The _Bind_front and _Bind_back class templates are now merged into a single
_Binder implementation that accepts _Back as a template parameter. This makes
the bind_back implementation available in C++20 mode, allowing it to be used
for range adaptor closures.
With zero bound arguments, bind_back and bind_front have equivalent
functionality. Consequently, _Bind_back_t now produces the same type as
bind_front (_Binder<false, _Fd>). A simple copy of the functor cannot be
returned in this case, as it would visibly affect overload resolution
(see included test cases).
libstdc++-v3/ChangeLog:
* include/std/functional: (__Bound_arg_storage::_S_apply_front)
(__Bound_arg_storage::_S_apply_front): Merged into _S_apply.
(__Bound_arg_storage::_S_apply): Merged above, add _Back
template parameter.
(std::_Bind_front): Renamed to std::_Binder and add _Back
template parameter.
(std::_Binder): Renamed from std::_Bind_front.
(_Binder::_Result_t, _Binder::_S_noexcept_invoke): Define.
(_Binder::operator()): Use _Result_t and _S_noexcept_invoke.
(_Binder::_S_call): Handle zero args specially.
(std::_Bind_front_t, std::_Bind_back_t): Defined in terms
of _Binder.
(std::_Bind_back): Merged into _Binder.
* testsuite/20_util/function_objects/bind_back/1.cc: New tests.
* testsuite/20_util/function_objects/bind_front/1.cc: New tests.
---
Returning a copy of the functor for zero bound args, turned to not
really be viable approach, as it changes overload resolution.
This makes bind_front(f) and bind_back(f) to reuse same functor,
and make _Bind_back_t available in C++20, in preparation for _Partial
rework.
Tested on x86_64-linux locally. OK for trunk?
libstdc++-v3/include/std/functional | 172 +++++++-----------
.../20_util/function_objects/bind_back/1.cc | 16 +-
.../function_objects/bind_back/111327.cc | 3 +-
.../20_util/function_objects/bind_front/1.cc | 15 ++
.../function_objects/bind_front/111327.cc | 2 +-
5 files changed, 103 insertions(+), 105 deletions(-)
diff --git a/libstdc++-v3/include/std/functional
b/libstdc++-v3/include/std/functional
index b1cda87929d..4122e8f9988 100644
--- a/libstdc++-v3/include/std/functional
+++ b/libstdc++-v3/include/std/functional
@@ -921,9 +921,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
std::forward<_BoundArgs>(__args)...);
}
-#ifdef __cpp_lib_bind_front // C++ >= 20
+#if __cplusplus >= 202002L
template<size_t, typename _Tp>
- struct _Indexed_bound_arg
+ struct _Indexed_bound_arg
{
[[no_unique_address]] _Tp _M_val;
};
@@ -931,24 +931,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename... _IndexedArgs>
struct _Bound_arg_storage : _IndexedArgs...
{
- template<typename _Fd, typename _Self, typename... _CallArgs>
+ template<bool _Back, typename _Fd, typename _Self, typename... _CallArgs>
static constexpr
decltype(auto)
- _S_apply_front(_Fd&& __fd, _Self&& __self, _CallArgs&&... __call_args)
+ _S_apply(_Fd&& __fd, _Self&& __self, _CallArgs&&... __call_args)
{
- return std::invoke(std::forward<_Fd>(__fd),
- __like_t<_Self, _IndexedArgs>(__self)._M_val...,
- std::forward<_CallArgs>(__call_args)...);
- }
-
- template<typename _Fd, typename _Self, typename... _CallArgs>
- static constexpr
- decltype(auto)
- _S_apply_back(_Fd&& __fd, _Self&& __self, _CallArgs&&... __call_args)
- {
- return std::invoke(std::forward<_Fd>(__fd),
- std::forward<_CallArgs>(__call_args)...,
- __like_t<_Self, _IndexedArgs>(__self)._M_val...);
+ if constexpr (_Back)
+ return std::invoke(std::forward<_Fd>(__fd),
+ std::forward<_CallArgs>(__call_args)...,
+ __like_t<_Self, _IndexedArgs>(__self)._M_val...);
+ else
+ return std::invoke(std::forward<_Fd>(__fd),
+ __like_t<_Self, _IndexedArgs>(__self)._M_val...,
+ std::forward<_CallArgs>(__call_args)...);
}
};
@@ -970,9 +965,30 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
}
- template<typename _Fd, typename... _BoundArgs>
- struct _Bind_front
+ template<bool _Back, typename _Fd, typename... _BoundArgs>
+ class _Binder
{
+ template<typename _Self, typename... _CallArgs>
+ using _Result_t = __conditional_t<
+ _Back,
+ invoke_result<__like_t<_Self, _Fd>,
+ _CallArgs..., __like_t<_Self, _BoundArgs>...>,
+ invoke_result<__like_t<_Self, _Fd>,
+ __like_t<_Self, _BoundArgs>..., _CallArgs...>>::type;
+
+ template<typename _Self, typename... _CallArgs>
+ static consteval bool
+ _S_noexcept_invocable()
+ {
+ if constexpr (_Back)
+ return is_nothrow_invocable_v< __like_t<_Self, _Fd>,
+ _CallArgs..., __like_t<_Self, _BoundArgs>...>;
+ else
+ return is_nothrow_invocable_v<__like_t<_Self, _Fd>,
+ __like_t<_Self, _BoundArgs>..., _CallArgs...>;
+ }
+
+ public:
static_assert(is_move_constructible_v<_Fd>);
static_assert((is_move_constructible_v<_BoundArgs> && ...));
@@ -980,7 +996,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// instead of the copy/move constructor.
template<typename _Fn, typename... _Args>
explicit constexpr
- _Bind_front(int, _Fn&& __fn, _Args&&... __args)
+ _Binder(int, _Fn&& __fn, _Args&&... __args)
noexcept(__and_<is_nothrow_constructible<_Fd, _Fn>,
is_nothrow_constructible<_BoundArgs, _Args>...>::value)
: _M_fd(std::forward<_Fn>(__fn)),
@@ -989,43 +1005,37 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cpp_explicit_this_parameter
template<typename _Self, typename... _CallArgs>
- constexpr
- invoke_result_t<__like_t<_Self, _Fd>, __like_t<_Self, _BoundArgs>...,
_CallArgs...>
+ constexpr _Result_t<_Self, _CallArgs...>
operator()(this _Self&& __self, _CallArgs&&... __call_args)
- noexcept(is_nothrow_invocable_v<__like_t<_Self, _Fd>,
- __like_t<_Self, _BoundArgs>...,
_CallArgs...>)
+ noexcept(_S_noexcept_invocable<_Self, _CallArgs...>())
{
- return _S_call(__like_t<_Self, _Bind_front>(__self),
+ return _S_call(__like_t<_Self, _Binder>(__self),
std::forward<_CallArgs>(__call_args)...);
}
#else
template<typename... _CallArgs>
requires true
- constexpr
- invoke_result_t<_Fd&, _BoundArgs&..., _CallArgs...>
+ constexpr _Result_t<_Binder&, _CallArgs...>
operator()(_CallArgs&&... __call_args) &
- noexcept(is_nothrow_invocable_v<_Fd&, _BoundArgs&..., _CallArgs...>)
+ noexcept(_S_noexcept_invocable<_Binder&, _CallArgs...>())
{
return _S_call(*this, std::forward<_CallArgs>(__call_args)...);
}
template<typename... _CallArgs>
requires true
- constexpr
- invoke_result_t<const _Fd&, const _BoundArgs&..., _CallArgs...>
+ constexpr _Result_t<const _Binder&, _CallArgs...>
operator()(_CallArgs&&... __call_args) const &
- noexcept(is_nothrow_invocable_v<const _Fd&, const _BoundArgs&...,
- _CallArgs...>)
+ noexcept(_S_noexcept_invocable<const _Binder&, _CallArgs...>())
{
return _S_call(*this, std::forward<_CallArgs>(__call_args)...);
}
template<typename... _CallArgs>
requires true
- constexpr
- invoke_result_t<_Fd, _BoundArgs..., _CallArgs...>
+ constexpr _Result_t<_Binder&&, _CallArgs...>
operator()(_CallArgs&&... __call_args) &&
- noexcept(is_nothrow_invocable_v<_Fd, _BoundArgs..., _CallArgs...>)
+ noexcept(_S_noexcept_invocable<_Binder&&, _CallArgs...>())
{
return _S_call(std::move(*this),
std::forward<_CallArgs>(__call_args)...);
@@ -1033,11 +1043,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename... _CallArgs>
requires true
- constexpr
- invoke_result_t<const _Fd, const _BoundArgs..., _CallArgs...>
+ constexpr _Result_t<const _Binder&&, _CallArgs...>
operator()(_CallArgs&&... __call_args) const &&
- noexcept(is_nothrow_invocable_v<const _Fd, const _BoundArgs...,
- _CallArgs...>)
+ noexcept(_S_noexcept_invocable<const _Binder&&, _CallArgs...>())
{
return _S_call(std::move(*this),
std::forward<_CallArgs>(__call_args)...);
@@ -1066,15 +1074,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
decltype(auto)
_S_call(_Tp&& __g, _CallArgs&&... __call_args)
{
- if constexpr (sizeof...(_BoundArgs) == 1)
- return std::invoke(std::forward<_Tp>(__g)._M_fd,
- std::forward<_Tp>(__g)._M_bound_args,
- std::forward<_CallArgs>(__call_args)...);
- else
- return _BoundArgsStorage::_S_apply_front(
+ if constexpr (sizeof...(_BoundArgs) > 1)
+ return _BoundArgsStorage::template _S_apply<_Back>(
std::forward<_Tp>(__g)._M_fd,
std::forward<_Tp>(__g)._M_bound_args,
std::forward<_CallArgs>(__call_args)...);
+ else if constexpr (sizeof...(_BoundArgs) == 0)
+ return std::invoke(std::forward<_Tp>(__g)._M_fd,
+ std::forward<_CallArgs>(__call_args)...);
+ else if constexpr (_Back) // sizeof...(_BoundArgs) == 1
+ return std::invoke(std::forward<_Tp>(__g)._M_fd,
+ std::forward<_CallArgs>(__call_args)...,
+ std::forward<_Tp>(__g)._M_bound_args);
+ else // !_Back && sizeof...(_BoundArgs) == 1
+ return std::invoke(std::forward<_Tp>(__g)._M_fd,
+ std::forward<_Tp>(__g)._M_bound_args,
+ std::forward<_CallArgs>(__call_args)...);
+
}
[[no_unique_address]] _Fd _M_fd;
@@ -1082,8 +1098,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
};
template<typename _Fn, typename... _Args>
- using _Bind_front_t = _Bind_front<decay_t<_Fn>, decay_t<_Args>...>;
+ using _Bind_front_t = _Binder<false, decay_t<_Fn>, decay_t<_Args>...>;
+
+ // for zero bounds args behavior of bind_front and bind_back is the same,
+ // so reuse _Bind_front_t, i.e. _Binder<false, ...>
+ template<typename _Fn, typename... _Args>
+ using _Bind_back_t
+ = _Binder<(sizeof...(_Args) > 0), decay_t<_Fn>, decay_t<_Args>...>;
+#endif // __cplusplus >= 202002L
+#ifdef __cpp_lib_bind_front // C++ >= 20
/** Create call wrapper by partial application of arguments to function.
*
* The result of `std::bind_front(f, args...)` is a function object that
@@ -1105,62 +1129,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // __cpp_lib_bind_front
#ifdef __cpp_lib_bind_back // C++ >= 23
- template<typename _Fd, typename... _BoundArgs>
- struct _Bind_back
- {
- static_assert(is_move_constructible_v<_Fd>);
- static_assert((is_move_constructible_v<_BoundArgs> && ...));
-
- // First parameter is to ensure this constructor is never used
- // instead of the copy/move constructor.
- template<typename _Fn, typename... _Args>
- explicit constexpr
- _Bind_back(int, _Fn&& __fn, _Args&&... __args)
- noexcept(__and_<is_nothrow_constructible<_Fd, _Fn>,
- is_nothrow_constructible<_BoundArgs, _Args>...>::value)
- : _M_fd(std::forward<_Fn>(__fn)),
-
_M_bound_args(__make_bound_args<_BoundArgs...>(std::forward<_Args>(__args)...))
- { static_assert(sizeof...(_Args) == sizeof...(_BoundArgs)); }
-
- template<typename _Self, typename... _CallArgs>
- constexpr
- invoke_result_t<__like_t<_Self, _Fd>, _CallArgs..., __like_t<_Self,
_BoundArgs>...>
- operator()(this _Self&& __self, _CallArgs&&... __call_args)
- noexcept(is_nothrow_invocable_v<__like_t<_Self, _Fd>,
- _CallArgs..., __like_t<_Self,
_BoundArgs>...>)
- {
- return _S_call(__like_t<_Self, _Bind_back>(__self),
- std::forward<_CallArgs>(__call_args)...);
- }
-
- private:
- using _BoundArgsStorage
- // _BoundArgs are required to be move-constructible, so this is valid.
- =
decltype(__make_bound_args<_BoundArgs...>(std::declval<_BoundArgs>()...));
-
- template<typename _Tp, typename... _CallArgs>
- static constexpr
- decltype(auto)
- _S_call(_Tp&& __g, _CallArgs&&... __call_args)
- {
- if constexpr (sizeof...(_BoundArgs) == 1)
- return std::invoke(std::forward<_Tp>(__g)._M_fd,
- std::forward<_CallArgs>(__call_args)...,
- std::forward<_Tp>(__g)._M_bound_args);
- else
- return _BoundArgsStorage::_S_apply_back(
- std::forward<_Tp>(__g)._M_fd,
- std::forward<_Tp>(__g)._M_bound_args,
- std::forward<_CallArgs>(__call_args)...);
- }
-
- [[no_unique_address]] _Fd _M_fd;
- [[no_unique_address]] _BoundArgsStorage _M_bound_args;
- };
-
- template<typename _Fn, typename... _Args>
- using _Bind_back_t = _Bind_back<decay_t<_Fn>, decay_t<_Args>...>;
-
/** Create call wrapper by partial application of arguments to function.
*
* The result of `std::bind_back(f, args...)` is a function object that
diff --git a/libstdc++-v3/testsuite/20_util/function_objects/bind_back/1.cc
b/libstdc++-v3/testsuite/20_util/function_objects/bind_back/1.cc
index a31528fc755..7141be282c0 100644
--- a/libstdc++-v3/testsuite/20_util/function_objects/bind_back/1.cc
+++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_back/1.cc
@@ -57,7 +57,6 @@ test01()
decltype(bind_back(std::declval<const F&>(), std::declval<const int&>(),
std::declval<const float&>()))
>);
-
// Reference wrappers should be handled:
static_assert(!std::is_same_v<
decltype(bind_back(std::declval<F>(), std::declval<int&>())),
@@ -197,6 +196,21 @@ testCallArgs(Args... args)
VERIFY( q.as_const && q.as_lvalue );
q = cg(std::move(ci));
VERIFY( q.as_const && ! q.as_lvalue );
+
+ struct S
+ {
+ int operator()(long, long, Args...) const { return 1; }
+ int operator()(int, void*, Args...) const { return 2; }
+ };
+
+ S s;
+ // literal zero can be converted to any pointer, so (int, void*)
+ // is best candidate
+ VERIFY( s(0, 0, args...) == 2 );
+ // both arguments are bound to int&&, and no longer can be
+ // converted to pointer, (long, long) is only candidate
+ VERIFY( bind_back(s)(0, 0, args...) == 1 );
+ VERIFY( bind_back(s, args...)(0, 0) == 1 );
}
void
diff --git
a/libstdc++-v3/testsuite/20_util/function_objects/bind_back/111327.cc
b/libstdc++-v3/testsuite/20_util/function_objects/bind_back/111327.cc
index de3ae47e37f..8e7dacf80df 100644
--- a/libstdc++-v3/testsuite/20_util/function_objects/bind_back/111327.cc
+++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_back/111327.cc
@@ -50,4 +50,5 @@ int main() {
std::move(std::as_const(g2))();
}
-// { dg-error "no type named 'type' in 'struct std::invoke_result" "" { target
c++23 } 0 }
+// { dg-error "no type named 'type' in 'std::__conditional_t<false,
std::invoke_result<" "" { target c++23 } 0 }
+// { dg-error "no type named 'type' in 'std::__conditional_t<true,
std::invoke_result<" "" { target c++23 } 0 }
diff --git a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/1.cc
b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/1.cc
index ef28de8321b..93efb2efea4 100644
--- a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/1.cc
+++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/1.cc
@@ -196,6 +196,21 @@ testCallArgs(Args... args)
VERIFY( q.as_const && q.as_lvalue );
q = cg(std::move(ci));
VERIFY( q.as_const && ! q.as_lvalue );
+
+ struct S
+ {
+ int operator()(Args..., long, long) const { return 1; }
+ int operator()(Args..., int, void*) const { return 2; }
+ };
+
+ S s;
+ // literal zero can be converted to any pointer, so (int, void*)
+ // is best candidate
+ VERIFY( s(args..., 0, 0) == 2 );
+ // both arguments are bound to int&&, and no longer can be
+ // converted to pointer, (long, long) is only candidate
+ VERIFY( bind_front(s)(args..., 0, 0) == 1 );
+ VERIFY( bind_front(s, args...)(0, 0) == 1 );
}
void
diff --git
a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
index 6694322d67e..58832a61a7e 100644
--- a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
+++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/111327.cc
@@ -50,4 +50,4 @@ int main() {
std::move(std::as_const(g2))();
}
-// { dg-error "no type named 'type' in 'struct std::invoke_result" "" { target
c++23 } 0 }
+// { dg-error "no type named 'type' in 'std::__conditional_t<false,
std::invoke_result<" "" { target c++23 } 0 }
--
2.50.1
