[CERT-C mapping] Correctness of mapping of FIO34 / FIO37

[darkwisebear]

FIO34 and FIO37 talk about undefined behavior under certain circumstances, when using STREAM based C APIs (fopen, fread, ...). These rules are marked as "not applicable" to Rust. However, one can call these functions in Rust, so that calling them in the wrong way will lead to UB also in Rust.

Open points:

• Since these functions can be called in Rust, would these rules (and maybe others) need to be re-categorized?
• If so, would we need a new rule to cover this case more specifically, or does the general "do not do bogus things in unsafe" cover this?

[riking]

I think I'd be in favor of a "don't call libc buffered IO functions from Rust" rule, maybe with "Do not interleaves IO between C buffered functions and Rust read/write calls"

If you need to interleave, write a wrapper layer that translates the semantics correctly I guess?