Binding a C++ _TCHAR to a C# string in a SWIG interface

Question

I have some old C++ code that I'm trying to compile as a DLL so that it can be used in a C# Xamarin.IOS project, using SWIG to create bindings for a wrapper between the C++ and the C#.

So far I have been able to get it working for all methods that take or return int, double, or bool parameters, but I'm stuck with how to deal with _TCHARs.

Where the C++ code uses _TCHARs as the parameter types, no matter what I've tried in the SWIG interface file, the C# parameters for any methods which should take a string are coming up as SWIGTYPE_p__TCHAR, which is as far as I can tell is what SWIG produces when it doesn't know what it should use.

I'm sure that this should be a case of using the right typemap in the SWIG interface file, but nothing I've tried so far has worked, any suggestions would be much appreciated!

Answer 1

In the end, the maintainer of the C++ code changed his code to use standard chars instead of _TCHARs and I have managed to get this working.

Answer 2

TCHAR is a preprocessor defined constant that is set at compile time windows.h based on the UNICODE preprocessor constant: if UNICODE is defined, it will either be wchar_t, otherwise it will be char. But you have to choose one: is your module unicode or ascii? If former, you should set UNICODE as part of your SWIG command:

swig -DUNICODE -c++ -csharp example.i

else

swig -c++ -csharp example.i

Since you are presumably doing latter, and getting this error, you probably forgot to %include <windows.i> after the preamble and before your declarations (if you have trouble, show your .i then I can be more specific).