[libc-commits] [libc] [libc] Add fuzzers for `memcpy` and `memset` (PR #90591)

[Guillaume Chatelet via libc-commits]

gchatelet wrote:

So as discussed offline, I turned the fuzzers into tests and fixed the bug in this patch to avoid breaking the build bots.
Contrary to what I originally thought [the tests do exercise the software prefetching code](https://github.com/llvm/llvm-project/blob/c7c5666aac543a49b485a133f4a94865e2613a43/libc/src/string/CMakeLists.txt#L603-L604).


https://github.com/llvm/llvm-project/pull/90591