cffi-devel December 2013

cffi-devel@common-lisp.net

3 participants
3 discussions

Returning errno as a second value
by Felix Filozov 28 Jan '14

28 Jan '14

Hi all, In Allegro CL, the only safe way to get errno after a foreign function call is to configure the foreign function definition to return it as a second value. CFFI doesn't deal with errno. There has been some previous discussion ( http://lists.common-lisp.net/pipermail/cffi-devel/2009-January/003017.html) to return errno safely, but doesn't seem like it went anywhere. So any library that tries to get errno is potentially broken in Allegro CL. I'm seeing this in practice with lisp-zmq, for example. I'd like to introduce a new option to defcfun and foreign-funcall called :errno. It would look like this: (foreign-funcall ("strlen" :errno t) :string "foo" :int), or (defcfun (strlen "strlen" :errno t) :int (s :string)). Calling (strlen) would return two values, the return value of the foreign call, and errno. In some Lisps, the only way to get errno is to make an additional foreign call. Then perhaps that call could be made by CFFI and returns as the second value. I've created a pull request (https://github.com/cffi/cffi/pull/28) with a very rudimentary implementation for Allegro CL. Since CFFI delegates the handling of errno to the implementation, perhaps we could preserve the status quo and not get bugged down in grandiose plans of portability. Thoughts and suggestions are welcome. Thanks, Felix

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[cffi-devel] Recommended way to specify libraries
by Elliott Slaughter 04 Jan '14

04 Jan '14

>From [1] I see the following code example (*define-foreign-library* libcurl (:unix (:or "libcurl.so.3" "libcurl.so")) (t (:default "libcurl"))) with the comment "the define-foreign-library clause (t (:default "libcurl"))[...] will adapt to various operating systems". I'm wondering exactly how smart is this automatic handling? On Windows, for example, the conventions are not always followed so closely, and as a result I keep adding more special cases to my define-foreign-library clauses when users complain they can't load the libraries. For example, libpng might be png.dll or libpng.dll or libpng12.dll or libpng12-0.dll or libpng15-15.dll. Will I be required to maintain a list of all possible names for the rest of eternity or is there some better way to manage this situation? Thanks. [1]: http://common-lisp.net/project/cffi/manual/cffi-manual.html#Tutorial_002dLo… -- Elliott Slaughter "Don't worry about what anybody else is going to do. The best way to predict the future is to invent it." - Alan Kay

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[cffi-devel] How to define a pointer to a 2d array
by Joeish W 08 Dec '13

08 Dec '13

I have a function that accepts a void* as a parameter Im trying to convert this to use as the void* float trainingData[4][2] = { {501, 10}, {255, 10}, {501, 255}, {10, 501} }; this is how i do a void* 1d array float labels[4] = {1.0, -1.0, -1.0, -1.0}; (labels (foreign-alloc :float :initial-contents '(1.0 -1.0 -1.0 -1.0))) so how do i do the 2d array

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cffi-devel December 2013