实现一个简单的C++线程池,main函数中enqueue函数使用时提示无匹配的函数模板实例,这是为什么呢?用的C++20标准。
报错截图在最后。
#include <iostream>
#include <vector>
#include <list>
#include <shared_mutex>
#include <atomic>
#include <functional>
#include <iostream>
#include <vector>
#include <queue>
#include <thread>
#include <mutex>
#include <condition_variable>
#include <functional>
#include <future>
#include <atomic>
#include <type_traits>
class ThreadPool {
std::vector<std::thread> workers;
std::queue<std::function<void()>> tasks;
std::mutex queueMutex;
std::condition_variable condition;
std::atomic<bool> stop;
public:
explicit ThreadPool(size_t numThreads) : stop(false) {
for (size_t i = 0; i < numThreads; ++i) {
workers.emplace_back([this] {
while (true) {
std::function<void()> task;
{
std::unique_lock<std::mutex> lock(this->queueMutex);
this->condition.wait(lock, [this]() { return this->stop || !this->tasks.empty(); });
if (this->stop && this->tasks.empty()) {
return;
}
task = std::move(this->tasks.front());
this->tasks.pop();
}
task();
}
});
}
}
ThreadPool (const ThreadPool&) = delete;
ThreadPool& operator=(const ThreadPool&) = delete;
template <class F, class... Args>
auto enqueue(F&& f, Args&&... args) -> std::future<typename std::invoke_result<F(Args...)>::type> {
using returnType = typename std::invoke_result<F(Args...)>::type;
auto task = std::make_shared<std::packaged_task<returnType()>>(
std::bind(std::forward<F>(f), std::forward<Args>(args)...)
);
std::future<returnType> res = task->get_future();
{
std::unique_lock<std::mutex> lock(queueMutex);
if (stop) {
throw std::runtime_error("enqueue on stopped ThreadPool");
}
tasks.emplace([task]() { return (*task)(); });
}
condition.notify_one();
return res;
}
~ThreadPool() {
{
std::unique_lock<std::mutex> lock(queueMutex);
stop = true;
}
condition.notify_all();
for (std::thread& worker : workers) {
worker.join();
}
}
};
int main() {
ThreadPool pool(4);
auto result1 = pool.enqueue([](int a, int b) { return a + b; }, 5, 3);
auto result2 = pool.enqueue([] { std::cout << "Hello from the thread pool!\n"; });
std::cout << "Result of addition: " << result1.get() << std::endl;
return 0;
}