These utilities are for handling extents (arrays and pointers) in C and C++.
T arg[static N]functionality (“sized at least `N` large” hint).
Expands to the proper notation for C compilers, and expands to nothing for C++ compilers. It is meant to be used as in the declaration:
void f(T arg[ZTD_PTR_EXTENT(N)]);.
... – [in] An expression which computes the intended size of the pointer argument.