[codeflo]

Rust doesn’t have initializers in the C++ sense. And I mean, even in C++ many classes like shared_ptr or even lock_guard have constructors that don’t acquire the resources yet. When the resource is acquired is an API design concern; the important part is where it’s released.

[jolux]

This sounds like an argument that C++ isn't RAII.

[somedudetbh]

C++ _isn't_ RAII. RAII is a design pattern you can apply, leveraging C++ language features, in C++ in certain cases to avoid a certain class of bugs.

[jolux]

Well sure but I would assume the pattern would be consistently implied in the standard library, no?

[jeffbee]

The standard library necessarily has broad coverage of many use cases. That's why not every constructor of lock_guard acquires the lock. It's a completely legitimate use case that your thread happens to have a lock and wishes to use the end of lifetime of a lock_guard to release it. It's the same reason that you can construct a unique_ptr from an object that was allocated with new instead of with make_unique. Also, it's perfectly analogous to Go's `defer mu.Unlock()`.

[beaukin]

I'm not an expert, but I would so no, it's not. The point of learning to implement with RAII, in the context of C++, is so that one will apply it to use C++ in a more resource safe way. It will help avoid the bugs that the language will inherently allow if the programmer is not being otherwise being careful.