On Thu, 25 Jul 2024 at 01:04, Patrick Palka <ppa...@redhat.com> wrote: > > Tested on x86_64-pc-linux-gnu, does this look OK for trunk/14 (after > 14.2 is released)?
Yes to both, thanks. > > -- >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 >
