Allocators and thread safety (and not only)

[g41797]

I gave up, but this post forced me return to the discussion.

Question:

@vkondratiuk

Why do we lock the mutex before and not after the Closure allocation? Isn’t allocating on heap - thread-safe?

Referenced code from std [Thread] Pool

And an answer

@AndrewKraevskii

It is only threadsafe if you using threadsafe allocator like std.heap.GeneralPurposeAllocator and std.heap.c_allocator.
Almost every other allocator in std is not threadsafe.

Also std.heap.GeneralPurposeAllocator can be configured to be not thread safe.

Do you see the problem here?

It’s the same problem, as problem of ThreadSafeAllocator - if allocator is not thread-safe, any wrapping with lock/unlock will not prevent non thread-safe usage.

With my proposal std code can check thread-safety of allocator and return error.

I know that

Compile errors are better than runtime crashes.

But

Runtime crashes are better than bugs.