Cgo linker errors on C constants

Cgo linker errors on C constants

I'm using cgo to wrap a C library and have run into a strange set of
linker errors. I've boiled the problem down to the following:
A file header.h contains
#ifndef HEADER_H
#define HEADER_H
#define CONSTANT1 ("")
#define CONSTANT2 ""
#define CONSTANT3 ((char*)0)
#define CONSTANT4 (char*)0