memset_s was added to C11 in an optional annex, and my understanding is that there are zero platforms that actually implement it. (Microsoft implemented an early draft of Annex K that doesn't actually include memset_s.)
Most libc's added an insecure version of memset_s, doing only the above discussed compiler-barrier, but not a memory-barrier, which is needed for Spectre, broken HW. The default memset should do the compiler-barrier. But unfortunately you cannot talk with libc maintainers about security. Too much arrogance. Thanks to this Redhat article for supporting the user-base on this.
You can use my safeclib, which implements the Annex K extensions.