Hi Luís, I am hoping to resurrect this thread. Did you by any chance take a look at the pull request <https://github.com/cffi/cffi/pull/31> I made a few months ago relating to this feature?
Thanks, Felix On Wed, Aug 14, 2013 at 6:26 PM, Felix Filozov <ffilo...@gmail.com> wrote: > I have a with-errno > <https://github.com/ffilozov/cffi/tree/with-errno>implementation. > > > On Wed, Aug 14, 2013 at 5:23 PM, Felix Filozov <ffilo...@gmail.com> wrote: > >> Ah, I understand why it has to be dynamic now. I'll start working on >> with-errno then. >> >> The consing problem is clearer now, but I wonder how much overhead it >> adds compared to the cost of making a foreign call. According to the >> Allegro CL documentation, a foreign call which returns errno is less >> efficient. For other Lisps, an additional foreign call would have to be >> made to get errno. Maybe consing is negligible? >> >> >> On Wed, Aug 14, 2013 at 3:04 PM, Luís Oliveira <luis...@gmail.com> wrote: >> >> Felix Filozov <ffilo...@gmail.com> writes: >>> >>> > Maybe we can even do this using lexical binding, since GET-ERRNO could >>> > be a macro that expands to a lexical variable introduced by >>> > WITH-ERRNO. >>> >>> The issue there is that foreign-funcall will be setting errno. >>> >>> >>> > Could you elaborate where there's a consing issue, if errno is >>> > returned as the last, or first, value? >>> >>> So, the pseudo-code for the implementation in foreign-funcall would be >>> something like: >>> >>> (multiple-value-bind (return-value errno) >>> (%foreign-funcal ...) >>> (let ((translated-return-values (multiple-value-list >>> (translate-from-foreign ...)))) >>> (values-list (cons errno translated-return-values)) >>> ;; or (values-list (nconc translated-return-values (list errno))) >>> )) >>> >>> Right now I'm inclined to discard all but the first translated return >>> value. (This is your initial solution, isn't it?) >>> >>> Luís >>> >>> >>> >> >> On Wed, Aug 14, 2013 at 3:04 PM, Luís Oliveira <luis...@gmail.com> wrote: >> >>> Felix Filozov <ffilo...@gmail.com> writes: >>> >>> > Maybe we can even do this using lexical binding, since GET-ERRNO could >>> > be a macro that expands to a lexical variable introduced by >>> > WITH-ERRNO. >>> >>> The issue there is that foreign-funcall will be setting errno. >>> >>> >>> > Could you elaborate where there's a consing issue, if errno is >>> > returned as the last, or first, value? >>> >>> So, the pseudo-code for the implementation in foreign-funcall would be >>> something like: >>> >>> (multiple-value-bind (return-value errno) >>> (%foreign-funcal ...) >>> (let ((translated-return-values (multiple-value-list >>> (translate-from-foreign ...)))) >>> (values-list (cons errno translated-return-values)) >>> ;; or (values-list (nconc translated-return-values (list errno))) >>> )) >>> >>> Right now I'm inclined to discard all but the first translated return >>> value. (This is your initial solution, isn't it?) >>> >>> Luís >>> >>> >>> >> >
