Error of threads in C++ "static assertion failed" - c++

Question

I made a quick summary of a project i have,
in which I have two threads that should be able to read and write on a common variable (protected by a mutex in the real project.
I don't understand this error
the two threads are in theory launched by a main thread
this main thread is a function of the object whose role is to manage the sub threads of this object.
I d'ont know if this is possible
main.cpp
#include <thread>
#include "Object.h"
using namespace std;
int main(){
Object tmp;
tmp.ChangeSetting(42);
thread mainthread(&Object::MainTread, &tmp);
mainthread.join();
}
Object.h
#ifndef SRC_OBJECT_H_
#define SRC_OBJECT_H_
#include <thread>
#include <iostream>
using namespace std;
class Object {
private:
int stupidvalue;
void subThread1();
void subThread2();
public:
void MainTread();
void ChangeSetting(int psvalue);
Object();
virtual ~Object();
};
#endif /* SRC_OBJECT_H_ */
Object.cpp
#include "Object.h"
void Object::subThread1(){
cout << "subthread1";
}
void Object::subThread2(){
cout << "subthread2";
}
void Object::MainTread(){
thread tmp1(subThread1);
thread tmp2(subThread2);
tmp1.join();
tmp2.join();
}
Object::Object() {
stupidvalue = 0;
}
void Object::ChangeSetting(int psvalue){
stupidvalue = psvalue;
}
Object::~Object() {
}
and my error
Info: Internal Builder is used for build
g++ -O0 -g3 -Wall -c -fmessage-length=0 -o "src\\main.o" "..\\src\\main.cpp"
g++ -O0 -g3 -Wall -c -fmessage-length=0 -o "src\\Object.o" "..\\src\\Object.cpp"
In file included from ..\src\Object.h:5,
from ..\src\Object.cpp:2:
C:/msys64/mingw32/include/c++/10.2.0/thread: In instantiation of 'std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (Object::*)(); _Args = {}; <template-parameter-1-3> = void]':
..\src\Object.cpp:13:24: required from here
C:/msys64/mingw32/include/c++/10.2.0/thread:136:44: error: static assertion failed: std::thread arguments must be invocable after conversion to rvalues
136 | typename decay<_Args>::type...>::value,
| ^~~~~
10:26:25 Build Failed. 1 errors, 0 warnings. (took 1s.304ms)
I read that it could be a typing error, but there is no parameter.

Answer 1

subThread1 and subThread2 are also member functions. You need to use pointer-to-member-function syntax like you did in main()
void Object::MainTread(){
thread tmp1(&Object::subThread1, this);
thread tmp2(&Object::subThread2, this);
tmp1.join();
tmp2.join();
}
Or use lambdas like the other answer suggests.

Answer 2

You are passing non-static method without object itself:
thread tmp1(subThread1); //error: subThread() cannot be invoked without object
You could make a lambda:
// passing this to lambda ok solong the object itself outlives the lambda ...
// in your case ok because joining in place.
thread tmp1([this]() { this->subThread(); });
Otherwise if thread could outlive the object, you would normally make a shared pointer (this way the object would leave through the shared_pointer at least as long as thread itself):
thread tmp1([self=this->shared_from_this()]() { self->subThread(); });
For this to work, Object would need to inherit from std::enable_shared_from_this<Object>:
class Object : public std::enable_shared_from_this<Object> {...}