SWIG: C++ to C#, pointer to pointer marshalling.
- by CaRT
I have some legacy code I want to port to C#. I cannot modify the C++ code, I just have to make do with what I'm given.
So, the situation. I'm using SwIG, and I came across this function:
void MarshalMe(int iNum, FooClass** ioFooClassArray);
If I ran SWIG over this, it wouldn't know what to do with the array, so it will create a SWIGTYPE_p_pFooClass. Fair enough!
C# code for this would look like
void MarshalMe(int iNum, SWIGTYPE_p_p_FooClass ioFooClassArray); // Not ideal!
There are some techniques for marshalling this kind of code correctly, so I tried a few of them:
%typemap(ctype) FooClass** "FooClass**"
%typemap(cstype) FooClass** "FooClass[]"
%typemap(imtype, inattributes="[In, Out, MarshalAs(UnmanagedType.LPArray)]") FooClass** "FooClass[]"
%typemap(csin) FooClass** "$csinput"
%typemap(in) FooClass** "$1 = $input;"
%typemap(freearg) FooClass** ""
%typemap(argout) FooClass** ""
This effectively creates a nicer signature:
void MarshalMe(int iNum, FooClass[] ioFooClassArray); // Looks good! Would it work?
However, when I try to run it, I get the following error:
{"Exception of type 'System.ExecutionEngineException' was thrown."}
Any ideas about the actual typemap?
