error: static assertion failed: std::thread arguments [...] but the number of arguments is correct

Question

这是我的代码：

#include <atomic>
#include <thread>
#include <vector>

int num_of_threads = 4;

// Simple function for incrementing an atomic int
void work(std::atomic<int>& a) {
    for (int i = 0; i < 100000; i++) {
        a++;
    }
}

void test() {
    std::atomic<int> a;
    a = 0;

    std::vector<std::thread> threads;
    threads.reserve(num_of_threads);

    for (size_t i = 0; i < num_of_threads; i++) {
        threads.emplace_back(work, a); //<- here is the issue
    }

    for (auto& thread : threads) {
        thread.join();
    }
}

int main() {
    test();
}

但是我收到以下错误：

/usr/include/c++/10.2.0/thread:136:44: error: static assertion failed: std::thread arguments must be invocable after conversion to rvalues
136 |           typename decay<_Args>::type...>::value,

我也查了这个问题，但我确定我的参数数量是正确的。

Answer 1

当创建一个线程时，它的参数被复制，这导致线程函数将引用作为参数的问题。

您需要包装要作为引用传递的对象，使用 std::ref（或 std::cref 用于对常量的引用）：

threads.emplace_back(work, std::ref(a));

error: static assertion failed: std::thread arguments [...] but the number of arguments is correct

error: static assertion failed: std::thread arguments [...] but the number of arguments is correct

c++

multithreading

compiler-errors