On Mon, 20 Oct 2025 at 14:30, Tomasz Kamiński <[email protected]> wrote:
>
> Implement resolution of LWG4425.
OK thanks
> libstdc++-v3/ChangeLog:
>
> * include/bits/funcwrap.h (__polyfunc::__deduce_funcref):
> Adjust signature produced for member object pointers.
> * testsuite/20_util/function_ref/deduction.cc: Update tests.
> ---
> Tested on x86_64-linux locally.
>
> libstdc++-v3/include/bits/funcwrap.h | 6 ++++--
> libstdc++-v3/testsuite/20_util/function_ref/deduction.cc | 8 ++++----
> 2 files changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/funcwrap.h
> b/libstdc++-v3/include/bits/funcwrap.h
> index 1a81c9a9b46..67fd591e963 100644
> --- a/libstdc++-v3/include/bits/funcwrap.h
> +++ b/libstdc++-v3/include/bits/funcwrap.h
> @@ -546,8 +546,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> if constexpr (is_member_object_pointer_v<_Fn>)
> {
> if constexpr (is_invocable_v<_Fn, _Tr>)
> - // TODO Consider reporting issue to make this noexcept
> - return static_cast<invoke_result_t<_Fn, _Tr>(*)()>(nullptr);
> + // _GLIBCXX_RESOLVE_LIB_DEFECTS
> + // 4425. CTAD function_ref from data member pointer should
> produce
> + // noexcept signature
> + return static_cast<invoke_result_t<_Fn, _Tr>(*)()
> noexcept>(nullptr);
> }
> else if constexpr (requires { typename __skip_first_arg<_Fn>::type; })
> return static_cast<__skip_first_arg<_Fn>::type*>(nullptr);
> diff --git a/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
> b/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
> index 6ed2b4e5712..b034c7af072 100644
> --- a/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
> +++ b/libstdc++-v3/testsuite/20_util/function_ref/deduction.cc
> @@ -89,13 +89,13 @@ S s{};
> const S cs{};
>
> static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, s)),
> - function_ref<int&()>> );
> + function_ref<int&() noexcept>> );
> static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, cs)),
> - function_ref<const int&()>> );
> + function_ref<const int&() noexcept>> );
> static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, &s)),
> - function_ref<int&()>> );
> + function_ref<int&() noexcept>> );
> static_assert( is_same_v<decltype(function_ref(nontype<&S::mem>, &cs)),
> - function_ref<const int&()>> );
> + function_ref<const int&() noexcept>> );
> static_assert( !deductible<&S::mem, int> );
>
> static_assert( is_same_v<decltype(function_ref(nontype<&S::f>, s)),
> --
> 2.51.0
>
