C++ PTHREADS - Invalid conversion void*(*)() to void*(*)(void*) - c++

Question

I have to send the parameter "r" of type "risposta" to the function RispostaServer. The compiler gives me: invalid conversion void*(*)() to void*(*)(void*)
Here's the code fragment that i should correct:
{/*other istructions*/
risposta r;
r.mess = m1;
r.codaSC = codaSC;
pthread_create(&threads[threads_index],&attr,RispostaServer,(void*)&r);
threads_index++;
}
void* RispostaServer(void* m){
risposta* m1 = (risposta*) m;
/*other istructions*/
}
What should i edit ? I'm trying it by hours.

Answer 1

I'll take a stab in the dark at this, pre-[MCVE] (but please do provide one).
Does your declaration for RispostaServer look like this?
void* RispostaServer();
Then the only version of RispostaServer visible to the pthread_create call is one that doesn't take an argument. That matches the type complaint kicked out by the compiler.
Your later function definition creates a new overload of RispostaServer that does take an argument, and you'd be able to call that lower down the code, but it's too late for the pthread_create call by then.
The declaration should match the definition:
// Entrypoint for Risposta worker thread.
// Argument must be a risposta*, cast to `void*`.
void* RispostaServer(void* m);
By the way, your thread will be broken because you're passing in a pointer to a local variable that immediately goes out of scope, so add the following comment to the above:
// The risposta it points to must exist for the lifetime
// of the thread.
…and you really ought to be using std::thread rather than the C API of a platform-specific library.