Re: [PATCH 0/6] RFC: adding support to GCC for detecting trust boundaries

[Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>]

On Sat, Nov 13, 2021 at 9:37 PM David Malcolm <dmalcolm@redhat.com> wrote:
>
>   #define __user __attribute__((untrusted))
>
> where my patched GCC treats
>   T *
> vs
>   T __attribute__((untrusted)) *
> as being different types and thus the C frontend can complain (even without
> -fanalyzer) about e.g.:

This one sounds similar to the `Untrusted<T>` wrapper I suggested for
the Rust side -- we would have a method to "extract and trust" the
value (instead of a cast).

> Patch 2 in the kit adds:
>   __attribute__((returns_zero_on_success))
> and
>   __attribute__((returns_nonzero_on_success))
> as hints to the analyzer that it's worth bifurcating the analysis of
> such functions (to explore failure vs success, and thus to better
> explore error-handling paths).  It's also a hint to the human reader of
> the source code.

These two sound quite nice to have for most C projects. Would it be
useful to generalize to different values than 0/non-0? e.g.
`returns_on_success(0)` and `returns_on_failure(0)`.

Cheers,
Miguel