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/*
* Copyright (C) 2019 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.
*
*/
#include "config.h"
#include <wtf/RefCounted.h>
#include <wtf/StackShot.h>
#include <wtf/ThreadSafeRefCounted.h>
namespace WTF {
bool RefCountedBase::areThreadingChecksEnabledGlobally { false };
static_assert(sizeof(RefCountedBase) == sizeof(ThreadSafeRefCountedBase));
class RefLogStackShot : public StackShot {
static const size_t s_size = 18;
static const size_t s_skip = 6;
public:
RefLogStackShot(const void* ptr)
: StackShot(s_size)
, m_ptr(ptr)
{
}
const void* ptr() { return m_ptr; }
void print()
{
if (size() < s_skip)
return;
WTFPrintBacktrace(span().subspan(s_skip));
}
private:
const void* m_ptr;
};
class RefLogSingleton {
public:
static void append(const void* ptr)
{
RefLogStackShot* stackShot = new RefLogStackShot(ptr);
size_t index = s_end.fetch_add(1, std::memory_order_acquire) & s_sizeMask;
if (RefLogStackShot* old = s_buffer[index].exchange(nullptr, std::memory_order_acquire))
delete old;
// Other threads may have raced ahead and filled the log. If so, our stack shot is oldest, so we drop it.
RefLogStackShot* expected = nullptr;
if (!s_buffer[index].compare_exchange_strong(expected, stackShot, std::memory_order_release))
delete stackShot;
}
template<typename Callback>
static void forEachLIFO(const Callback& callback)
{
size_t last = s_end.load(std::memory_order_acquire) - 1;
for (size_t i = 0; i < s_size; ++i) {
size_t index = (last - i) & s_sizeMask;
RefLogStackShot* stackShot = s_buffer[index].load(std::memory_order_acquire);
if (!stackShot)
continue;
callback(stackShot);
}
}
private:
static constexpr size_t s_size = 512; // Keep the log short to decrease the odds of logging a previous alias at the same address.
static constexpr size_t s_sizeMask = s_size - 1;
static std::atomic<size_t> s_end;
static std::array<std::atomic<RefLogStackShot*>, s_size> s_buffer;
};
std::atomic<size_t> RefLogSingleton::s_end;
std::array<std::atomic<RefLogStackShot*>, RefLogSingleton::s_size> RefLogSingleton::s_buffer;
void RefCountedBase::logRefDuringDestruction(const void* ptr)
{
RefLogSingleton::append(ptr);
}
void RefCountedBase::printRefDuringDestructionLogAndCrash(const void* ptr)
{
WTFLogAlways("Error: Dangling RefPtr: %p", ptr);
WTFLogAlways("This means that a ref() during destruction was not balanced by a deref() before destruction ended.");
WTFLogAlways("Below are the most recent ref()'s during destruction for this address.");
RefLogSingleton::forEachLIFO([&] (RefLogStackShot* stackShot) {
if (stackShot->ptr() != ptr)
return;
WTFLogAlways(" ");
stackShot->print();
});
CRASH_WITH_SECURITY_IMPLICATION();
}
}
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