[CMake] Building either shared or static version of a library on Windows

[Michael Jackson]

There are lots of different ways to do this. The following is an example of what *I* do.
----- In my CMakeLists.txt file I have this
 set(DREAM3DLib_BUILT_AS_DYNAMIC_LIB)
IF (BUILD_SHARED_LIBS)
    set(DREAM3DLib_BUILT_AS_DYNAMIC_LIB 1)
    IF (WIN32)
        ADD_DEFINITIONS("-DDREAM3DLib_BUILT_AS_DYNAMIC_LIB")
    ENDIF (WIN32)
ENDIF (BUILD_SHARED_LIBS)

----- In a Header file Define this

 /* Cmake will define DREAM3DLib_EXPORTS on Windows when it
configures to build a shared library. If you are going to use
another build system on windows or create the visual studio
projects by hand you need to define DREAM3DLib_EXPORTS when
building the MXADatModel DLL on windows.
*/

#if defined (DREAM3DLib_BUILT_AS_DYNAMIC_LIB)

  #if defined (DREAM3DLib_EXPORTS)  /* Compiling the MXA DLL/Dylib */
    #if defined (_MSC_VER)  /* MSVC Compiler Case */
      #define  DREAM3DLib_EXPORT __declspec(dllexport)
      #define EXPIMP_TEMPLATE
    #elif (__GNUC__ >= 4)  /* GCC 4.x has support for visibility options */
      #define DREAM3DLib_EXPORT __attribute__ ((visibility("default")))
    #endif
  #else  /* Importing the DLL into another project */
    #if defined (_MSC_VER)  /* MSVC Compiler Case */
      #define  DREAM3DLib_EXPORT __declspec(dllimport)
      #define EXPIMP_TEMPLATE extern
    #elif (__GNUC__ >= 4)  /* GCC 4.x has support for visibility options */
      #define DREAM3DLib_EXPORT __attribute__ ((visibility("default")))
    #endif
  #endif
#endif

/* If DREAM3DLib_EXPORT was never defined, define it here */
#ifndef DREAM3DLib_EXPORT
  #define DREAM3DLib_EXPORT
  #define EXPIMP_TEMPLATE
#endif

Hope that helps. There is also a wiki entry on this topic on the CMake Wikie. "Building a DLL for Linux Devs" which might help also.

___________________________________________________________
Mike Jackson                    Principal Software Engineer
BlueQuartz Software                            Dayton, Ohio
mike.jackson at bluequartz.net              www.bluequartz.net

On Jan 15, 2013, at 11:09 AM, Bogdan Cristea wrote:

> Hi
> 
> My exports header file for a C/C++ project has the following
> definitions:
> 
> #if defined(WIN32) || defined(WIN64)
>  #ifndef LIB_EXPORT
>    #ifdef lib_EXPORTS
>      #define LIB_EXPORT __declspec(dllexport)
>    #else
>      #define LIB_EXPORT __declspec(dllimport)
>    #endif
>  #endif
> #endif
> 
> where lib_EXPORTS is automatically defined by cmake when the shared
> library is build. However, this aproach works only with a shared
> library, when I try to build the static version I get a compilation
> error with Visual Studio 2010, since LIB_EXPORT is
> __declspec(dllimport).
> 
> An workaround is to define in the CMakeLists.txt file another compiler
> variable when the static version is build and set in the exports header
> LIB_EXPORT to an empty define when the static library is build. However,
> this must be done each time a program is build with the static version
> of the library, which makes this approach cumbersome.
> 
> Is there a better way to define the exports header file in order to be
> able to build and compile with other program either the shared or the
> static version of a library  ?
> 
> thanks
> Bogdan
> 
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