GETENV_UNSIGNED
&read_size, sizeof(*data), GETENV_UNSIGNED) != 0) {
sizeof(int), GETENV_UNSIGNED) == 0)
sizeof(long), GETENV_UNSIGNED) == 0)
sizeof(uint8_t), GETENV_UNSIGNED) == 0)
sizeof(uint16_t), GETENV_UNSIGNED) == 0)
sizeof(uint32_t), GETENV_UNSIGNED) == 0)
sizeof(uint64_t), GETENV_UNSIGNED) == 0)