[cffi-devel] help with load-foreign-library

[Stelian Ionescu]

On Wed, 2010-06-30 at 18:37 +0200, N J wrote:
> 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?

That library seems to be C++ or a C library compiled with the C++
compiler and it doesn't export functions with C linkage, so you need to
make one yourself

-- 
Stelian Ionescu a.k.a. fe[nl]ix
Quidquid latine dictum sit, altum videtur.
http://common-lisp.net/project/iolib
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