On Sep 24, 2008, at 5:47 AM, Julien Michel wrote:
Werner Smekal a écrit :
Hi,
maybe you forgot to export symbols?
http://www.cmake.org/Wiki/BuildingWinDLL
Dear Werner,
Thank you, I did search the cmake Wiki for something like that, but I
did not manage to find this page. I think we are exporting/importing
our
symbols in most of the case, but I did not know that visual will
simply
not build any dll if there is no exported symbol.
This lead me to another question:
In the wiki page, it is suggested to do the following:
#if defined (_WIN32)
#if defined(MyLibrary_EXPORTS)
#define MYLIB_EXPORT __declspec(dllexport)
#else
#define MYLIB_EXPORT __declspec(dllimport)
#endif /* MyLibrary_EXPORTS */
#else /* defined (_WIN32) */
#define MYLIB_EXPORT
#endif
But in this piece of code, the case were we build static libraries
under
windows is not handled. This means that we will import/export symbols
even if we build static libraries, and this seems to break the
compilation, leading to "undefine reference to declspec(dllimport)
xxx"
when trying to link against the library. I did look at the export
sections of other libraries and they seem to handle this static case
by
removing the __declspec(dllexport)/__declspec(dllimport). What is the
right thing to do here ?
Thank you for your reply,
Best regards,
Julien
--
Julien,
Funny. I wrote that wiki entry and it was a bit different when I
first wrote it but after some feedback I changed the code slightly
and looking back at the code I don't think it would work correctly for
the static case.
Like Werner I actually use a second definition in my code:
#if defined (_WIN32) && defined (BUILT_AS_DYNAMIC_LIB)
#if defined(MyLibrary_EXPORTS)
#define MYLIB_EXPORT __declspec(dllexport)
#else
#define MYLIB_EXPORT __declspec(dllimport)
#endif /* MyLibrary_EXPORTS */
#else /* defined (_WIN32) */
#define MYLIB_EXPORT
#endif
#endif /* _MyLibrary_DLLDEFINES_H_ */
Then in the cmake code you do something like:
# Allow the developer to select if Dynamic or Static libraries are built
OPTION (BUILD_SHARED_LIBS "Build Shared Libraries" OFF)
# Set the LIB_TYPE variable to STATIC
SET (LIB_TYPE STATIC)
IF (BUILD_SHARED_LIBS)
# User wants to build Dynamic Libraries, so change the LIB_TYPE
variable to CMake keyword 'SHARED'
ADD_DEFINITIONS(-DBUILD_AS_DYNAMIC_LIBRARY)
SET (LIB_TYPE SHARED)
ENDIF (BUILD_SHARED_LIBS)
Which should help take care of that case for you.
Mike
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