ctest: support variadics in function pointers

[tgross35]

ctest should be able to generate tests for functions that make use of varidics. See JohnTitor/ctest2#58 for context.

Edit: The above works since #5385, but we should ideallly cover variadics in function pointer aliases and struct/union fields as well.

[tgross35]

We have the c_variadic feature stabilizing in the next version rust-lang/rust#155697, this should make things more workable.

[tgross35]

@mbyx I think that with c_variadic being stabilized this may "just work" now (assuming we test on nightly of course). Would you mind submitting a PR testing it?

[tgross35]

Actually some of the syntax bits may have to be updated to emit ...

[mbyx]

Actually, since the way foreign functions are tested changed in the new ctest, we don't construct the type at all. The variadic part remains in the C source, but is never used in the .C test (because we cast to a void pointer), nor in the Rust test (since we just call the foreign_fn_ptr function that takes no arguments and just returns a function pointer with no type information).

It would really only affect structs that have a function pointer I think.

[tgross35]

That PR pretty much fixed everything but it would be good to handle function pointers as well, so I'll reopen for that

[mbyx]

I believe the PR also handles function pointers as well. I just checked locally by adding a variadic function pointer to a struct field in the tests, and the tests seem to pass:

struct Person
{
    const char *name;
    uint8_t age;
    void (*job)(uint8_t, const char *, ...);
    enum Color favorite_color;
};

Which generates this test (among others):

typedef void (**ctest_field_ty__Person__job)(uint8_t, const char *, ...);
CTEST_EXTERN ctest_field_ty__Person__job
ctest_field_ptr__Person__job(struct Person *b) {
    
    ctest_field_ty__Person__job ptr;
    ptr = &b->job;
    (void)ptr; 

    return &b->job;
}

If this is enough, then when I eventually make a PR regarding testing improvements, I'll add in this specific test as well.

[tgross35]

Oh awesome! Yeah that's all, a test would be great