Choose the size representation that bests fits your use case:

  // Put this in header to help user calculate allocation needs but hide size from user
  size_t LIBNAME_alloc_size(param1, param2, ...);

  // Put this in the header to hide the size from user code but allow inlined size calculations
  extern const size_t LIBNAME_ALLOC_X;

  // Put this in the header to make size known to user (for static const allocation)
  #define LIBNAME_ALLOC_Y ((size_t)42)