llvm/clang/test/CodeGen/2005-03-05-OffsetOfHack.c

// RUN: %clang_cc1 %s -emit-llvm -o - 

struct s {
  unsigned long int field[0];
};

#define OFFS \
        (((char *) &((struct s *) 0)->field[0]) - (char *) 0)

int foo[OFFS];