mirror of
https://github.com/SerenityOS/serenity
synced 2024-07-22 18:46:18 +00:00
e6f907a155
Problem:
- Many constructors are defined as `{}` rather than using the ` =
default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
instead of requiring the caller to default construct. This violates
the C++ Core Guidelines suggestion to declare single-argument
constructors explicit
(https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).
Solution:
- Change default constructors to use the compiler-provided default
constructor.
- Remove implicit conversion operators from `nullptr_t` and change
usage to enforce type consistency without conversion.
131 lines
4.1 KiB
C++
131 lines
4.1 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/Atomic.h>
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#include <AK/Checked.h>
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#include <AK/Noncopyable.h>
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#include <AK/Platform.h>
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#include <AK/StdLibExtras.h>
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namespace AK {
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template<class T>
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constexpr auto call_will_be_destroyed_if_present(const T* object) -> decltype(const_cast<T*>(object)->will_be_destroyed(), TrueType {})
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{
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const_cast<T*>(object)->will_be_destroyed();
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return {};
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}
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constexpr auto call_will_be_destroyed_if_present(...) -> FalseType
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{
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return {};
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}
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template<class T>
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constexpr auto call_one_ref_left_if_present(const T* object) -> decltype(const_cast<T*>(object)->one_ref_left(), TrueType {})
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{
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const_cast<T*>(object)->one_ref_left();
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return {};
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}
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constexpr auto call_one_ref_left_if_present(...) -> FalseType
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{
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return {};
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}
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class RefCountedBase {
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AK_MAKE_NONCOPYABLE(RefCountedBase);
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AK_MAKE_NONMOVABLE(RefCountedBase);
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public:
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using RefCountType = unsigned int;
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using AllowOwnPtr = FalseType;
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ALWAYS_INLINE void ref() const
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{
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auto old_ref_count = m_ref_count.fetch_add(1, AK::MemoryOrder::memory_order_relaxed);
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ASSERT(old_ref_count > 0);
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ASSERT(!Checked<RefCountType>::addition_would_overflow(old_ref_count, 1));
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}
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[[nodiscard]] ALWAYS_INLINE bool try_ref() const
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{
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RefCountType expected = m_ref_count.load(AK::MemoryOrder::memory_order_relaxed);
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for (;;) {
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if (expected == 0)
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return false;
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ASSERT(!Checked<RefCountType>::addition_would_overflow(expected, 1));
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if (m_ref_count.compare_exchange_strong(expected, expected + 1, AK::MemoryOrder::memory_order_acquire))
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return true;
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}
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}
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ALWAYS_INLINE RefCountType ref_count() const
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{
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return m_ref_count.load(AK::MemoryOrder::memory_order_relaxed);
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}
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protected:
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RefCountedBase() = default;
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ALWAYS_INLINE ~RefCountedBase()
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{
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ASSERT(m_ref_count.load(AK::MemoryOrder::memory_order_relaxed) == 0);
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}
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ALWAYS_INLINE RefCountType deref_base() const
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{
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auto old_ref_count = m_ref_count.fetch_sub(1, AK::MemoryOrder::memory_order_acq_rel);
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ASSERT(old_ref_count > 0);
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return old_ref_count - 1;
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}
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mutable Atomic<RefCountType> m_ref_count { 1 };
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};
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template<typename T>
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class RefCounted : public RefCountedBase {
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public:
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bool unref() const
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{
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auto new_ref_count = deref_base();
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if (new_ref_count == 0) {
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call_will_be_destroyed_if_present(static_cast<const T*>(this));
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delete static_cast<const T*>(this);
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return true;
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} else if (new_ref_count == 1) {
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call_one_ref_left_if_present(static_cast<const T*>(this));
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}
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return false;
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}
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};
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}
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using AK::RefCounted;
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