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* [gcc r14-3901] libstdc++: Remove std::bind_front specialization for no bound args
@ 2023-09-12 15:27 Patrick Palka
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From: Patrick Palka @ 2023-09-12 15:27 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:f1e87aee5b7023fb4f5791c6869db705e18c2705
commit r14-3901-gf1e87aee5b7023fb4f5791c6869db705e18c2705
Author: Patrick Palka <ppalka@redhat.com>
Date: Tue Sep 12 11:23:08 2023 -0400
libstdc++: Remove std::bind_front specialization for no bound args
The specialization used by std::bind_front when there are no bound args
(added by r13-4214-gcbd05ca5ab1231) seems to be mostly obsoleted by
r13-5033-ge2eab3c4edb6aa which added [[no_unique_address]] to the main
template's data members. What's left to consider is the compile time
advantage of the specialization, which doesn't seem huge since it just
avoids using tuple<> (which is an explicit specialization anyway) and
expanding some pack expansions with an empty argument pack. So this
patch removes this specialization; this means we have one less spot to
fix the PR libstdc++/111327 perfect forwarding bug.
libstdc++-v3/ChangeLog:
* include/std/functional (_Bind_front0): Remove.
(_Bind_front_t): Adjust.
Diff:
---
libstdc++-v3/include/std/functional | 63 +------------------------------------
1 file changed, 1 insertion(+), 62 deletions(-)
diff --git a/libstdc++-v3/include/std/functional b/libstdc++-v3/include/std/functional
index 60d4d1f3dd22..7d1b890bb4e9 100644
--- a/libstdc++-v3/include/std/functional
+++ b/libstdc++-v3/include/std/functional
@@ -996,69 +996,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
[[no_unique_address]] std::tuple<_BoundArgs...> _M_bound_args;
};
- // Avoid the overhead of an empty tuple<> if there are no bound args.
- template<typename _Fd>
- struct _Bind_front0
- {
- static_assert(is_move_constructible_v<_Fd>);
-
- // First parameter is to ensure this constructor is never used
- // instead of the copy/move constructor.
- template<typename _Fn>
- explicit constexpr
- _Bind_front0(int, _Fn&& __fn)
- noexcept(is_nothrow_constructible_v<_Fd, _Fn>)
- : _M_fd(std::forward<_Fn>(__fn))
- { }
-
- _Bind_front0(const _Bind_front0&) = default;
- _Bind_front0(_Bind_front0&&) = default;
- _Bind_front0& operator=(const _Bind_front0&) = default;
- _Bind_front0& operator=(_Bind_front0&&) = default;
- ~_Bind_front0() = default;
-
- template<typename... _CallArgs>
- constexpr
- invoke_result_t<_Fd&, _CallArgs...>
- operator()(_CallArgs&&... __call_args) &
- noexcept(is_nothrow_invocable_v<_Fd&, _CallArgs...>)
- { return std::invoke(_M_fd, std::forward<_CallArgs>(__call_args)...); }
-
- template<typename... _CallArgs>
- constexpr
- invoke_result_t<const _Fd&, _CallArgs...>
- operator()(_CallArgs&&... __call_args) const &
- noexcept(is_nothrow_invocable_v<const _Fd&, _CallArgs...>)
- { return std::invoke(_M_fd, std::forward<_CallArgs>(__call_args)...); }
-
- template<typename... _CallArgs>
- constexpr
- invoke_result_t<_Fd, _CallArgs...>
- operator()(_CallArgs&&... __call_args) &&
- noexcept(is_nothrow_invocable_v<_Fd, _CallArgs...>)
- {
- return std::invoke(std::move(_M_fd),
- std::forward<_CallArgs>(__call_args)...);
- }
-
- template<typename... _CallArgs>
- constexpr
- invoke_result_t<const _Fd, _CallArgs...>
- operator()(_CallArgs&&... __call_args) const &&
- noexcept(is_nothrow_invocable_v<const _Fd, _CallArgs...>)
- {
- return std::invoke(std::move(_M_fd),
- std::forward<_CallArgs>(__call_args)...);
- }
-
- private:
- [[no_unique_address]] _Fd _M_fd;
- };
-
template<typename _Fn, typename... _Args>
- using _Bind_front_t
- = __conditional_t<sizeof...(_Args) == 0, _Bind_front0<decay_t<_Fn>>,
- _Bind_front<decay_t<_Fn>, decay_t<_Args>...>>;
+ using _Bind_front_t = _Bind_front<decay_t<_Fn>, decay_t<_Args>...>;
/** Create call wrapper by partial application of arguments to function.
*
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