Use a `final_action` object to express cleanup if no suitable resource handle is available

Reason

finally from the GSL is less verbose and harder to get wrong than try/catch.

Example

void f(int n)
{
    void* p = malloc(n);
    auto _ = gsl::finally([p] { free(p); });
    // ...
}

Note

finally is not as messy as try/catch, but it is still ad-hoc. Prefer proper resource management objects. Consider finally a last resort.

Note

Use of finally is a systematic and reasonably clean alternative to the old goto exit; technique for dealing with cleanup where resource management is not systematic.

Enforcement

Heuristic: Detect goto exit;