I ended up disabling the shared build, but I saw this pull and I thought I would comment:

• I like the exports macro but the the cmakelists should also use set_target_properties(mman PROPERTIES DEFINE_SYMBOL "MMAN_LIBRARY") to define MMAN_LIBRARY (and to enable export) when building the library.
• Secondly there should be a way to define an empty MMANSHARED_EXPORT when building a static library. From other examples I have seen one might define MMAN_DLL when both building and using a dll. This would require additional ifdefs for MMANSHARED_EXPORT and would also require CMakeLists to add_definitions(-DMMAN_DLL) when BUILD_SHARED_LIBS is true.
• For reference this is a pretty good example (ignore the gcc part, see #ifdef FOX_DLL) https://gcc.gnu.org/wiki/Visibility