redirect stdout in C++

Hi,
I use RealView MDK_ARM

I want to define a functionpointer in the __FILE struct (stdio.h).
By changing this functionpointer in my mainprogram I can redirect stdout to some device.

To do this I changed the file retarget to following

#include <stdio.h>

extern "C" {
        struct __FILE {
                int handle;
                int *(*stdoutProc)(int ch);                     //THIS IS THE FUNCTIONPOINTER I CREATED
        };

        FILE __stdout;
        FILE __stdin;


        InitStdOut(int *MyStdOut(int Ch)) {
          __stdout.stdoutProc = MyStdOut;
        }

        int fputc (int ch, FILE *f) {
          __stdout.stdoutProc(ch);
          return(ch);
        }
} //extern C

I did not test the code, so maybe the code doesn't do the thing I want to do, but however I can compile it without errors !

When I rename all the files to *.cpp, to use the compilers C++ extentions, I have the error (at the line FILE __stdout;) error #70: incomplete type is not allowed

How can I add a functionpointer to the __FILE struct in C++ environment ?

Thank you