On Tue, 12 Sept 2023 at 02:11, Patrick Palka via Libstdc++
<libstd...@gcc.gnu.org> wrote:
>
> The previous patch fixed perfect forwarding for std::bind_front.
> This patch fixes the same issue for std::not_fn.
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk and
> perhaps 13?
Yes for both, thanks.
>
> PR libstdc++/111327
>
> libstdc++-v3/ChangeLog:
>
> * include/std/functional (_GLIBCXX_NOT_FN_CALL_OP): Also define
> a deleted fallback operator() overload. Constrain both the
> main and deleted overloads accordingly.
> * testsuite/20_util/function_objects/not_fn/111327.cc: New test.
> ---
> libstdc++-v3/include/std/functional | 10 +++++--
> .../20_util/function_objects/not_fn/111327.cc | 29 +++++++++++++++++++
> 2 files changed, 37 insertions(+), 2 deletions(-)
> create mode 100644
> libstdc++-v3/testsuite/20_util/function_objects/not_fn/111327.cc
>
> diff --git a/libstdc++-v3/include/std/functional
> b/libstdc++-v3/include/std/functional
> index c50b9e4d365..9551e38dfdb 100644
> --- a/libstdc++-v3/include/std/functional
> +++ b/libstdc++-v3/include/std/functional
> @@ -1061,7 +1061,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> // forwarding _M_fn and the function arguments with the same
> qualifiers,
> // and deducing the return type and exception-specification.
> #define _GLIBCXX_NOT_FN_CALL_OP( _QUALS ) \
> - template<typename... _Args> \
> + template<typename... _Args, \
> + typename = enable_if_t<__is_invocable<_Fn _QUALS,
> _Args...>::value>> \
> _GLIBCXX20_CONSTEXPR \
> decltype(_S_not<__inv_res_t<_Fn _QUALS, _Args...>>()) \
> operator()(_Args&&... __args) _QUALS \
> @@ -1070,7 +1071,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> { \
> return !std::__invoke(std::forward< _Fn _QUALS >(_M_fn), \
> std::forward<_Args>(__args)...); \
> - }
> + } \
> + \
> + template<typename... _Args, \
> + typename = enable_if_t<!__is_invocable<_Fn _QUALS,
> _Args...>::value>> \
> + void operator()(_Args&&... __args) _QUALS = delete;
> +
> _GLIBCXX_NOT_FN_CALL_OP( & )
> _GLIBCXX_NOT_FN_CALL_OP( const & )
> _GLIBCXX_NOT_FN_CALL_OP( && )
> diff --git a/libstdc++-v3/testsuite/20_util/function_objects/not_fn/111327.cc
> b/libstdc++-v3/testsuite/20_util/function_objects/not_fn/111327.cc
> new file mode 100644
> index 00000000000..93e00ee8057
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/20_util/function_objects/not_fn/111327.cc
> @@ -0,0 +1,29 @@
> +// PR libstdc++/111327 - std::bind_front (and std::not_fn) doesn't perfectly
> +// forward according to value category of the call wrapper object
> +// { dg-do compile { target c++17 } }
> +
> +#include <functional>
> +#include <utility>
> +
> +struct F {
> + void operator()(...) & = delete;
> + bool operator()(...) const &;
> +};
> +
> +struct G {
> + void operator()(...) && = delete;
> + bool operator()(...) const &&;
> +};
> +
> +int main() {
> + auto f = std::not_fn(F{});
> + f(); // { dg-error "deleted" }
> + 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" }
> + std::move(std::as_const(g))();
> +}
> --
> 2.42.0.158.g94e83dcf5b
>
