Why microsoft linker modifies decorated export names?

Question

I'm trying to make a proxy dll using the "wrappit" tool as recommended here. The tools "wrappit" creates as .cpp correctly:

// ??0CFileFormat@@QAE@XZ
extern "C" __declspec(naked) void __stdcall __E__0__()
    {
    __asm
        {
        jmp p[0*4];
        }
    }

// ?GetSkipListingForSPlanner@EnvironVar@@SAKXZ
extern "C" __declspec(naked) void __stdcall __E__262__()
    {
    __asm
        {
        jmp p[262*4];
        }
    }

as accompanying .def file:

EXPORTS
??0CFileFormat@@QAE@XZ=__E__0__ @1
?GetSkipListingForSPlanner@EnvironVar@@SAKXZ=__E__262__ @263

But after I have built the resulting library, all the names of the exported functions in the dll built appear to be truncated right as the description of the parameters begins. So ??0CFileFormat@@QAE@XZ turns in ??0CFileFormat, ?GetSkipListingForSPlanner@EnvironVar@@SAKXZ turns into ?GetSkipListingForSPlanner@EnvironVar and so on. As a result, my proxy dll does not load due to the lack of necessary exports. Why this happens and what should I do to fix it?