Some issues with C callouts

> Hi everybody!
>
> I am going to write the XCB binding for GNU Smalltalk and now I'm
> playng with C call-outs.
>
> I've got an issue in the case when C function returns a structure
> itself (not a pointer).
>
> There are two files in attachments:
>  * rootwin.c - the C code that aquires current screen and prints the
> root window's ID
>  * xcbroot.st - the Smalltalk port of rootwin.c
>
> `--> ./rootwin
> root window 163
>
> `--> gst -f xcbroot.st
> xcbroot.st:56: Aborted
> (ip 10)CUInt(CScalar)>>#value
> (ip 6)UndefinedObject>>#executeStatements
> (ip 0)<bottom>
> zsh: abort      gst -f xcbroot.st
>
> I assume that I missunderstood something about pointer-to-structure
> conversions, however I wrote this code according to GST manual (C data
> types, etc). I think I did something wrong.
>
> Could anybody please help me with this problem?
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> Thank you for advice, Gwenael, however unfortunately it did not solved
> the problem :(
>
> 2009/9/28, Gwenael Casaccio <[hidden email]>:
> > Hi,
> >
> > The bug is here :
> >
> >     (#data (#ptr #XcbScreen))
> >
> > Change this line with :
> >
> >     (#data #{XcbScreen})
>
> Regards,
> Dmitry

>> In this case, you should create a wrapper to xcb_setup_roots_iterator
>> that accepts a pointer to the structure and copies the return value there.
>>
>
> Thank you, Paolo!
>
> I've made the following:
>
> void
> gst_xcb_setup_roots_iterator (const xcb_setup_t *setup,
>  xcb_screen_iterator_t *iter)
> { if (setup&&  iter)
> *iter = xcb_setup_roots_iterator (setup);
> }
>
> in my shared library and
>
> Xcb class>>  setupRootsIterator: aSetup ptr: iterPtr [
>      <cCall: 'gst_xcb_setup_roots_iterator' returning: #void args:
> #(#cObject #{XcbScreenIterator})>
> ]
>
> in the gst binding.. Now it works!!