[CMake] UseSWIG creates module instead of shared library, which can't be dynamically loaded

[Mathieu Malaterre]

On Thu, Aug 6, 2009 at 2:46 PM, Mathieu
Malaterre<mathieu.malaterre at gmail.com> wrote:
> On Thu, Aug 6, 2009 at 2:27 PM, Stephen Roderick<kiwi.net at mac.com> wrote:
>> On Aug 6, 2009, at 06:02 , Mathieu Malaterre wrote:
>>
>>> On Wed, Aug 5, 2009 at 6:55 PM, Stephen Roderick<kiwi.net at mac.com> wrote:
>>>>
>>>> The existing UseSWIG.cmake file creates a MODULE and not a SHARED
>>>> library.
>>>> The module is unuseable by any program trying to load dynamic libraries
>>>> (eg
>>>> wrapped Java). The attached patch fixes this problem for our situations.
>>>> Demonstrated on both Mac OS X Leopard and Ubuntu Jaunty.
>>>>
>>>> Is this a known issue? I searched what I could of the list and the 'net,
>>>> and
>>>> couldn't find anything on this.
>>>
>>> No, you are confusing the C++ library and the Java binding. Instead:
>>>
>>> ADD_LIBRARY(foo SHARED ${foo_SRCS}) # the actual shared lib
>>> SWIG_ADD_MODULE(foojni java foo.i)
>>> SWIG_LINK_LIBRARIES(foojni foo
>>>  ${JNI_LIBRARIES}
>>> )
>>>
>>> The next time you will want to create -say- a python module you'll
>>> simply link to your *shared C++* library:
>>>
>>> SWIG_ADD_MODULE(foopython python foo.i)
>>> SWIG_LINK_LIBRARIES(foopython foo
>>>  ${PYTHON_LIBRARIES}
>>> )
>>
>> Unfortunately, that is what we currently have.
>>
>> <code>
>>  ADD_LIBRARY(MyInterfaceCpp ...)
>>
>>  Find_Package(SWIG REQUIRED)
>>  Find_Package(JNI REQUIRED)
>>  INCLUDE(UseSWIG)
>>  INCLUDE_DIRECTORIES(${JAVA_INCLUDE_PATH} ${JAVA_INCLUDE_PATH2})
>>
>>  SET_SOURCE_FILES_PROPERTIES(MyInterface.i PROPERTIES CPLUSPLUS 1)
>>  # compile swig with package flag
>>  SET(CMAKE_SWIG_FLAGS -package x.y.z)
>>
>>  SWIG_ADD_MODULE(MyInterface java MyInterface.i)
>>  SWIG_LINK_LIBRARIES(MyInterface
>>        MyInterfaceCpp ...)
>> </code>
>>
>> The failure comes when you try to load the SWIG-output, JNI library from
>> within java, using something like
>> <code>
>>        static {
>>                System.loadLibrary("MyInterface");
>>        }
>> </code>
>>
>> With a module in a "MyInterface.so" file (what SWIG currently outputs), the
>
> No. On Linux 'lib' is always preprended, even for MODULE. I am not
> sure about MacOSX.
>
>> above call fails on both Mac OS X and Linux. They both need a correctly
>> named dynamic library, hence the patch.
>
> I have been using this in gdcm and it works fine on Linux:
>
> http://gdcm.svn.sf.net/viewvc/gdcm/trunk/Wrapping/Java/gdcm.i?r1=5779&r2=5799

My bad... I forgot that SWIG stuff always override the 'lib' setting,
hence you have to revert it:

http://gdcm.svn.sf.net/viewvc/gdcm/trunk/Wrapping/Java/CMakeLists.txt?view=markup

See comments:
...
 IF(UNIX)
   SET_TARGET_PROPERTIES(${SWIG_MODULE_gdcmjni_REAL_NAME} PROPERTIES
PREFIX "lib")
 ENDIF(UNIX)
...

I think this comes from the SWIG module initially designed based on
the python requirement where '_' would be preprended before the actual
lib name.

Sorry for the confusion.
-- 
Mathieu
http://mathieumalaterre.com