June 2010 - cffi-devel - mailman3.common-lisp.net

[cffi-devel] Foreign structures by value
by Liam Healy 26 Aug '10

26 Aug '10

I have written Foreign Structures By Value (FSBV) to allow calling foreign functions while passing or returning structures by value. It uses CFFI and libffi. It currently provides two macros for users, fsbv:defcstruct and fsbv:foreign-funcall, which are used exactly like their CFFI counterparts. It works for small test cases I've tried, but probably could use some improvement. If the keepers of CFFI are interested, I would be happy for it to be included in CFFI. In the meantime, it can be found here: http://repo.or.cz/w/fsbv.git Thank you. Liam

2 3

[cffi-devel] Foreign string arguments
by Michael Raskin 22 Aug '10

22 Aug '10

Hello. I use callback feature of CFFI. I want to use an encoding as a default and if I get an invalid string (non-UTF-8 in my case), I'd just reject it by returning an error. Unfortunately, if I declare string arguments with encoding, attempts by CFFI to decode the string raise an error which prevents me from returning protocol-compliant error to the caller. The context: I currently work on FUSE bindings for Common Lisp (or at least SBCL for now). In case of error occurring in my code, I return EIO. Of course, for invalid file names I want to return either EIO or ENOENT. Currently, request just hangs. This can be mitigated by patching CFFI. If I just wrap the conversion in ignore-errors, I lose the distinction between an invalid string and null pointer, but I get a chance to process the request (both cases are wrong in my case). Specifying a designated "wrong string object" and letting user change it seems to be the nicest way: the user gets an error on trying to use the object as a string, but user code can handle it nicely. I changed the following in string conversion code: (defmethod translate-from-foreign (ptr (type foreign-string-type)) (unwind-protect (block nil (handler-case (values (foreign-string-to-lisp ptr :encoding (fst-encoding type))) (error (x) (return t)) )) (when (fst-free-from-foreign-p type) (foreign-free ptr)))) That allowed me to handle invalid requests to the FS by returning ENOENT (just as originally intended). Would you please consider adding some similar modification in official CFFI repository? Michael Raskin

2 1

[cffi-devel] Memory fault using CFFI
by Andrew Kirkpatrick 22 Aug '10

22 Aug '10

Hi, It seems that in many cases when I call code in a library that results in a loaded foreign library function being called, I get a memory fault. Typically this error appears in my slime REPL: Help! 11 nested errors. SB-KERNEL:*MAXIMUM-ERROR-DEPTH* exceeded. 0: ; Evaluation aborted. The 11 errors appear in my *inferior-lisp* buffer, each one similar to: CORRUPTION WARNING in SBCL pid 3239(tid 3039865744): Memory fault at 100020 (pc=0x9c77963, sp=0xb52f6110) The integrity of this image is possibly compromised. Continuing with fingers crossed. Crossed fingers or not, from that point on the lisp image is unstable. It happens when I try to use Elephant to open a BDB store, or when I use CL-SQLITE directly to open a database. However I just discovered that I can successfully run the hello-world.lisp example in CLG. I'm using clbuild on 32bit x86 Ubuntu 9.10, that I used to install SBCL 1.0.35.1 and the latest (according to clbuild) CFFI. Looking closer at CFFI, it fails one test unexpectedly. I'm quite baffled and googling and asking on #lisp draws a blank. The failed test is below. Any ideas? Test DEFCFUN.BFF.2 failed Form: (SUM-127 (MAKE-POINTER 2746181372) (MAKE-POINTER 177623060) -32334.0 3158055028 (MAKE-POINTER 242315091) 4288001754991016425 -21047.0d0 287.0d0 18722 243379286 -8677366518541007140 581399424 -13872 4240394881 1353358999 226 969197676 -26207.0d0 6484 11150 1241680089902988480 106068320 61865 2253 (MAKE-POINTER 866809333) -31613 35616 11715 1393601698 8940888681199591845 (MAKE-POINTER 1524606024) 805638893 3315410736 3432596795 (MAKE-POINTER 1490355706) 696175657106383698 -25438.0 1294381547 26724 (MAKE-POINTER 3196569545) 2506913373410783697 -4405955718732597856 4075932032 3224670123 2183829215657835866 1318320964 -22 -3786.0d0 -2017024146 1579225515 -626617701 -1456 (MAKE-POINTER 3561444187) 395687791 1968033632506257320 -1847773261 48853 142937735275669133 -17974.0 (MAKE-POINTER 2791749948) -14140.0 2707 3691328585 3306.0 1132012981 303633191773289330 (MAKE-POINTER 981183954) 9114.0d0 8664374572369470 -19013.0d0 -10288.0d0 -3679345119891954339 (MAKE-POINTER 3538786709) 23761 -154264605 (MAKE-POINTER 2694396308) 7023 997.0d0 1009561368 241 (MAKE-POINTER 2612292671) 48 1431872408 -32675.0d0 (MAKE-POINTER 1587599336) 958916472 -9857.0d0 111 -14370.0d0 -7308 -967514912 488790941 2146978095 -24111.0d0 13711 86681861 717987770 111 1013402998690933877 17234.0d0 -8772.0 3959216275 -8711 (MAKE-POINTER 3142780851) 9480.0 -3820453146461186120 1616574376 -3336232268263990050 -1906114671562979758 -27925.0d0 9695970875869913114 27033.0d0 1096518219 -12 104 3392025403 -27911 60 89 509297051 -533066551 29158.0 110 54 -9802.0d0 593950442165910888 -79) Expected value: 7758614658402721936 Actual value: 7758614624042983568. Thanks! -- Andrew Kirkpatrick "The first rule of Perl Club... has subscript 0. Unless you changed $[. But don't!" -- blazar on perlmonks.org

2 1

[cffi-devel] help with load-foreign-library
by N J 01 Jul '10

01 Jul '10

Hi, I have a question about how to find a function in the opencv library. I tried this: (require :cffi) ;; load shared libs (cffi:load-foreign-library "libcv.so") (cffi:load-foreign-library "libhighgui.so") ;; define the function call CvCapture* capture = cvCaptureFromCAM( -1 ); (cffi:defctype cvcapture :pointer) (cffi:defcfun "cvCaptureFromCAM" cvcapture (type :int)) But I get: STYLE-WARNING: Undefined alien: "cvCaptureFromCAM" Which means that "cffi" cannot find the name in the shared object file. My shared object file looks like this: nm /usr/lib64/libhighgui.so | grep -i cvcapturefromcam 000000000023d180 b _ZZL21icvCaptureFromCAM_V4LiE9autoindex nm /usr/lib64/libhighgui.so | grep -i cvcapturecam 0000000000021760 t _ZL15icvCloseCAM_V4LP16CvCaptureCAM_V4L 0000000000021fa0 t _ZL15icvSetVideoSizeP16CvCaptureCAM_V4Lii 00000000000225f0 t _ZL19icvGrabFrameCAM_V4LP16CvCaptureCAM_V4L 00000000000216a0 t _ZL33v4l2_scan_controls_enumerate_menuP16CvCaptureCAM_V4L 0000000000021940 T _ZN20CvCaptureCAM_V4L_CPP11getPropertyEi 00000000000221c0 T _ZN20CvCaptureCAM_V4L_CPP11setPropertyEid 0000000000021d60 T _ZN20CvCaptureCAM_V4L_CPP13retrieveFrameEi 0000000000022a10 T _ZN20CvCaptureCAM_V4L_CPP4openEi 0000000000021880 T _ZN20CvCaptureCAM_V4L_CPP5closeEv 00000000000229f0 T _ZN20CvCaptureCAM_V4L_CPP9grabFrameEv 00000000000218b0 W _ZN20CvCaptureCAM_V4L_CPPD0Ev 0000000000021900 W _ZN20CvCaptureCAM_V4L_CPPD1Ev 000000000023af40 V _ZTI20CvCaptureCAM_V4L_CPP 0000000000033c20 V _ZTS20CvCaptureCAM_V4L_CPP 000000000023aee0 V _ZTV20CvCaptureCAM_V4L_CPP 000000000023d174 b _ZZL21icvSetPropertyCAM_V4LP16CvCaptureCAM_V4LidE5width 000000000023d170 b _ZZL21icvSetPropertyCAM_V4LP16CvCaptureCAM_V4LidE6height Questions: 1) Am I doing it all wrong or can one do like this? 2) Is there a smart way to use the .so file to get the correct name of functions?

4 5

[cffi-devel] passing value of different type than :int to foreign function
by N J 30 Jun '10

30 Jun '10

Hi, I have a question about passing values to foreign functions that are not :int. If I define a foreign function as (cffi:defcfun "foo" :void (val :double)) I am not able to call it with (foo 45.0) Because 45.0 is not of type :double. I have tried different ways (convert-to-foreign and so on) but I cannot solve it. Any help is greatly appriciated. // Nik

3 3

[cffi-devel] cffi-grovel's output
by Tobias C Rittweiler 28 Jun '10

28 Jun '10

CFFI grovel outputs to *DEBUG-IO* (in INVOKE), I think it should better output to ASDF::*VERBOSE-OUT*. Reason is that this way, CFFI grovel will automatically play nice with ASDF's :VERBOSE keyword parameter. -T.

1 0

[cffi-devel] CFFI and FORTRAN CHARACTER*(*)
by Tamas K Papp 07 Jun '10

07 Jun '10

Hi, I am trying to call the FORTRAN routine ILAENV in LAPACK [1] from CL, using CFFI. It has CHARACTER*(*) arguments, and I am not sure how to handle these. I found a lot of conflicting information on the web, including examples which used C-style zero-terminated strings [2], and others which mention string length as an extra argument to the function. Any kind of guidance on how to do this would be appreciated. Thanks, Tamas [1] http://www.netlib.org/lapack/util/ilaenv.f [2] http://www.ualberta.ca/AICT/RESEARCH/LinuxClusters/doc/acml350/ ILAENV_002dILAENVSET.html

4 5

[cffi-devel] CFFI and wait (2)
by Lorenzo Villani 01 Jun '10

01 Jun '10

Hi, I'm trying to use CFFI in order to wrap execve (2). The wrapper also uses fork (2) and wait (2). While I have absolutely no problems with execve or fork I'm stumbling on a problem with wait. Wait takes a pointer to an int to store child process' status. The problem is: after the call to wait the value stored in the pointer is the same as before the call. I am using CFFI 0.10.5 and GNU CLISP 2.47 on Fedora 13. The code follows: (defcfun ("fork" c-fork) :int) (defcfun ("execve" c-execve) :int (filename :string) (args :pointer) (env :pointer)) (defcfun ("wait" c-wait) :int (status :pointer)) (defun execute-program (path argv env) (let ((child-pid (c-fork))) (if (= child-pid -1) (error "Unable to create child process") (if (= child-pid 0) ;; Child (progn ;; Remember: (nth 0 argv) must be the full path to the executable. (let ((c-argv (foreign-alloc :string :initial-contents (append (list path) argv) :null-terminated-p t)) (c-env (foreign-alloc :string :initial-contents env :null-terminated-p t))) (c-execve path c-argv c-env) (foreign-free c-argv) (foreign-free c-env))) ;; Parent code (progn (let ((wait-status (foreign-alloc :int))) (c-wait wait-status) ;; This test condition is a reimplementation of __WIFEXITED macro defined at ;; /usr/include/bits/waitstatus.h (if (= 0 (logand (mem-ref wait-status :int) #x7f)) ;; This test condition is a reimplementation of __WEXITSTATUS macro defined at ;; /usr/include/bits/waitstatus.h (when (/= 0 (ash (logand (mem-ref wait-status :int) #xff00) -8)) (error "Child returned an error")) (error "Failed to execute child process")) (foreign-free wait-status))))))) -- Lorenzo Villani <lvillani(a)binaryhelix.net>

3 3

[cffi-devel] utf-16
by Helmut Eller 01 Jun '10

01 Jun '10

Is this assertion (assert (equal (cffi:with-foreign-string (data "foobar" :encoding :utf-16) (cffi:foreign-string-to-lisp data :count 6 :encoding :utf-16)) "foobar")) expected to fail? Helmut

2 4

[cffi-devel] ccl32
by Helmut Eller 01 Jun '10

01 Jun '10

I think there is a bug in CFFI with CCL's 32-bit version: (cffi:defcunion foo-union (int16 :int16 ) (uint64 :uint64 ) ) (cffi:defcstruct bar-struct (tag :uint8) (val foo-union)) (defun foo () (cffi:with-foreign-string (data "0123456789" :encoding :latin-1) (- (cffi:pointer-address (cffi:foreign-slot-value data 'bar-struct 'val)) (cffi:pointer-address data)))) FOO returns 4 in SBCL and Lispworks but with CCL it's 8. Helmut

1 0