#ifdef __SUNPRO_C
static void mark(C_word *x) { \
  C_word *_x = (x), _val = *_x; \
  if(!C_immediatep(_val)) really_mark(_x); \
}
#else
# define mark(x)				\
  C_cblock                                      \
  C_word *_x = (x), _val = *_x;                 \
  if(!C_immediatep(_val)) {                     \
    if (C_in_stackp(_val) || C_in_heapp(_val))  \
      really_mark(_x);                          \
  }                                             \
  C_cblockend
#endif