c++ - GCC 4.7.2:带有指向成员函数指针的 std::thread

Question

正在为this question写测试代码我发现下面的注释行无法在 GCC 4.7.2 上编译:

#include <thread>
#include <iostream>

struct S {
    void f() {
        std::cout << "Calling f()" << std::endl;
    }
};

int main()
{
    S s;
    // std::thread t(&S::f, s); // does not compile?
    std::thread t(&S::f, &s);
    t.join();
}

但 cppreference 似乎声称“this”参数可以等效地作为对象、对象引用或对象指针传递:

If f is pointer to a member function of class T, then it is called. The return value is ignored. Effectively, the following code is executed: (t1.*f)(t2, ..., tN) if the type of t1 is either T, reference to T or reference to type derived from T. ((*t1).*f)(t2, ..., tN) otherwise.

我实际上认为这听起来很糟糕，并且更喜欢 std::thread 只允许指针或引用语义而不是互换地接受它们，但考虑到它似乎应该如此，上面是GCC/libstdc++ 错误(或者我误解了 cppreference)？

Answer 1

好像今晚是GCC Bug Party :-)

开个玩笑，这肯定是一个错误。 My answer to the linked question实际上包含证明，但由于没有强调，我将在这里重复。

这就是 INVOKE 设施的方式，std::thread 的构造函数(参见链接的答案)的行为是在 C+ 中定义的+11 标准

Define INVOKE (f, t1, t2, ..., tN) as follows:

— (t1.*f)(t2, ..., tN) when f is a pointer to a member function of a class T and t1 is an object of type T or a reference to an object of type T or a reference to an object of a type derived from T;

— ((*t1).*f)(t2, ..., tN) when f is a pointer to a member function of a class T and t1 is not one of the types described in the previous item;

— t1.*f when N == 1 and f is a pointer to member data of a class T and t1 is an object of type T or a reference to an object of type T or a reference to an object of a type derived from T;

— (*t1).*f when N == 1 and f is a pointer to member data of a class T and t1 is not one of the types described in the previous item;

— f(t1, t2, ..., tN) in all other cases.

粗体字的句子有效地指定了这一行:

std::thread t(&S::f, s);

应该编译。因此，这属于错误。

此外，它确实在 GCC 4.8.0(测试版)和 Clang 3.2 上进行了行编译。