Unix and Windows use completely different paradigms for run-time loading of code. Before you try to build a module that can be dynamically loaded be aware of how your system works.

In Unix a shared object (.so) file contains code to be used by the program and also the names of functions and data that it expects to find in the program. When the file is joined to the program all references to those functions and data in the file's code are changed to point to the actual locations in the program where the functions and data are placed in memory. This is basically a link operation.

In Windows a dynamic-link library (.dll) file has no dangling references. Instead an access to functions or data goes through a lookup table. So the DLL code does not have to be fixed up at runtime to refer to the program's memory; instead the code already uses the DLL's lookup table and the lookup table is modified at runtime to point to the functions and data.

In Unix there is only one type of library file (.a) which contains code from several object files (.o). During the link step to create a shared object file (.so) the linker may find that it doesn't know where an identifier is defined. The linker will look for it in the object files in the libraries; if it finds it it will include all the code from that object file.

In Windows there are two types of library a static library and an import library (both called .lib). A static library is like a Unix .a file; it contains code to be included as necessary. An import library is basically used only to reassure the linker that a certain identifier is legal and will be present in the program when the DLL is loaded. So the linker uses the information from the import library to build the lookup table for using identifiers that are not included in the DLL. When an application or a DLL is linked an import library may be generated which will need to be used for all future DLLs that depend on the symbols in the application or DLL.