pointer to array not compatible to a pointer to 'const' array?

Question

In a C module (aka, compilation unit), I want to have some private data, but expose it read-only to the outside world. I achieve that by having a field in a s

Answer 1

I am not entirely sure if this could be considered a good idea, but something that I do sometimes when I'm feeling lazy is to define a "const cast" macro like:

#define CC(_VAR) ((const typeof(_VAR))(_VAR))

This of course assumes that you have a compiler that supports the typeof extension. Using this (dubious) construction you could then write

const shape *fooshapes(const foo *f)
{
    return CC(f->shapes);
}

Otherwise, C doesn't generally cast to const implicitly. You do have to explicitly cast pointers to const pointers.