July 2013 - cffi-devel - mailman3.common-lisp.net

Allowing GC in Allegro CL SMP during foreign function calls
by Felix Filozov 21 Aug '13

21 Aug '13

Hi all, When defining a foreign function using def-foreign-call, there's an option one could set called :allow-gc. Setting it to :always, allows the garbage collector to run while the foreign function is executing. At the moment CFFI uses the default value for :allow-gc, which is :never. This prevents GC from running when a foreign function is executing. Moreover, once GC blocks, other processes can't make progress. In my case, I need GC to run during foreign function execution. What do you think about extending the defcfun and foreign-call interfaces to allow for native options to be passed? name-and-options could be extended to accept a new argument, :native-args, for example. Then you'd be able to use defcfun as follows: (defcfun ("strlen" :native-args (:allow-gc :always)) :int (str :string)) Another option is to create a global variable that holds native arguments, and def-foreign-call would read this directly. Thanks, Felix

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Problems with nested structs and the newer cffi
by Willem Rein Oudshoorn 18 Aug '13

18 Aug '13

I am encountering some problems with trying to upgrade my old cffi code to the new version from quicklisp. If I use the old code, I get lots of warnings about my structs, that I should use either (:struct ...) or (:pointer (:struct ...)) However whateer I try, I do not seem to get it to work, and I am starting to think there is some issue between me and the new cffi. The main issue is a nested struct definition like this: ``` (defcstruct timeval (time %time) (offset :int)) (defcstruct (git-signature) (name :string) (email :string) (time (:struct timeval))) ``` With type definitions ``` (define-foreign-type time-type () nil (:actual-type :int64) (:simple-parser %time)) (define-foreign-type git-signature-type () nil (:actual-type :pointer) (:simple-parser %git-signature)) ``` I encounter problems when I am trying to update the `translate-to-foreign` for the `git-signature-type`. The implementation boils down to: ``` (defmethod translate-to-foreign ((value list) (type git-signature-type)) (let ((signature (foreign-alloc '(:struct git-signature)))) (with-foreign-slots ((name email time) signature (:struct git-signature)) (setf name (getf value :name (getenv "USER"))) (setf email (getf value :email (default-email))) (with-foreign-slots ((time offset) time (:struct timeval)) (let ((time-to-set (getf value :time (local-time:now)))) (setf time time-to-set) (setf offset (/ (local-time:timestamp-subtimezone time-to-set local-time:*default-timezone*) 60))))) signature) ``` The problem is in the inner `with-foreign-slots ((time offset)...`. The error I get is: ; Evaluation aborted on #<TYPE-ERROR expected-type: SYSTEM-AREA-POINTER datum: (CL-GIT::OFFSET 0 TIME @1970-01-01T01:00:03.000000+01:00)>. The reason is, as far as I can tell, that in the code: (with-foreign-slots ((time offset) time (:struct timeval)) ... the value of `time` is already a plist (due to the outer with-foreign-slots), and the inner with-foreign-slots expects a pointer. So what is the best way of fixing this? I can fix this by replacing the inner `with-foreign-slots` by ``` (with-foreign-slots ((time offset) (foreign-slot-pointer signature '(:struct git-signature) 'time) (:struct timeval)) ``` which seems a bit long. An additional question is, when to use (:struct ...) and when to use (:pointer (:struct ..))) I did expect that I needed to use (:pointer (:struct ..)) in the toplevel `with-foreign-slots`, because the argument is actually a pointer to the struct. But that did not work. As you can tell, I am a bit confused. Hope that someone can give some hints to clear my head. Kind regards, Wim Oudshoorn.

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cffi-grovel::*auto-export*
by FAU 07 Jul '13

07 Jul '13

Hello, I was looking for a way to auto export and found that switch. Setting it to T does the job. Well I noticed it is not exported so why not exporting it? Thanks, Frank

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bitfield improvement pull request
by Nicolas Martyanoff 04 Jul '13

04 Jul '13

Hi, I just created a pull request for a patch I wrote: https://github.com/cffi/cffi/pull/26 Do not hesitate to contact me if any modification is needed. Regards, -- Nicolas Martyanoff http://wandrian.net khaelin(a)gmail.com

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wrong link on website
by Nicolas Martyanoff 02 Jul '13

02 Jul '13

Hi, For your information, the link to the mailing list info page of CFFI is not valid anymore on http://common-lisp.net/project/cffi/ (404). Regards, -- Nicolas Martyanoff http://wandrian.net khaelin(a)gmail.com

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Example with sprintf & %f from cffi manual crashes clisp on cygwin
by Mirko Vukovic 01 Jul '13

01 Jul '13

Hello, The following example from section 10 of the cffi documentation is causing a segmentation fault on clisp on cygwin: (defcfun "sprintf" :int (str :pointer) (control :string) &rest) CFFI> (with-foreign-pointer-as-string (s 100) (sprintf s "%c %d %.2f %s" :char 90 :short 42 :float 3.1415 :string "super-locrian")) => "A 42 3.14 super-locrian" I replaced :float pi with :float 3.1415, as ``pi'' is long-float - I wanted to remove this as a possible cause. At first I thought it was the %s for the string, but it may actually be the %.2f. - By itself %f, it does not correctly process floats, emitting ``f''. - If followed by other codes, it swallows them - If followed by a string, causes a segmentation fault CL-USER> (cffi:with-foreign-pointer-as-string (s 100) (sprintf s "%s" :string "super-locrian")) "super-locrian" CL-USER> (cffi:with-foreign-pointer-as-string (s 200) (sprintf s "%.2f" :float 3.1415)) "f" CL-USER> (cffi:with-foreign-pointer-as-string (s 200) (sprintf s "%.2f %c" :float 3.1415 :char 65)) "f " CL-USER> (cffi:with-foreign-pointer-as-string (s 200) (sprintf s "%.2f %s %c" :float 3.1415 :string "five" :char 65)) Segmentation fault I'll try this on Linux/SBCL when I get back to work on Monday. Mirko

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