小编Jou*_*uny的帖子

在学习多线程编程时，我编写了以下代码。

#include <thread>
#include <iostream>
#include <cassert>

void check() {
    int a = 0;
    int b = 0;
    {
        std::jthread t2([&](){
            int i = 0;
            while (a >= b) {
                ++i;
            }
            std::cout << "failed at iteration " << i << "\n"
                      // I know at this point a and b may have changed
                      << a << " >= " << b << "\n";
            std::exit(0);
        });
        std::jthread t1([&](){
            while (true) {
                ++a;
                ++b;
            }
        });
    }
}

int main() { …

为什么编译器在不需要副本构造函数时会关心它？

#include <iostream>

template<typename T>
void print(T);

class Foo {
    Foo(const Foo&);
public:
    Foo(){}

};

template<>
void print(const Foo& f) {
    std::cout << "Foo\n";
}


int main(){
    Foo foo;
    print(foo);
}

函数print已重载以接受，const Foo&但编译器会产生以下编译错误：

main.cpp: In function ‘int main()’:
main.cpp:21:14: error: ‘Foo::Foo(const Foo&)’ is private within this context
   21 |     print(foo);
      |              ^
main.cpp:7:5: note: declared private here
    7 |     Foo(const Foo&);
      |     ^~~
main.cpp:4:12: note:   initializing argument 1 of ‘void print(T) [with T = Foo]’
    4 …