fix Core crash when cancelling server timers

[Sonitex 1099]

When cancelling server timers a core will crash as it is removing a timer from the map and increasing the iterator twice by calling erase() function and afterwards increasing it once again when entering a new cycle of loop. One way of solving this issue is to first collect the timers which must be removed and clean them up at the end. You can also add a simple counter which is increased at each end of the loop's cycle and remove the timer directly from the first loop by specifying the position with the counter itself.

 

Note that this issue seems to appear after upgrading code to C++11 or higher.

 

Replace the following function inside questmanager.cpp:

	void CQuestManager::CancelServerTimers(DWORD arg)
	{
		vector<pair<string, DWORD>> ServerTimersToDelete;

		for (const auto& kv : m_mapServerTimer) {
			if (kv.first.second == arg) {
				LPEVENT event = kv.second;
				event_cancel(&event);
				ServerTimersToDelete.push_back(kv.first);
			}
		}

		// Delete all the required server timers
		for (const auto &timer : ServerTimersToDelete)
			m_mapServerTimer.erase(timer);

		// Clean up
		ServerTimersToDelete.clear();
	}

 

Edited December 20, 2020 by Sonitex

[Mali 20208]

thanks for fix

For me, I wouldn't prefer this. Because you are copying pair. Just use simple iterator like this:

for ( ; it != container.end(); ) {
	if (condition)
		it = container.erase(it);
	else
		++it;
}

 

[Sonitex 1099]

17 minutes ago, Mali61 said:

thanks for fix

For me, I wouldn't prefer this. Because you are copying pair. Just use simple iterator like this:

for ( ; it != container.end(); ) {
	if (condition)
		it = container.erase(it);
	else
		++it;
}

 

 

That is the other way I was talking about and you are right, this is much more efficient way of doing it as we are not copying elements to another vector and cleaning them up afterwards. Thank you for the code

[Hysteria 8]

this is the best fix if someone need it

	void CQuestManager::CancelServerTimers(DWORD arg)
	{
		itertype(m_mapServerTimer) it = m_mapServerTimer.begin();
   
		for (; it != m_mapServerTimer.end(); )
		{
			if (it->first.second == arg)
			{
				LPEVENT event = it->second;
				event_cancel(&event);
				m_mapServerTimer.erase(it++);
			}
			else
				++it;
		}
	}

 

[martysama0134 4714]

I know this is an old thread. This should solve it:

On 12/20/2020 at 4:47 PM, Mali said:

thanks for fix

For me, I wouldn't prefer this. Because you are copying pair. Just use simple iterator like this:

for ( ; it != container.end(); ) {
	if (condition)
		it = container.erase(it);
	else
		++it;
}

 

The return value of .erase must be stored in the it again.

To be more precise:

	void CQuestManager::CancelServerTimers(DWORD arg)
	{
		auto it = m_mapServerTimer.begin();
		while (it != m_mapServerTimer.end()) {
			if (it->first.second == arg) {
				event_cancel(&it->second);
				it = m_mapServerTimer.erase(it);
				continue;
			}
			++it;
		}
	}

if you're edgy:

	void CQuestManager::CancelServerTimers(DWORD arg)
	{
		for (auto it = m_mapServerTimer.begin(); it != m_mapServerTimer.end();) {
			if (it->first.second == arg) {
				event_cancel(&it->second);
				it = m_mapServerTimer.erase(it);
			} else
				++it;
		}
	}

or in c++20

void CancelServerTimers(uint32_t arg) {
    auto erase_check = [&](auto&& it) {
        if (it.first.second == arg) {
            auto event = it.second; // copy ptr
            event_cancel(&event);
        }
        return it.first.second == arg;
    };
    std::erase_if(m_mapServerTimer, erase_check);
}

https://godbolt.org/z/EEa5Yz7Mn

 

Edited December 23, 2022 by martysama0134