How do I make any C++ library I make thread safe?

Question

First of all, I'm fairly experienced with C++ and understand the basics of threading and thread synchronization. I also want to write a custom memory allocator as a pet project of mine and have read that they should be thread-safe.

I understand what the term "thread-safe" means, but I have no idea on how to make C++ code thread-safe.

Are there any practical examples or tutorials on how to make code thread-safe?

In a memory allocator scenario, is it essentially ensuring that all mutating functions are marked as critical sections? Or is there something more to it?

Answer 1

Same as all threading issues: make sure that when one thread is changing something, no other thread is accessing it. For a memory allocation system, I would imagine you would need a way of making sure you don't allocate the same block of memory to 2 threads at the same time. Whether that is by wrapping the entire search, or by allowing multiple searches but locking when the allocation table is to be updated (which could then cause the result of the search to become invalid, necessitating another search) would be up to you.