[pypy-dev] Fwd: cffi dlopen

[Roshan Cherian]

Hi Armin/Maciej,

Thanks for the reply, following the code sample I wrote up the following:

from cffi import FFI

ffi = FFI()


ffi.set_source("_ical_cffi_ext",

    """ // passed to the real C compiler

        #include <libical/ical.h>

    """,

    include_dirs=['./include'],    # where ical.h is

        libraries=['ical'],

        library_dirs=['./lib'],)   # or a list of libraries to link with


ffi.cdef("""     // some declarations from the man page


        typedef struct icalcomponent_impl icalcomponent;


        typedef struct icalproperty_impl icalproperty;


        typedef ... icalparameter;


        typedef struct icalvalue_impl icalvalue;


        typedef ... icaltimezonechange; //really typedef struct
_icaltimezonechange
icaltimezonechange;


        struct _icaltimezonechange {

            int          utc_offset;

            int          prev_utc_offset;

            int          year;          /**< Actual year, e.g. 2001. */

            int          month;         /**< 1 (Jan) to 12 (Dec). */

            int          day;

            int          hour;

            int          minute;

            int          second;

            int          is_daylight;

        };


""")


if __name__ == "__main__":

    ffi.compile()


_icaltimezonechange is opaque as its in src/libical/icaltimezone.c a c file
and not in in ical.h. However this struct is required for my purpose.
However when it compiles I do get errors like:


_ical_cffi_ext.c:455: error: dereferencing pointer to incomplete type

_ical_cffi_ext.c:457: error: invalid use of undefined type 'struct
_icaltimezonechange'

_ical_cffi_ext.c:458: error: dereferencing pointer to incomplete type

_ical_cffi_ext.c:468: error: invalid application of 'sizeof' to incomplete
type 'struct _icaltimezonechange'

_ical_cffi_ext.c:468: error: initializer element is not constant

_ical_cffi_ext.c:468: error: (near initialization for
'_cffi_struct_unions[2].alignment')


Can I know what should be done for these cases?


Thanks,

-Roshan

On Tue, Sep 15, 2015 at 8:17 AM, Armin Rigo <arigo at tunes.org> wrote:

> Hi Roshan,
>
> On Tue, Sep 15, 2015 at 5:01 PM, Roshan Cherian <cherian.rosh at gmail.com>
> wrote:
> >>>>> libical = ffi.dlopen(ctypes.util.find_library('ical'))
> >>>>>
> libical.ical_set_unknown_token_handling_setting(libical.ICAL_ASSUME_IANA_TOKEN)
> >
> > I get an error: AttributeError: ical_set_unknown_token_handling_setting
>
> This means the library file was found, but it doesn't contain any
> symbol of the name "ical_set_unknown_token_handling_setting".  It may
> be because such a name is actually a macro.  In that case you can't
> use ffi.dlopen().
>
> You should look at ffi.set_source() instead (and *not* ffi.verify();
> Maciej probably mentioned this by mistake, it is now called
> set_source()).
>
> > I haven't tried out ffi.verify I am not sure how to load a shared lib
> using
> > ffi.verify, I am sorry if my understanding is wrong.
>
> See
> http://cffi.readthedocs.org/en/latest/overview.html#real-example-api-level-out-of-line
> .  In your case you need:
>
> ffi.set_source("_ical_cffi",
>     """ #include <ical.h>
>     """,
>     include_dirs=['./include'],    # or where ical.h is
>     libraries=['ical'],
>     library_dirs=['./lib'],             # or where libical.so is
> )
>
> You also need the same ffi.cdef() as you use now, and ffi.compile() as
> shown in the example.  The ffi.cdef() can use the syntax ``...``
> (dot-dot-dot) in many places when it is combined with
> ffi.set_source().  See the rest of the documentation section for more.
>
>
> A bientôt,
>
> Armin.
>
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