libstdc++: Fix type-erasure in experimental::net::executor (PR 94203)

The _Tgt and _TgtImpl types that implement type-erasure didn't agree on
the virtual interface, so failed as soon as they were instantiated. With
Clang they failed even sooner. The interface was also dependent on
whether RTTI was enabled or not.

This patch fixes the broken virtual functions and makes the type work
without RTTI, by using a pointer to a specialization of a function
template (similar to the approaches in std::function and std::any).

The changes to the virtual functions would be an ABI change, except that
the previous code didn't even compile if instantiated. This is
experimental TS material anyway.

	PR libstdc++/94203
	* include/experimental/executor (executor::executor(Executor)): Call
	make_shared directly instead of _M_create. Create _Tgt1 object.
	(executor::executor(allocator_arg_t, const ProtoAlloc&, Executor)):
	Call allocate_shared directly instead of _M_create. Create _Tgt2
	object.
	(executor::target_type): Add cast needed for new _Tgt interface.
	(executor::target): Define when RTTI is disabled. Use _Tgt::_M_func.
	(executor::_Tgt): Define the same interface whether RTTI is enabled or
	not.
	(executor::_Tgt::target_type, executor::_Tgt::target): Do not use
	std::type_info in the interface.
	(executor::_Tgt::_M_func): Add data member.
	(executor::_TgtImpl): Replace with _Tgt1 and _Tgt2 class templates.
	(executor::_Tgt1::_S_func): Define function to access target without
	depending on RTTI.
	(executor::_M_create): Remove.
	(operator==, operator!=): Simplify comparisons for executor.
	* include/experimental/socket (is_error_code_enum<socket_errc>):
	Define specialization before use.
	* testsuite/experimental/net/executor/1.cc: New test.
This commit is contained in:
Jonathan Wakely 2020-03-18 00:23:39 +00:00
parent 3b2cc34369
commit 98f29f5638
4 changed files with 287 additions and 80 deletions

View File

@ -1,3 +1,27 @@
2020-03-18 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/94203
* include/experimental/executor (executor::executor(Executor)): Call
make_shared directly instead of _M_create. Create _Tgt1 object.
(executor::executor(allocator_arg_t, const ProtoAlloc&, Executor)):
Call allocate_shared directly instead of _M_create. Create _Tgt2
object.
(executor::target_type): Add cast needed for new _Tgt interface.
(executor::target): Define when RTTI is disabled. Use _Tgt::_M_func.
(executor::_Tgt): Define the same interface whether RTTI is enabled or
not.
(executor::_Tgt::target_type, executor::_Tgt::target): Do not use
std::type_info in the interface.
(executor::_Tgt::_M_func): Add data member.
(executor::_TgtImpl): Replace with _Tgt1 and _Tgt2 class templates.
(executor::_Tgt1::_S_func): Define function to access target without
depending on RTTI.
(executor::_M_create): Remove.
(operator==, operator!=): Simplify comparisons for executor.
* include/experimental/socket (is_error_code_enum<socket_errc>):
Define specialization before use.
* testsuite/experimental/net/executor/1.cc: New test.
2020-03-16 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/94199

View File

@ -295,26 +295,22 @@ inline namespace v1
class executor;
bool
operator==(const executor& __a, const executor& __b) noexcept;
operator==(const executor&, const executor&) noexcept;
bool
operator==(const executor& __e, nullptr_t) noexcept;
operator==(const executor&, nullptr_t) noexcept;
inline bool
operator==(nullptr_t, const executor& __e) noexcept
{ return __e == nullptr; }
bool
operator==(nullptr_t, const executor&) noexcept;
inline bool
operator!=(const executor& __a, const executor& __b) noexcept
{ return !(__a == __b); }
bool
operator!=(const executor&, const executor&) noexcept;
inline bool
operator!=(const executor& __e, nullptr_t) noexcept
{ return !(__e == nullptr); }
bool
operator!=(const executor&, nullptr_t) noexcept;
inline bool
operator!=(nullptr_t, const executor& __e) noexcept
{ return !(__e == nullptr); }
bool
operator!=(nullptr_t, const executor&) noexcept;
void swap(executor&, executor&) noexcept;
@ -999,12 +995,13 @@ inline namespace v1
template<typename _Executor>
executor(_Executor __e)
: _M_target(_M_create(std::move(__e)))
: _M_target(make_shared<_Tgt1<_Executor>>(std::move(__e)))
{ }
template<typename _Executor, typename _ProtoAlloc>
executor(allocator_arg_t, const _ProtoAlloc& __a, _Executor __e)
: _M_target(_M_create(std::move(__e), __a))
: _M_target(allocate_shared<_Tgt2<_Executor, _ProtoAlloc>>(__a,
std::move(__e), __a))
{ }
executor& operator=(const executor&) noexcept = default;
@ -1101,28 +1098,46 @@ inline namespace v1
#if __cpp_rtti
const type_info&
target_type() const noexcept
{ return _M_target ? _M_target->target_type() : typeid(void); }
{
if (_M_target)
return *static_cast<const type_info*>(_M_target->target_type());
return typeid(void);
}
#endif
template<typename _Executor>
_Executor*
target() noexcept
{
void* __p = nullptr;
if (_M_target)
if (const auto* __p = _M_target->target(typeid(_Executor)))
return const_cast<_Executor*>(static_cast<const _Executor>(__p));
return nullptr;
{
if (_M_target->_M_func == &_Tgt1<remove_cv_t<_Executor>>::_S_func)
__p = _M_target->_M_func(_M_target.get(), nullptr);
#if __cpp_rtti
else
__p = _M_target->target(&typeid(_Executor));
#endif
}
return static_cast<_Executor*>(__p);
}
template<typename _Executor>
const _Executor*
target() const noexcept
{
const void* __p = nullptr;
if (_M_target)
if (const auto* __p = _M_target->target(typeid(_Executor)))
return static_cast<const _Executor*>(__p);
return nullptr;
}
{
if (_M_target->_M_func == &_Tgt1<remove_cv_t<_Executor>>::_S_func)
return (_Executor*)_M_target->_M_func(_M_target.get(), nullptr);
#if __cpp_rtti
else
__p = _M_target->target(&typeid(_Executor));
#endif
}
return static_cast<const _Executor*>(__p);
}
private:
struct _Tgt
@ -1133,85 +1148,134 @@ inline namespace v1
virtual void dispatch(std::function<void()>) const = 0;
virtual void post(std::function<void()>) const = 0;
virtual void defer(std::function<void()>) const = 0;
#if __cpp_rtti
virtual const type_info& target_type() const = 0;
virtual void* target(const std::type_info&) const = 0;
virtual const void* target_type() const noexcept = 0;
virtual void* target(const void*) noexcept = 0;
virtual bool _M_equals(_Tgt*) const noexcept = 0;
virtual const void* _M_get_executor() const noexcept = 0;
#endif
using _Func = void* (_Tgt*, const _Tgt*);
_Func* _M_func; // Provides access to target without RTTI
};
template<typename _Ex, typename _Alloc>
struct _TgtImpl : _Tgt
template<typename _Ex>
struct _Tgt1 : _Tgt
{
explicit
_TgtImpl(_Ex&& __ex, const _Alloc& __a)
: _M_impl(std::move(__ex), __a) { }
_Tgt1(_Ex&& __ex)
: _M_ex(std::move(__ex))
{ this->_M_func = &_S_func; }
void on_work_started() const noexcept { _M_ex().on_work_started(); }
void on_work_finished() const noexcept { _M_ex().on_work_finished(); }
execution_context& context() const noexcept { return _M_ex().context(); }
void
dispatch(std::function<void()> __f) const
{ _M_ex().dispatch(std::move(__f), _M_alloc()); }
void
post(std::function<void()> __f) const
{ _M_ex().post(std::move(__f), _M_alloc()); }
void
defer(std::function<void()> __f) const
{ _M_ex().defer(std::move(__f), _M_alloc()); }
on_work_started() const noexcept override
{ _M_ex.on_work_started(); }
#if __cpp_rtti
virtual const type_info&
target_type() const
{ return typeid(_Ex); }
void
on_work_finished() const noexcept override
{ _M_ex.on_work_finished(); }
virtual const void*
target(const std::type_info& __ti) const
execution_context&
context() const noexcept override
{ return _M_ex.context(); }
void
dispatch(std::function<void()> __f) const override
{ _M_ex.dispatch(std::move(__f), allocator<void>()); }
void
post(std::function<void()> __f) const override
{ _M_ex.post(std::move(__f), allocator<void>()); }
void
defer(std::function<void()> __f) const override
{ _M_ex.defer(std::move(__f), allocator<void>()); }
const void*
target_type() const noexcept override
{
if (__ti == typeid(_Ex))
return std::addressof(_M_ex());
#if __cpp_rtti
return &typeid(_Ex);
#else
return nullptr;
#endif
}
void*
target(const void* __ti) noexcept override
{
#if __cpp_rtti
if (*static_cast<const type_info*>(__ti) == typeid(_Ex))
return std::__addressof(_M_ex);
#endif
return nullptr;
}
virtual bool
_M_equals(const _Tgt* __tgt) const noexcept
bool
_M_equals(_Tgt* __tgt) const noexcept override
{
if (__tgt->target_type() == typeid(_Ex))
*static_cast<const _Ex*>(__tgt->_M_get_executor()) == _M_ex();
#if __cpp_rtti
if (const void* __p = __tgt->target(&typeid(_Ex)))
return *static_cast<const _Ex*>(__p) == _M_ex;
#endif
return false;
}
virtual const void*
_M_get_executor() const noexcept
{ return std::addressof(_M_ex()); }
#endif
_Ex _M_ex [[__no_unique_address__]];
_Ex& _M_ex() { return std::get<0>(_M_impl); }
_Alloc& _M_alloc() { return std::get<1>(_M_impl); }
std::tuple<_Ex, _Alloc> _M_impl;
static void*
_S_func(_Tgt* __p, const _Tgt* __q) noexcept
{
auto& __ex = static_cast<_Tgt1*>(__p)->_M_ex;
if (__q)
{
if (__ex == static_cast<const _Tgt1*>(__q)->_M_ex)
return __p;
else
return nullptr;
}
else
return std::__addressof(__ex);
}
};
template<typename _Ex, typename _Alloc = std::allocator<void>>
shared_ptr<_Tgt>
_M_create(_Ex&& __ex, const _Alloc& __a = _Alloc())
template<typename _Ex, typename _Alloc>
struct _Tgt2 : _Tgt1<_Ex>
{
return allocate_shared<_TgtImpl<_Ex, _Alloc>>(__a, std::move(__ex),
__a);
}
explicit
_Tgt2(_Ex&& __ex, const _Alloc& __a)
: _Tgt1<_Ex>(std::move(__ex)), _M_alloc(__a) { }
void
dispatch(std::function<void()> __f) const override
{ this->_M_ex.dispatch(std::move(__f), _M_alloc); }
void
post(std::function<void()> __f) const override
{ this->_M_ex.post(std::move(__f), _M_alloc); }
void
defer(std::function<void()> __f) const override
{ this->_M_ex.defer(std::move(__f), _M_alloc); }
_Alloc _M_alloc [[__no_unique_address__]];
};
// Partial specialization for std::allocator<T>.
// Don't store the allocator.
template<typename _Ex, typename _Tp>
struct _Tgt2<_Ex, std::allocator<_Tp>> : _Tgt1<_Ex>
{ };
friend bool
operator==(const executor& __a, const executor& __b) noexcept
{
if (__a._M_target == __b._M_target)
_Tgt* __ta = __a._M_target.get();
_Tgt* __tb = __b._M_target.get();
if (__ta == __tb)
return true;
if (!__a._M_target || !__b._M_target)
if (!__ta || !__tb)
return false;
#if __cpp_rtti
return __a._M_target->_M_equals(__b._M_target.get());
#else
return false; // XXX can we do better?
#endif
if (__ta->_M_func == __tb->_M_func)
return __ta->_M_func(__ta, __tb);
return __ta->_M_equals(__tb);
}
shared_ptr<_Tgt> _M_target;
@ -1224,6 +1288,22 @@ inline namespace v1
operator==(const executor& __e, nullptr_t) noexcept
{ return !__e; }
inline bool
operator==(nullptr_t, const executor& __e) noexcept
{ return !__e; }
inline bool
operator!=(const executor& __a, const executor& __b) noexcept
{ return !(__a == __b); }
inline bool
operator!=(const executor& __e, nullptr_t) noexcept
{ return (bool)__e; }
inline bool
operator!=(nullptr_t, const executor& __e) noexcept
{ return (bool)__e; }
/// Swap two executor objects.
inline void swap(executor& __a, executor& __b) noexcept { __a.swap(__b); }

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@ -79,6 +79,20 @@ inline namespace v1
not_found = 4
};
} // namespace v1
} // namespace net
} // namespace experimental
template<>
struct is_error_code_enum<experimental::net::v1::socket_errc>
: public true_type {};
namespace experimental
{
namespace net
{
inline namespace v1
{
const error_category& socket_category() noexcept
{
struct __cat : error_category
@ -2602,10 +2616,6 @@ inline namespace v1
} // namespace net
} // namespace experimental
template<>
struct is_error_code_enum<experimental::net::v1::socket_errc>
: public true_type {};
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

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@ -0,0 +1,93 @@
// Copyright (C) 2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
// { dg-do run { target c++14 } }
#include <experimental/executor>
#include <testsuite_hooks.h>
namespace net = std::experimental::net;
void
test01()
{
net::executor e;
VERIFY( !e );
VERIFY( e == nullptr );
VERIFY( nullptr == e );
VERIFY( e == e );
VERIFY( e == e );
net::executor e2;
VERIFY( e == e2 );
swap(e, e2);
VERIFY( e == e2 );
e = e2;
VERIFY( e == e2 );
}
void
test02()
{
struct E
{
void on_work_started() const noexcept { }
void on_work_finished() const noexcept { }
net::execution_context& context() const noexcept { return c; }
void dispatch(std::function<void()>, std::allocator<void>) const { }
void post(std::function<void()>, std::allocator<void>) const { }
void defer(std::function<void()>, std::allocator<void>) const { }
net::execution_context& c;
bool operator==(const E& rhs) const noexcept
{ return &c == &rhs.c; }
};
net::execution_context c;
E d{c};
net::executor e(d);
VERIFY( e == e );
VERIFY( e != nullptr );
VERIFY( nullptr != e );
VERIFY( &e.context() == &c );
#if __cpp_rtti
VERIFY( e.target_type() == typeid(E) );
#endif
VERIFY( *e.target<E>() == d );
VERIFY( *e.target<const E>() == d );
VERIFY( *const_cast<const net::executor&>(e).target<E>() == d );
VERIFY( *const_cast<const net::executor&>(e).target<const E>() == d );
net::executor f = e;
VERIFY( f == e );
e = nullptr;
VERIFY( f != e );
swap(e, f);
VERIFY( f == nullptr );
VERIFY( nullptr != e );
net::executor g(E{c});
VERIFY( e == g );
}
int
main()
{
test01();
test02();
}