"Luís Oliveira" <luis...@gmail.com> writes:
> On Fri, Jan 9, 2009 at 1:06 AM, John Fremlin <j...@msi.co.jp> wrote:
>> However, there is no guarantee that between calling your function and
>> getting the errno, the Lisp environment will not call a C function that
>> resets errno.
>
> I guess this is more of a problem in Lisps with userspace threads. Are
> there other situations? (Signal handlers shouldn't mess with errno...
> Maybe GC hooks?) Any idea how Allegro implements this?
I'm not sure. I asked them and Duane said that wrapping with
without-interrupts might be okay
(defmacro with-errno (&body body)
`( ,(progn
'progn
#+allegro 'excl:without-interrupts)
(locally ,@body) (get-errno)))
I asked about whether this might not work in the event of GC and got no
answer.
>> In SBCL there is a native get-errno function to get the errno.
>>
>> Is there any plan to add a semi-portable wrapper to this functionality
>> for CFFI?
>
> Adding a CFFI-SYS:GET-ERRNO function sounds like a good idea. I don't
> understand the other bit well enough yet to have an opinion.
It'd be great to be able to use the def-foreign-call Allegro
functionality.
ClozureCL has something slightly similar called int-errno-call
(defmacro int-errno-call (form)
(let* ((value (gensym)))
`(let* ((,value ,form))
(if (< ,value 0)
(%get-errno)
,value))))
>> If not, would you accept a patch for it? I guess the obvious way is to
>> modify (cffi:defcfun ...) to take a :after-collect-value argument, so
>> that it could work not only for errno
>
> Indeed, it'd be useful for GetLastError() as well, etc.
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