#define MY_MPI_ENUM MPI_INT // or define some other way
static const MPI_Datatype my_mpi_enum MPICH_ATTR_TYPE_TAG(MyEnum) = MY_MPI_ENUM;

Of course the above does not work because the new definition masks the old one, so all the normal 'int' uses are hidden. Unfortunately, the annotation syntax requires compile-time constants, which are not accessible to me.

Is there any hope for something like this, or do I have to choose between (a) ugly cast at all MPI call points and (b) make MY_MPI_ENUM a variable so that the compiler can't check it statically?