/// @param ptr - A pointer to a byte to be filled in. Must be non-NULL.
/// @result - 0 if successful; -1 if not. Failure may be due to a
/// bounds violation or an implementation-specific error.
/// @param ptr - A pointer to a byte to be filled in. Must be non-NULL.
/// @result - 0 if successful; -1 if not. Failure may be due to a
/// bounds violation or an implementation-specific error.