Tested on x86_64-pc-linux-gnu, does this look OK for trunk/14 (after 14.2 is released)?
-- >8 -- The type of an implicit object parameter is always the current class. For an explicit object parameter however, its deduced type can be a class derived from the current class. So when combining multiple implicit-object overloads into a single explicit-object overload we need to account for this possibility. For example, when accessing a member from the current class through an explicit object parameter, it may be a derived class from which the member is not accessible, as in the below testcases. This pitfall is discussed[1] in the deducing this paper. The general solution is to cast the explicit object parameter to (a reference to) the current class, appropriately qualified, rather than e.g. using std::forward which preserves the deduced type. This patch corrects the existing problematic uses of explicit object parameters in the library, all of which forward the parameter via std::forward, to instead cast the parameter to the current class via our __like_t alias template. Note that unlike the paper's like_t, ours always returns a reference so when can just write __like_t<Self, B>(self) instead of (_like_t<Self, B>&&)self as the paper does. [1]: https://wg21.link/P0847#name-lookup-within-member-functions and the section after that PR libstdc++/116038 libstdc++-v3/ChangeLog: * include/std/functional (_Bind_front::operator()): Use __like_t instead of std::forward when forwarding __self. (_Bind_back::operator()): Likewise. * include/std/ranges (_Partial::operator()): Likewise. (_Pipe::operator()): Likewise. * testsuite/20_util/function_objects/bind_back/116038.cc: New test. * testsuite/20_util/function_objects/bind_front/116038.cc: New test. * testsuite/std/ranges/adaptors/116038.cc: New test. --- libstdc++-v3/include/std/functional | 4 +-- libstdc++-v3/include/std/ranges | 11 ++++--- .../function_objects/bind_back/116038.cc | 27 +++++++++++++++++ .../function_objects/bind_front/116038.cc | 27 +++++++++++++++++ .../testsuite/std/ranges/adaptors/116038.cc | 29 +++++++++++++++++++ 5 files changed, 92 insertions(+), 6 deletions(-) create mode 100644 libstdc++-v3/testsuite/20_util/function_objects/bind_back/116038.cc create mode 100644 libstdc++-v3/testsuite/20_util/function_objects/bind_front/116038.cc create mode 100644 libstdc++-v3/testsuite/std/ranges/adaptors/116038.cc diff --git a/libstdc++-v3/include/std/functional b/libstdc++-v3/include/std/functional index 99364286a72..7788a963757 100644 --- a/libstdc++-v3/include/std/functional +++ b/libstdc++-v3/include/std/functional @@ -944,7 +944,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION noexcept(is_nothrow_invocable_v<__like_t<_Self, _Fd>, __like_t<_Self, _BoundArgs>..., _CallArgs...>) { - return _S_call(std::forward<_Self>(__self), _BoundIndices(), + return _S_call(__like_t<_Self, _Bind_front>(__self), _BoundIndices(), std::forward<_CallArgs>(__call_args)...); } #else @@ -1072,7 +1072,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION noexcept(is_nothrow_invocable_v<__like_t<_Self, _Fd>, _CallArgs..., __like_t<_Self, _BoundArgs>...>) { - return _S_call(std::forward<_Self>(__self), _BoundIndices(), + return _S_call(__like_t<_Self, _Bind_back>(__self), _BoundIndices(), std::forward<_CallArgs>(__call_args)...); } diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index 3f335b95a08..b7c7aa36ddc 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -1033,7 +1033,7 @@ namespace views::__adaptor return _Adaptor{}(std::forward<_Range>(__r), std::forward<decltype(__args)>(__args)...); }; - return std::apply(__forwarder, std::forward<_Self>(__self)._M_args); + return std::apply(__forwarder, __like_t<_Self, _Partial>(__self)._M_args); } #else template<typename _Range> @@ -1082,7 +1082,10 @@ namespace views::__adaptor requires __adaptor_invocable<_Adaptor, _Range, __like_t<_Self, _Arg>> constexpr auto operator()(this _Self&& __self, _Range&& __r) - { return _Adaptor{}(std::forward<_Range>(__r), std::forward<_Self>(__self)._M_arg); } + { + return _Adaptor{}(std::forward<_Range>(__r), + __like_t<_Self, _Partial>(__self)._M_arg); + } #else template<typename _Range> requires __adaptor_invocable<_Adaptor, _Range, const _Arg&> @@ -1185,8 +1188,8 @@ namespace views::__adaptor constexpr auto operator()(this _Self&& __self, _Range&& __r) { - return (std::forward<_Self>(__self)._M_rhs - (std::forward<_Self>(__self)._M_lhs + return (__like_t<_Self, _Pipe>(__self)._M_rhs + (__like_t<_Self, _Pipe>(__self)._M_lhs (std::forward<_Range>(__r)))); } #else diff --git a/libstdc++-v3/testsuite/20_util/function_objects/bind_back/116038.cc b/libstdc++-v3/testsuite/20_util/function_objects/bind_back/116038.cc new file mode 100644 index 00000000000..ed392b1434e --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_back/116038.cc @@ -0,0 +1,27 @@ +// PR libstdc++/116038 +// { dg-do compile { target c++23 } } + +#include <functional> +#include <utility> + +struct A { }; +struct B { }; + +template<class... Ts> +struct overloaded : private Ts... { + overloaded(Ts...); + using Ts::operator()...; +}; + +int apply_a(A, int); +int apply_b(B, int); + +int main() { + overloaded o = { std::bind_back(apply_a, 1), + std::bind_back(apply_b, 2) }; + A a; + o(a); + std::as_const(o)(a); + std::move(o)(a); + std::move(std::as_const(o))(a); +} diff --git a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/116038.cc b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/116038.cc new file mode 100644 index 00000000000..3bf1226375b --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/116038.cc @@ -0,0 +1,27 @@ +// PR libstdc++/116038 +// { dg-do compile { target c++20 } } + +#include <functional> +#include <utility> + +struct A { }; +struct B { }; + +template<class... Ts> +struct overloaded : private Ts... { + overloaded(Ts...); + using Ts::operator()...; +}; + +int apply_a(int, A); +int apply_b(int, B); + +int main() { + overloaded o = { std::bind_front(apply_a, 1), + std::bind_front(apply_b, 2) }; + A a; + o(a); + std::as_const(o)(a); + std::move(o)(a); + std::move(std::as_const(o))(a); +} diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/116038.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/116038.cc new file mode 100644 index 00000000000..1afdf3d06d1 --- /dev/null +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/116038.cc @@ -0,0 +1,29 @@ +// PR libstdc++/116038 +// { dg-do compile { target c++20 } } + +#include <ranges> +#include <utility> + +struct A { }; +struct B { }; + +template<class... Ts> +struct overloaded : private Ts... { + overloaded(Ts...); + using Ts::operator()...; +}; + +int x[5]; +struct integralish { operator int() const; } i; + +int main() { + overloaded o1 = { std::views::drop(i) }; + o1(x); + std::move(o1)(x); + std::as_const(o1)(x); + + overloaded o2 = { std::views::drop(i) | std::views::take(i) }; + o2(x); + std::move(o2)(x); + std::as_const(o1)(x); +} -- 2.46.0.rc2
