What does a C++ class look like in assembly

Question

I am planning to do some reverse engineering on an application that was written in a object oriented way. And now I'm kind of curious what a C++ class would look like in assembly. I already found out the basics about functions and their calling conventions. But classes are probably way more complex, right?

So let's say we have this class:

class Rectangle {
    int width, height;
  public:
    void set_values (int,int);
    int area() {return width*height;}
};

void Rectangle::set_values (int x, int y) {
  width = x;
  height = y;
}

and this object:

Rectangle rect;
rect.set_values (3,4);

What would/could it look like in assembly?

even for simple C code, the assembly output depends on compiler and compiler options. To see how the output is in various compilers, use GCC Godbolt compiler explorer — phuclv, Oct 08 '15 at 16:55

score 8 · Answer 1 · edited Apr 13 '17 at 12:49

8

As discussed in https://reverseengineering.stackexchange.com/a/5957/1562, it's compiler-dependent (different compilers will generate different machine code and data structures).

However, you may want to refer to Reversing C++, as it does a pretty good job showing how most compilers compile C++ classes.

edited Apr 13 '17 at 12:49

Community

1

answered Oct 08 '15 at 12:37

Jason Geffner

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The reversing C++ paper is invaluable. – Nov 03 '17 at 13:20
In the microsoft x64 convention where RCX, RDX, R8, R9 are used are arguments, is RCX still used by c++ for the this pointer ? – Herz3h Jul 13 '21 at 18:47

What does a C++ class look like in assembly

1 Answers1