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libstdc++: Use deducing this in std::not_fn when available [PR111327] 

Implement the perfect forwarding required by std::not_fn using deducing
this when available, instead of needing 8 operator() overloads.  This
also fixes Jiang An's test from this PR which would be messy to fix in
the old implementation.

	PR libstdc++/111327

libstdc++-v3/ChangeLog:

	* include/std/functional (_Not_fn::operator())
	[_GLIBCXX_EXPLICIT_THIS_PARAMETER]: Define as a single
	overload using deducing this.
	* testsuite/20_util/function_objects/not_fn/111327.cc: Extend test.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
This commit is contained in:
Patrick Palka 2025-12-05 12:14:23 -05:00
parent 101f968476
commit 756e32a160
2 changed files with 32 additions and 3 deletions
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16
libstdc++-v3/include/std/functional
View File

@ -1056,6 +1056,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_Not_fn(_Not_fn&& __fn) = default;
~_Not_fn() = default;
#if _GLIBCXX_EXPLICIT_THIS_PARAMETER
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wc++23-extensions" // deducing this
template<typename _Self, typename... _Args>
_GLIBCXX20_CONSTEXPR
decltype(_S_not<__inv_res_t<__like_t<_Self, _Fn>, _Args...>>())
operator()(this _Self&& __self, _Args&&... __args)
noexcept(__is_nothrow_invocable<__like_t<_Self, _Fn>, _Args...>::value
&& noexcept(_S_not<__inv_res_t<__like_t<_Self, _Fn>, _Args...>>()))
{
return !std::__invoke(__like_t<_Self, _Not_fn>(__self)._M_fn,
std::forward<_Args>(__args)...);
}
# pragma GCC diagnostic pop
#else
// Macro to define operator() with given cv-qualifiers ref-qualifiers,
// forwarding _M_fn and the function arguments with the same qualifiers,
// and deducing the return type and exception-specification.
@ -1081,6 +1096,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_NOT_FN_CALL_OP( && )
_GLIBCXX_NOT_FN_CALL_OP( const && )
#undef _GLIBCXX_NOT_FN_CALL_OP
#endif
private:
_Fn _M_fn;

19
libstdc++-v3/testsuite/20_util/function_objects/not_fn/111327.cc
View File

@ -15,15 +15,28 @@ struct G {
bool operator()(...) const &&;
};
struct Weird {
void operator()();
bool operator()() const { return true; }
};
int main() {
auto f = std::not_fn(F{});
f(); // { dg-error "deleted" }
f(); // { dg-error "no match" }
std::move(f)();
std::as_const(f)();
std::move(std::as_const(f))();
auto g = std::not_fn(G{});
g(); // { dg-error "deleted" }
std::move(g)(); // { dg-error "deleted" }
g(); // { dg-error "no match" }
std::move(g)(); // { dg-error "no match" }
std::move(std::as_const(g))();
auto h = std::not_fn(Weird{});
h(); // { dg-error "no match" }
}
// { dg-error "no type named 'type' in 'struct std::__invoke_result<" "" { target *-*-* } 0 }
// { dg-error "no matching function for call to 'std::_Not_fn<Weird>" "" { target *-*-* } 0 }
// { dg-error "could not convert 'std::declval<void>\\(\\)' from 'void' to 'bool'" "" { target *-*-* } 0 }
// { dg-error "in argument to unary !" "" { target *-*-* } 0 }