错误C2248：使用线程时出现奇怪的错误

Question

I get the following errors

Error 2 error C2248: 'std::thread::thread' : cannot access private member declared in class 'std::thread' c:\\dropbox\\prog\\c++\\ttest\\ttest\\main.cpp 11 1 ttest

Error 1 error C2248: 'std::mutex::mutex' : cannot access private member declared in class 'std::mutex' c:\\dropbox\\prog\\c++\\ttest\\ttest\\main.cpp 11 1 ttest

my code

#include <mutex>
#include <thread>

using namespace std;

struct Serverbas
{
    mutex mut;
    thread t;
};

struct LoginServer : Serverbas
{
    void start()
    {
       t = thread(&LoginServer::run, *this);
    }
    void run() {}
};

int main() {}

Answer 1

The problem is this line here:

t = thread( &LoginServer::run, *this);

By dereferencing this, you are telling the compiler that you want to pass a copy of this object to the thread function. But your class isn't copy constructible because it contains a std::mutex and std::thread (neither of which is copy constructible). The errors you're getting are because of the inaccessible copy constructors for those two classes.

To fix it, don't dereference the object. The code will probably be clearer if you use a lambda anyway, like so:

t = thread([this] { run(); });

Answer 2

t = thread( &LoginServer::run, *this);

That first argument to the member function run (implicit in direct calls) should be the this pointer, ie just this . Don't dereference it.

When you dereference it all hell breaks loose because your std::thread and std::mutex members prevent objects of your class type from being copyable — the copy constructors of these member objects are private / delete d and that is the error you are seeing.

So:

t = thread(&LoginServer::run, this);