Question

I’m parsing some structures for a game. I know most things about the structures, but there are various things I don’t know, nor do I really care about them. But I need them in my parsing so things line up. For example:

template <unsigned int Size>
class unknown
{
    BYTE data[Size];
};

struct s_object
{
    int stuff;
    unknown<100> unk1;
    int otherstuff;
    unknown<200> unk2;
};

This is a contrived example but it shows what I’m trying to do. I don’t like having to name members unk1 and then unk2. Ideally I’d like to do this

 struct s_object
    {
        int stuff;
        unknown<100>;
        int otherstuff;
        unknown<200>;
    };

But of course that doesn’t work. Is there a way for the compiler to either generate a random name, use no name, or maybe just treat it as padding?

Answer 1

You can use the __COUNTER__ macro (but will need some preprocessor trickery). It is implemented by GCC, Visual C++ and probably others.

You can then define a macro named, for example _ that expands to something like _unused_15, _unused_16 and so on upon use. With it your code will become:

struct s_object
{
    int stuff;
    unknown<100> _;
    int otherstuff;
    unknown<200> _;
};

The trickery being, i.e.

#define CAT(a,b)           a##b
#define CAT_DELAYED(a,b)   CAT(a,b)
#define _                  CAT_DELAYED(_unused_,__COUNTER__)