Comment by jdw64
10 hours ago
It seems like the thread_local CacheIndex only determines which cache to use, but it doesn't actually guarantee thread safety for concurrent access to the HashLifeCache itself. What would be a good solution for this?
Should I use a mutex for each cache instance? As a beginner developer, my guess is that the original author assumes data races won't occur based on the execution timing. However, I'm really not sure if that assumption is actually correct/safe.
In my view, thread_local is a bit of a code/design red flag. I didn't read the entire code in this case to see whether the thread_local use is warranted or not, though.
a thread_local is just a global variable. Mutable global variables are of course bad, but in this case the threadindex is immutable once created, so it is perfectly fine.
Yes, technically it is of course fine, just as a design I find use of thread_local is more of an afterthought than something I'd prefer.