> { return false; }
> };
>
> - // Avoids instantiating ill-formed specializations of _Function_handler
> - // in std::function<_Signature>::target<_Functor>().
> - // e.g. _Function_handler<Sig, void()> and _Function_handler<Sig, void>
> - // would be ill-formed.
> - template<typename _Signature, typename _Functor,
> - bool __valid = is_object<_Functor>::value>
> - struct _Target_handler
> - : _Function_handler<_Signature, typename remove_cv<_Functor>::type>
> - { };
> -
> - template<typename _Signature, typename _Functor>
> - struct _Target_handler<_Signature, _Functor, false>
> - : _Function_handler<void, void>
> - { };
> -
> /**
> * @brief Polymorphic function wrapper.
> * @ingroup functors
> @@ -644,13 +632,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> const _Functor*
> target() const noexcept
> {
> - if _GLIBCXX17_CONSTEXPR (is_object<_Functor>::value)
> +#pragma GCC diagnostic push
> +#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
> + if constexpr (is_object<_Functor>::value)
> {
> - // For C++11 and C++14 if-constexpr is not used above, so
> - // _Target_handler avoids ill-formed _Function_handler types.
> - using _Handler = _Target_handler<_Res(_ArgTypes...),
> _Functor>;
> -
> - if (_M_manager == &_Handler::_M_manager
> + if (_M_manager == &_Handler<_Functor>::_M_manager
> #if __cpp_rtti
> || (_M_manager && typeid(_Functor) == target_type())
> #endif
> @@ -661,6 +647,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> return __ptr._M_access<const _Functor*>();
> }
> }
> +#pragma GCC diagnostic pop
> return nullptr;
> }
> /// @}
> --
> 2.49.0
>
>
