Async/Await is finally back in Zig

Is it time now to say that async was a mistake, a-la C++ exceptions? The recent futurelock discussion[1] more or less solidified for me that this is all just a mess. Not just that one bug, but the coloring issue mentioned in the blog post (basically async "infects" project code requiring that you end up porting or duplicating almost everything -- this is especially true in Python). The general cognitive load of debugging inside out code is likewise really high, even if the top-level expression of the loop generator or whatever is clean.

And it's all for, what? A little memory for thread stacks (most of which ends up being a wash because of all the async contexts being tossed around anyway -- those are still stacks and still big!)? Some top-end performance for people chasing C10k numbers in a world that has scaled into datacenters for a decade anyway?

Not worth it. IMHO it's time to put this to bed.

[1] No one in that thread or post has a good summary, but it's "Rust futures consume wakeup events from fair locks that only emit one event, so can deadlock if they aren't currently being selected and will end up waiting for some other event before doing so."

I really wish people would get over the coloring meme.

Knowing if a function will yield the thread is actually extremely relevant knowledge you want available.

Except function colouring is a symptom of two languages masquerading as one. You have to choose async or sync. Mixing them is dangerous. It’s not possible to call an async function from sync. Calling sync functions from async code runs the risk of holding the run lock for extended periods of time and losing the benefit of async in the first place.

I don’t have anything against async, I see the value of event-oriented “concurrency”, but the complaint that async is a poison pill is valid, because the use of async fundamentally changes the execution model to co-operative multitasking, with possible runtime issues.

If a language chooses async, I wish they’d just bite the bullet and make it obvious that it’s a different language / execution model than the sync version.