bug#18592: FFI should have portable access to ‘errno’

[Chaos Eternal <chaoseternal@shlug.org>]

On Tue, Jan 5, 2016 at 3:14 AM, Nala Ginrut <nalaginrut@gmail.com> wrote:
> Hi Mark!
> Thanks for all the advices.
>
> Here's the new patch according to your advices.
> Include:
> 1. Added new procedure pointer->procedure-with-errno with
> #:return-errno?
>
> Question: Should we make #:return-errno? true in default? This would
> make the name *-with-errno more reasonable. At present, it's false in
> default.
>

I suggest that if we have this new procedure, we don't need keyword
option "#:return-errno?" since the procedure name itself implies it.
Also if old behavior is needed, the old procedure pointer->procedure
still can be employed.

> 2. Used scm_cons2
>
> 3. Store errno to a local var after ffi_call immediately.
>
> 4. Set errno=0 only when #:return-errno? is true.
>
> 5. Merged all modifications into one patch.
>
> Comments please.
>
> Best regards.
>