But that only happens when the result is the same as if the instructions were ran synchronously, and synchronization primitives are still needed at the end of these sections.

Even if they weren't, the abstraction layer that you work at with Node is far, far above the point where you care about instruction reordering. If synchronicity is an inherent property of the process that you're implementing (e.g. you want to insert something in the database and then log an event) then no amount of shuffling will alleviate the fact that the logging has to happen after the database insertion.

Edit: the fact that deep down they reorder instructions is a bit scholastic, but if we are to go into these details, it's worth remembering that even the instruction reordering happens synchronously, and that even asynchronous events, like input from an off-chip peripheral, are treated synchronously. The turtles are synchronous all the way :-).

Haha yeah, sure. Reading the input from an IO device once it's been delivered is synchronous.

But IO is not handled in an synchronous fashion. If CPU cores just waited around idling until a hard drive is done fetching the data (for example), our computers would be very slow indeed.

That was my main point.

Ah, certainly. In a similar manner, what I meant is that oftentimes it's the process itself that's synchronous, and if the semantics of a language or a toolkit make it difficult to manipulate this sort of flow, people complain.

I've done too little work with Node to have a constructive opinion on it, but I've occasionally had similar complaints about Qt, which I've used a lot more. It uses a signal-slot paradigm where you basically say "when this event is triggered, this function gets called" (in a callback-like, but somewhat more powerful and flexible fashion). It's great for a lot of things, but makes it hard to read and reason about synchronous operations that have to be fit into this form.

Ultimately, though, people cope with it and write working software with it. I imagine it's the same with Node :-).

> What is async in JS and Node (unless you use the sync alternatives) is any kind of IO (disk, network). That is also async for the CPU.

The same statement is true of Erlang and Elixir, yet they manage to handle non-blocking async code without either of the daft callback/promise code styles of Javascript.

Even within the confines of async-capable languages, Node is one of the worse options.

I agree that CSP as in Erlang/Elixir or Go is way better for handling async behaviour.

Or clojure, whose flavor compiles down to JS.

As I said in my previous post, a CPU that doesn't respect barriers and reorders the instructions anyway is a bugged CPU, not a modern one.

If I need the database result before doing anything else then my code is inherently synchronous and it has an hard dependency on the database result. In that context making the DB call asynchronous and waiting for it is more complex than making a synchronous call and proceeding with the normal program flow. The most natural way to write an algorithm is to have everything synchronous and have a "simil-synchronisation" of the asynchronous program flow using an "async monad". And sadly I normally use C# 4.0 that still doesn't have the async construct borrowed from F#, so I'm stuck with tasks and continuations.

> And sadly I normally use C# 4.0 that still doesn't have the async construct borrowed from F#, so I'm stuck with tasks and continuations.

Do you know that the async/await constructs are just sugar for the Task class you have access on C# 4.0?

The C# implementation is a wrap/unwrap of the Task class, in F# it is using computation expressions to lift the synchronous code to an Async monad. The async construct is much easier to reason about, especially with nested tasks.