Useless parallel stack allocator in C++

alloc_task.cpp

#include <cstring>
#include <iostream>
#include <thread>
#include <future>
#include <queue>

std::mutex mqMutex;
std::queue<std::tuple<size_t, std::promise<void*>&>> mq;

void * alloc(size_t len) {
	std::promise<void*> p;

	{
		std::lock_guard<std::mutex> lock(mqMutex);
		mq.emplace(len, p);
	}

	std::future<void*> future = p.get_future();
	future.wait();

	return future.get();
}

void alloc_task() {
	while(true) {
		// should wait for some flag to be triggered here really
		std::lock_guard<std::mutex> lock(mqMutex);

		if(!mq.empty()) {
			auto rp = mq.front();
			mq.pop();
			void *ptr = alloca(std::get<0>(rp));
			std::get<1>(rp).set_value(ptr);
		}
	}
}

int main() {
	std::thread task {alloc_task};
	task.detach();

	char *buffer = (char *) alloc(4);
	strcpy(buffer, "lol");

	char *buffer2 = (char *) alloc(4);
	strcpy(buffer2, "abc");

	std::cout << buffer << std::endl;
	std::cout << buffer2 << std::endl;

	return 0;
}