What the __declspec(dllexport/import) is used for?

[Vida Marcell]

I'm currently working with dlls in c++, and the first thing i noticed is this function __declspec(dllexport/import). There isn't too much explanations for it, but i think, the export if for making a function usable by other software that can acess the dll file, and the import is for the software to call a function from the dll? Am i correct?

[reepblue]

Correct, It's also best to have one Macro for both import and export and define a lib preprocessor define for the library's project like so. 

#if defined (INPUTSYSTEM_LIB)
    #define INPUTSYTEM_API DLL_EXPORT
    #define INPUTSYTEM_API_GLOBAL DLL_EXPORT_GLOBAL
#else
    #define INPUTSYTEM_API DLL_IMPORT
    #define INPUTSYTEM_API_GLOBAL DLL_IMPORT_GLOBAL
#endif

Then you make write your headers as so.

class INPUTSYTEM_API IInputDriver
{
public:
	IInputDriver() {};
    virtual ~IInputDriver() {};
};

INPUTSYTEM_API_GLOBAL void Init();

Working with DLLs can be a frustrating experience if your source tree isn't set up properly. You might want to consider public and private headers and expose the minimum to the other projects.