Error: expected ‘)’ before ‘*’ token despite not include-loop - c++

Question

I have a class RenderMachine which includes RenderObject and vice versa. I know there have been tons of questions about this error, but the solution for this doesn't do anything.
They say the error is mostly because a include-loop but I don't have one because in the RenderObject header I only allocate memory for a pointer to RenderMachine and vice versa.
RenderObject.h
#pragma once
#include "RenderMachine.h"
class RenderObject
{
public:
RenderObject(RenderMachine* rm){}
};
RenderMachine.h
#pragma once
#include "RenderObject.h"
class RenderMachine
{
public:
void add(RenderObject* renderObject);
};
The exact error is
error: expected ‘)’ before ‘*’ token
RenderObject(RenderMachine* rm)
^
Edit:
#include "RenderMachine.h"
class RenderMachine;
class RenderObject : public sf::Drawable
{
private:
int renderId;
public:
RenderObject(RenderMachine* rm){ (*rm).add(*this); }
int getRenderId() const { return renderId; }
#include "RenderObject.h"
class RenderMachine
{
std::vector< std::vector<sf::Drawable*> > renderVector;
public:
void add(RenderObject* renderObject);
And RenderMachine.cpp
#include "RenderMachine.h"
void RenderMachine::add(RenderObject* renderObject)
{
renderVector[(*renderObject).getRenderId()].push_back(renderObject);
}

Answer 1

Your call to add in the constructor of RenderObject should be done when RenderMachine is known (when it's a complete type). This goes for all calls to an object of the other type that you now have in your header files. Like this:
// RenderObject.h
class RenderMachine;
class RenderObject {
public:
RenderObject(RenderMachine* rm);
};
// RenderMachine.h
class RenderObject;
class RenderMachine {
public:
void add(RenderObject* renderObject);
};
// RenderObject.cpp
RenderObject::RenderObject(RenderMachine* rm) {
rm->add(this);
}
// RenderMachine.cpp
void RenderMachine::add(RenderObject* ro) {
}

Answer 2

You have a classic chicken-and-egg problem. The compiler cannot parse one header without first parsing the other header, because the classes in the headers refer to each other.
The solution is to use a forward declaration like this:
#include "RenderMachine.h"
class RenderMachine; // forward declaration
class RenderObject
{
public:
RenderObject(RenderMachine* rm){}
};