According to <http://man7.org/linux/man-pages/man2/getrandom.2.html>, getrandom() returns no more than 32 MiB as an int on Linux. Doesn’t that mean you can rely on syscall()’s long return value fitting in an int? Maybe just cast n = (int)sycall(...) to be explicit.

But it does make sense to cap n to LONG_MAX just in case there is some strange platform where it matters :)