Visual Studio C++: When should I be using __declspec(dllimport)?

Question

I had a question about DLL building / linking in Visual Studio 2005 and later. Basically my understanding and experience is this:

To build a DLL, I specify the proje

Answer 1

Yes you would use __declspec(dllimport) and you generally have a macro that controls whether a source file either exports (if it's part of your DLL) or imports (if it's part of the using-executable) symbols.

In your DLL you can set a manifest constant to the build settings of some sort, say 'BUILDING_MY_DLL' and then create the macro like this within your header file:

#ifdef BUILDING_MY_DLL
#define MY_DLL_EXPORT __declspec(dllexport)
#else
#define MY_DLL_EXPORT __declspec(dllimport)
#endif

and then decorate your exported functions like this:

MY_DLL_EXPORT int func(int y);

You can also export entire classes this way too:

class MY_DLL_EXPORT InterestingClass
{
...
};