CMake/Tests/SimpleInstallS2/lib4.h

#ifdef _WIN32
#  ifdef test4_EXPORTS
#    define CM_TEST_LIB_EXPORT  __declspec( dllexport )
#  else
#    define CM_TEST_LIB_EXPORT  __declspec( dllimport )
#  endif
#else
#  define CM_TEST_LIB_EXPORT 
#endif

CM_TEST_LIB_EXPORT float Lib4Func();