How signed or unsigned integers are used to keep track of heap-allocated objects in C?

Question

Many OpenGL functions; for instance, "GLuint glCreateShader()" keep track of created objects (in this case, a "Shader" object) without returning a pointer. Because the maximum size of an unsigned can be 4 bytes, so it wouldn't make sense to cast it to a pointer type (since a pointer has a size of 8 bytes) to use it as a reference to the created "Shader" object. I hope it is clear enough. Hope someone with proper knowledge would give an answer or give a reference of some sort. Thanks

Answer 1

Did you understand the question? Sonic

Answer 2

Lucas perhaps not 100% as I don't use OpenGL. Would you mind elaborating?

Answer 3

Sonic It's been explained already. It's not about opengl, but how opengl implements such functions Anyway, it's better not to answer if someone may lack knowledge about something. Thanks

Answer 4

Perhaps you can post the question in a Khronos forum?

Answer 5

Pointers are 8 bytes long because they store addresses. What is contained at or starts at those addresses in the heap can be any length.

Answer 6

Martin Taylor i know it's not a pointer. I wanted to know, how could i write such kind of function. Any idea how one can implement such function i.e. return a handle instead of a pointer and do all the things (access, update. ..)?

Answer 7

Martin Taylor well, I'm not writing any game. It's a bit of pity to get judged about knowledge/experience based on some silly XP convention.

bringing "OpenGL" to ask about a C related question was to give an example. The underlying question was "how a handle can be used to manipulate an object in heap-allocated memory?". Even WIN32 API also returns handles, but that handle is a simple "void*" with a size of 8 bytes, so it could technically be cast to the desired pointer.

I'm not solving any homework, and "not showing any attempt" is not appropriate for this particular question I think. I actually searched a bit online before asking this question but failed to get any valid implementation of OpenGL. Could you point me one?

I like the idea of using a "map", but you mentioned there are other ways. Could you just mention those? I just need the names/terms then I should be able to implement them myself. Thanks