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/*
* Copyright (C) 2006, 2007, 2008, 2009, 2010, 2013, 2025 Apple Inc. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, 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
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
*/
#pragma once
#include <wtf/Assertions.h>
#include <wtf/Compiler.h>
#include <wtf/FastMalloc.h>
#include <wtf/MainThread.h>
#include <wtf/Noncopyable.h>
#include <wtf/SwiftBridging.h>
namespace WTF {
#if ASSERT_ENABLED || ENABLE(SECURITY_ASSERTIONS)
#define CHECK_REF_COUNTED_LIFECYCLE 1
#else
#define CHECK_REF_COUNTED_LIFECYCLE 0
#endif
enum class RefCountIsThreadSafe : bool { No, Yes };
// This class holds debugging code to share among refcounting classes.
class RefCountDebugger {
public:
WTF_EXPORT_PRIVATE static void logRefDuringDestruction(const void*);
WTF_EXPORT_PRIVATE static void printRefDuringDestructionLogAndCrash (const void*) NO_RETURN_DUE_TO_CRASH;
RefCountDebugger()
#if ASSERT_ENABLED
: m_isOwnedByMainThread(isMainThread())
#endif
{
}
~RefCountDebugger()
{
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(m_deletionHasBegun);
ASSERT(!m_adoptionIsRequired);
#endif
}
void willRef(unsigned refCount, RefCountIsThreadSafe isThreadSafe = RefCountIsThreadSafe::No) const
{
applyRefDerefThreadingCheck(refCount, isThreadSafe);
applyRefDuringDestructionCheck();
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(!m_adoptionIsRequired);
#endif
}
void adopted()
{
#if CHECK_REF_COUNTED_LIFECYCLE
m_adoptionIsRequired = false;
#endif
}
void relaxAdoptionRequirement()
{
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(m_adoptionIsRequired);
m_adoptionIsRequired = false;
#endif
}
// Unsafe precondition: The caller must ensure thread-safe access to this object,
// for example by using a mutex.
void disableThreadingChecks()
{
#if ASSERT_ENABLED
m_areThreadingChecksEnabled = false;
#endif
}
static void enableThreadingChecksGlobally()
{
#if ASSERT_ENABLED
areThreadingChecksEnabledGlobally = true;
#endif
}
void applyRefDuringDestructionCheck() const
{
#if CHECK_REF_COUNTED_LIFECYCLE
if (!m_deletionHasBegun)
return;
logRefDuringDestruction(this);
#endif
}
void applyRefDerefThreadingCheck(unsigned refCount, RefCountIsThreadSafe isThreadSafe = RefCountIsThreadSafe::No) const
{
UNUSED_PARAM(refCount);
UNUSED_PARAM(isThreadSafe);
#if ASSERT_ENABLED
if (isThreadSafe == RefCountIsThreadSafe::Yes)
return;
if (refCount == 1) {
// Likely an ownership transfer across threads that may be safe.
m_isOwnedByMainThread = isMainThread();
} else if (areThreadingChecksEnabledGlobally && m_areThreadingChecksEnabled) {
// If you hit this assertion, it means that the RefCounted object was ref/deref'd
// from both the main thread and another in a way that is likely concurrent and unsafe.
// Derive from ThreadSafeRefCounted and make sure the destructor is safe on threads
// that call deref, or ref/deref from a single thread.
ASSERT_WITH_MESSAGE(m_isOwnedByMainThread == isMainThread(), "Unsafe to ref/deref from different threads");
}
#endif
}
void willDestroy(unsigned refCount) const
{
UNUSED_PARAM(refCount);
#if CHECK_REF_COUNTED_LIFECYCLE
if (refCount == 1)
return;
printRefDuringDestructionLogAndCrash(this);
#endif
}
void willDelete() const
{
#if CHECK_REF_COUNTED_LIFECYCLE
m_deletionHasBegun = true;
#endif
}
void willDeref(unsigned refCount, RefCountIsThreadSafe isThreadSafe = RefCountIsThreadSafe::No) const
{
applyRefDerefThreadingCheck(refCount, isThreadSafe);
#if CHECK_REF_COUNTED_LIFECYCLE
ASSERT(!m_adoptionIsRequired);
#endif
ASSERT(refCount);
}
#if CHECK_REF_COUNTED_LIFECYCLE
bool deletionHasBegun() const
{
return m_deletionHasBegun;
}
#endif
private:
#if ASSERT_ENABLED
mutable bool m_isOwnedByMainThread;
bool m_areThreadingChecksEnabled { true };
#endif
WTF_EXPORT_PRIVATE static bool areThreadingChecksEnabledGlobally;
#if CHECK_REF_COUNTED_LIFECYCLE
mutable std::atomic<bool> m_deletionHasBegun { false };
mutable bool m_adoptionIsRequired { true };
#endif
};
} // namespace WTF
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