Add support for C++ classes and dynamic memory allocation via new and delete

[Plastpase123]

What has been implemented

• Parser can now parse class definitions, which act like extended C-structs that may contain function definitions, as well as expressions using new and delete
• Classes are transformed into C-style structs, and member functions are transformed to operate on struct pointers
• Usage of new for primitive types are encoded directly as CHCs, and translated into helper functions for class types
• Usage of delete is translated to free for primitive types, and helper function calls for class types

Limitations

• User must define a constructor and destructor for each defined class
• User must invoke destructor explicitly to ensure that an object is properly destroyed
• Using new to create pointer-to-pointers might be buggy

Not implemented (A non-exhaustive list)

• Other special member functions (move/copy constructors etc)
• Inheritance
• Dynamic dispatch
• Friend functions
• Function overloading

Examples

For classes, the following program:

class C {
  public:
    int x;
    C(int val) {
      x = val;
    }
    ~C() {}
};

int main() {
    C obj = C(1);
    return 0;
}

Gets translated to:

struct C {
  int x;
};
// Constructor
void C::ctor(struct *this, int val) {
  this->x = val;
}
// Destructor
void C::dtor() {}

struct *C __create_C(int val) {
  struct C obj;
  C::ctor(&obj, val);
  return obj;
}

int main() {
  struct C obj = __create_C(1);
  return 0;
}

For new and delete:

int main() {
  int *int_ptr = new int(5);
  delete int_ptr;

  C *obj_ptr = new C(...)
  delete obj_ptr;
  return 0;
}

Gets turned into:

struct C* __new_C(...) {
  struct C* obj = malloc(sizeof(struct C*));
  C::ctor(obj, ...);
  return obj;
}

void __delete_C(struct *C this) {
  C::dtor(this);
  free(this);
}

int main() {
  int *int_ptr = new int(5); // Encoded as a call to `alloc` from the heap model
  free(int_ptr)

  C *obj_ptr = __new_C(...)
  __delete_C(obj_ptr);
  return 0;
}