How to expose STL list over DLL boundary?

Question

I have a DLL which needs to access data stored in STL containers in the host application. Because C++ has no standard ABI, and I want to support different compilers, the interf

Answer 1

You can pass stl objects between DLLs and support different compilers if you are careful where you instantiate each stl type. You need some intelligent "DLLEXPORT" macros -- I use the following set to successfully support VC and gcc.

#ifdef WIN32
#ifdef MYDLLLIB_EXPORTS      // DLL export macros
#define MYDLLLIB_API __declspec(dllexport)
#define MYDLLLIB_TEMPLATE
#else
#define MYDLLLIB_API __declspec(dllimport)
#define MYDLLLIB_TEMPLATE extern
#endif
#else                       // Not windows --- probably *nix/bsd
#define MYDLLLIB_API
#ifdef MYDLLLIB_EXPORTS
#define MYDLLLIB_TEMPLATE
#else
#define MYDLLLIB_TEMPLATE extern
#endif
#endif // WIN32

When compiling your DLL, define MYDLLLIB_EXPORTS. In the DLL you can then instantiate each stl type you wish to use, for example, lists or vectors of strings

MYDLLLIB_TEMPLATE template class MYDLLLIB_API std::vector;
MYDLLLIB_TEMPLATE template class MYDLLLIB_API std::list;

Consumers of your DLL (who don't have MYDLLLIB_EXPORTS defined) will then see

extern template class __declspec(dllimport) std::vector;

and use the binary code exported from your DLL instead of instantiating their own.