Function for the thread within a class in C++ - c++

Question

I'm having troubles with creation of the function, that should handle new thread. When I create it outside of the class, everything works allright, but when I want to create it inside a class, I can't realize, how to call it.
I call the function with:
pthread_t thread;
pthread_create(&thread, NULL,
sendMessage, (void *) fd);
and the function itself looks like this:
void * sendMessage(void *threadid) {
string message;
const char * c;
char buffer[200];
int fd = (long) threadid;
while (true) {
cin >> message;
if (message == "exit") {
break;
}
c = message.c_str();
strncpy(buffer, c, sizeof ( buffer));
send(fd, buffer, strlen(buffer), 0);
}
}
but when I declare it within a class e.g. void * Client::sendMessage(void *threadid) , I can't even build it because I get main.cpp:90:37: error: argument of type ‘void* (Client::)(void*)’ does not match ‘void* (*)(void*)’ Does anybody have any idea, what can cause it and how to fix it?

Answer 1

Just a quick demonstration of how std::thread can quickly make all your woes disappear (by seemlessly integrating with std::bind style invocation):
#include <string>
#include <thread>
#include <memory>
void some_function(int i, std::string bla)
{
}
struct some_class
{
void some_member_function(double x) const
{
}
};
int main()
{
std::thread t1(&some_function, 42, "the answer");
std::thread t2;
{
some_class instance;
t2 = std::thread(&some_class::some_member_function,
std::ref(instance),
3.14159);
t2.join(); // need to join before `instance` goes out of scope
}
{
auto managed = std::make_shared<some_class>();
t2 = std::thread([managed]()
{
managed->some_member_function(3.14159);
});
// `managed` lives on
}
if (t1.joinable()) t1.join();
if (t2.joinable()) t2.join();
}