miniblog.

Python's GIL is well known, but many languages have limitations on multithreading (e.g. JS, Ocaml). Perhaps this is a consequence of C as a popular implementation language? A GIL could be less common when Rust is the implementation language.

The effectiveness of fuzzing, the limitations of current research, your best options today, and a worked example:

physical-cpu-count is a lovely example of small packages on npm doing one thing well. It's a cross-platform solution with clearly discussed limitations and design decisions regarding hyperthreading.