Bridging unmanaged and managed classes

Question

I have a native C++ class that is exported to a Win32 Dll:

class __declspec(dllexport) Manager { ... }

The Dll is created successfully. Let's call it Unmanaged.dll.

I want to use this class in a .Net application. Therefore, I decided to create managed C++ wrapper classes. So I created a new CLR class library where I set Unmanaged.dll as an input to the linker.

When compiling the managed dll I get the following error:

fatal error LNK1107: Invalid or corrupt file: cannot read at 0x318. (Unmanaged.dll in project ManagedBridge)

Both projects are set to compile to x64. DLL Export Viewer shows the class' constructor and methods. So the Dll seems to be fine.

Is there something I am missing?

Answer 1

You cannot pass a DLL to the linker, it has no idea what to do with it. A DLL is in general not suitable to help a linker determine that the DLL contains the functions you call. Exports from a DLL can be a number of a name. It being a number (an "ordinal") is a problem, the linker will not know how to map the number to the identifier name. And the name does not have to match either, names are commonly simplified with their name decoration removed.

You must instead tell the linker about the DLL's import library. Which has more information, including the ordinal to name mapping and the original decorated name that the compiler used. The import library is a .lib that was created when you linked the DLL. You will find it back in the DLL project's build directory. Add its path to the linker's Additional Dependencies setting.