[Openmcl-devel] Simple FFI Newb questions...

Michael Kohout mwkohout at gmail.com
Fri Aug 7 16:05:46 PDT 2009

Thanks fellas; that seems to have gotten me somewhere.
I was able to open the shared lib and the interface file to initialize the
CL-USER> (open-shared-library "/usr/lib/libpython2.5.so")
#<SHLIB libpython2.5.so.1.0 #x30004138361D>
CL-USER> (use-interface-dir :python25)
#<INTERFACE-DIR :PYTHON25 #P"python25/" #x3000414D738D>
CL-USER> (#_Py_Initialize)

Next, I try to call a function that cakes a simple char array but am getting
an error:
 (with-cstrs ((simple "print 'hello'")) (#_PyRun_SimpleString simple))
errors with:
Foreign function not found: X86-LINUX64::|PyRun_SimpleString|

I can find the symbol (or whatever) via  (external "PyRun_SimpleString"), so
what am I doing wrong?

thanks again,

On Fri, Aug 7, 2009 at 1:33 PM, Gary Byers <gb at clozure.com> wrote:

> The #_ reader macro expects to read a case-sensitive foreign function name,
> as in:
> (#_Py_Initialize [whatever args it takes if any])
> At some point, #_ winds up interning a mixed-case symbol in the OS
> package and defining that symbol as a macro that expands into some
> sort of foreign-function call.  Those symbols might show up in error
> messages or backtraces, but you don't generally deal with them directly.
> Foreign types (and field accessors) are represented as keywords with
> upper-case substrings surrounded by angle brackets.  The canonical
> rectangle type used in Cocoa is called "NSRect" in ObjC, which is
> represented as :<NSR>ect in CCL's FFI.  That can get pretty difficult
> to type (and to read); the #> reader macro reads a case-sensitive string
> and returns a keyword with angle brackets in the right places:
> ? #>NSRect
> :<NSR>ect
> which is at least slightly better than having to type the angle brackets
> yourself.
> If you mix the two (#_ and #>), you get the behavior that you got: the
> FFI can't find a foreign function named by a keyword that contains angle
> brackets in its name.  (I suppose that we -could- try to interpret that
> as a foreign function name and install a macro on the keyword, but we
> don't.)
> On Fri, 7 Aug 2009, Michael Kohout wrote:
>  Hi all-
>> Inspired by a previous post, I'm trying to import python2.5 using ccl's
>> ffi,
>> but I'm having troubles.
>> I've built and run ffigen, written my populate.sh script, called it from
>> within ccl with (ccl:create-interfaces :python25), and referenced those
>> interfaces with  (use-interface-dir :python25).
>> After which I try to call a function defined by python's c api:  (#_
>> #>Py_Initialize)
>> However, when I try to call a function defined in python's c lib, I get an
>> error:
>> Foreign function not found: :<P>Y_<I>NITIALIZE
>> Any suggestions?  Am I missing any steps?
>> thanks
>> Mike Kohout
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