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.
Could you elaborate where there's a consing issue, if errno is returned as the last, or first, value? On Wed, Aug 14, 2013 at 12:15 AM, Luís Oliveira <luis...@gmail.com> wrote: > Felix Filozov <ffilo...@gmail.com> writes: > > > If I understood Duane Rettig's response correctly, when a thread binds > > a special variable using a let, that binding is only visible for that > > particular thread. Is this how other Lisps behave? > > All CLs I'm aware of behave like that, yes. > > > > With that in mind, in order to make with-errno work, the foreign > > function call expression would have to be identified and bound with a > > let. > > Why is that? I was thinking that the interface could work as follows: > > 1. WITH-ERRNO establishes a dynamic binding (cffi-sys:*errno* for > instance) > 2. FOREIGN-FUNCALL does something like > (when (boundp '*errno*) (setf *errno* <errno>)) > 3. GET-ERRNO simply returns the value of *errno* > > > > You mentioned that a foreign function call could return errno as the > > first value, how about returning it as the last? > > That would be much simpler wouldn't it? I wonder if we can avoid > consing, at least for the single return value case... If all else fails, > simply documenting that grabbing errno entails discarding all but the > first return value might be a solution. > > > > Another alternative is to optimize the way synchronization is done, so > > that we could improve the thread-local code I wrote before. > > I don't have any good ideas on that front. > > Luís > > >
