Hi Florian, On Wed, Nov 23, 2022 at 11:48:06AM +0100, Florian Weimer wrote: > * Jason A. Donenfeld: > > > static void *vgetrandom_alloc(size_t *num, size_t *size_per_each, unsigned int flags) > > { > > unsigned long ret = syscall(__NR_vgetrandom_alloc, num, size_per_each, flags); > > return ret > -4096UL ? NULL : (void *)ret; > > } > > The traditional syscall function returns -1 on error and set errors, so > using unsing long and the 4096 is quite misleading. Not sure I have any idea at all whatsoever about what you're talking about. Firstly, the function you quoted is from the "sample userspace code" in the commit message, so it might not be code for the context you have in mind. Secondly, it's just doing the thing to figure out if the return value is an error value or a pointer. Were we in glibc, we'd write this as: return INTERNAL_SYSCALL_ERROR_P(r) ? NULL : (void *) r; Right? And if you look at the expansion of that glibc macro, it's just: #define INTERNAL_SYSCALL_ERROR_P(val) \ ((unsigned long int) (val) > -4096UL) So it looks like the same exact thing? The only difference I could see is that I assign it to a `unsigned long ret`, while glibc code tends to assign it to a `long r`? Is that the difference you're pointing out? Except that clearly doesn't matter because it just gets casted to unsigned by that macro anyway? Confused. Jason