On Fri, 12 Jan 2024 at 20:09, Patrick Palka <ppa...@redhat.com> wrote:
>
> This simplifies the operator() of _Bind_front using C++23 deducing
> this, allowing us to condense multiple nearly identical operator()
> overloads into one.
>
> In passing I think we can remove _Bind_front's defaulted special member
> declarations and just let the compiler implicitly generate them for us.
OK
>
> libstdc++-v3/ChangeLog:
>
> * include/std/functional (_Bind_front): Remove =default special
> member function declarations.
> (_Bind_front::operator()): Implement using C++23 deducing this
> when available.
> * testsuite/20_util/function_objects/bind_front/111327.cc:
> Adjust testcase to expect better errors in C++23 mode.
> ---
> libstdc++-v3/include/std/functional | 20 +++++++++++++------
> .../function_objects/bind_front/111327.cc | 14 +++++++------
> 2 files changed, 22 insertions(+), 12 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/functional
> b/libstdc++-v3/include/std/functional
> index 8d50a730889..190cea612bb 100644
> --- a/libstdc++-v3/include/std/functional
> +++ b/libstdc++-v3/include/std/functional
> @@ -934,12 +934,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> _M_bound_args(std::forward<_Args>(__args)...)
> { static_assert(sizeof...(_Args) == sizeof...(_BoundArgs)); }
>
> - _Bind_front(const _Bind_front&) = default;
> - _Bind_front(_Bind_front&&) = default;
> - _Bind_front& operator=(const _Bind_front&) = default;
> - _Bind_front& operator=(_Bind_front&&) = default;
> - ~_Bind_front() = default;
> -
> +#if __cpp_explicit_this_parameter
> + template<typename _Self, typename... _CallArgs>
> + constexpr
> + invoke_result_t<__like_t<_Self, _Fd>, __like_t<_Self, _BoundArgs>...,
> _CallArgs...>
> + operator()(this _Self&& __self, _CallArgs&&... __call_args)
> + noexcept(is_nothrow_invocable_v<__like_t<_Self, _Fd>,
> + __like_t<_Self, _BoundArgs>...,
> + _CallArgs...>)
> + {
> + return _S_call(std::forward<_Self>(__self), _BoundIndices(),
> + std::forward<_CallArgs>(__call_args)...);
> + }
> +#else
> template<typename... _CallArgs>
> requires true
> constexpr
> @@ -997,6 +1004,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
> template<typename... _CallArgs>
> void operator()(_CallArgs&&...) const && = delete;
> +#endif
>
> private:
> using _BoundIndices = index_sequence_for<_BoundArgs...>;
> diff --git
> a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
> b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
> index 43b56ca4378..5fe0a83baec 100644
> --- a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
> +++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
> @@ -17,24 +17,26 @@ struct G {
>
> int main() {
> auto f0 = std::bind_front(F{});
> - f0(); // { dg-error "deleted" }
> + f0(); // { dg-error "deleted|no match" }
> std::move(f0)();
> std::as_const(f0)();
> std::move(std::as_const(f0))();
>
> auto g0 = std::bind_front(G{});
> - g0(); // { dg-error "deleted" }
> - std::move(g0)(); // { dg-error "deleted" }
> + g0(); // { dg-error "deleted|no match" }
> + std::move(g0)(); // { dg-error "deleted|no match" }
> std::move(std::as_const(g0))();
>
> auto f1 = std::bind_front(F{}, 42);
> - f1(); // { dg-error "deleted" }
> + f1(); // { dg-error "deleted|no match" }
> std::move(f1)();
> std::as_const(f1)();
> std::move(std::as_const(f1))();
>
> auto g1 = std::bind_front(G{}, 42);
> - g1(); // { dg-error "deleted" }
> - std::move(g1)(); // { dg-error "deleted" }
> + g1(); // { dg-error "deleted|no match" }
> + std::move(g1)(); // { dg-error "deleted|no match" }
> std::move(std::as_const(g1))();
> }
> +
> +// { dg-error "no type named 'type' in 'struct std::invoke_result" "" {
> target c++23 } 0 }
> --
> 2.43.0.283.ga54a84b333
>
