Looking at Unity made me understand the point of C++ coroutines

Post by mgaunard » Fri, Mar 27, 2026, 9:04 PM UTC

spacechild1 wrote: post #175

mgaunard wrote: post #173

Earlier quoted context omitted.

Using shared_ptr everywhere is an antipattern. The whole point of controlling the capture is controlling the memory layout, which is what C++ is all about. Even with Asio, you don't really have to do this. It's just the style the examples follow, and Asio itself isn't necessarily the best design.

With callbacks you have to make sure that your data persists across the function calls. This necessarily requires more heap allocations (or copies) than in a coroutine where most data can just live on the stack.

Post by mgaunard » Sun, Mar 29, 2026, 7:33 PM UTC

spacechild1 wrote: post #182

mgaunard wrote: post #181

Earlier quoted context omitted.

A coroutine doesn't do anything more than a callback does -- it's just syntactic sugar. The default behaviour of many asynchronous systems is to extend the lifetime of context data until all the asynchronous handlers have run. You can also just bind them to the resource instead which is arguably more elegant, but which depends on how cancellation is implemented.

Any data that needs to survive across several callback invocations requires shared ownership. This means that the data must be allocated on the heap and probably also requires reference counting. With lambdas it's also easy to make mistakes, e.g. by capturing variables on the stack by reference. In a coroutine everything can just live on the stack because the stack frame itself is kept alive across the asynchronous f…

Post by mgaunard » Tue, Mar 31, 2026, 1:13 PM UTC

spacechild1 wrote: post #184

mgaunard wrote: post #183

Earlier quoted context omitted.

Not necessarily, I already explained how (resource binding). Close the socket, all handlers are cancelled, context can be freed immediately. The socket owns the data.

> The socket owns the data. What if there's more than one socket involved?

Post by HarHarVeryFunny » Fri, Apr 03, 2026, 8:31 PM UTC

LatencyKills wrote: post #177

HarHarVeryFunny wrote: post #171

Earlier quoted context omitted.

I said used, as in used in your everyday life, by interacting with computer systems whose backend implementations you are blissfully ignorant of. But yeah, if you want to win arguments then arguing against yourself and your own hallucinations, is in your case the best way to go.

Um... you might want to look at my profile. In addition to working at MS and Apple for two decades (where I touched everything from firmware, ring-0, and ring-3), I was on the team that created SoftICE [0]: the first commercial ring-0 debugger for Windows. I also created the automated deadlock detector for BoundsChecker [1], which requires an in-depth understanding of operating system internals. > computer systems wh…

Post by HarHarVeryFunny » Sat, Apr 04, 2026, 12:33 PM UTC

LatencyKills wrote: post #188

HarHarVeryFunny wrote: post #187

Earlier quoted context omitted.

> You wrote a "C++ framework" that runs in the "backend" of a "computer system"? Do I have that right? Probably not. You seem to be struggling with technical language.

See? I have no problem sharing/discussing what I've built. Throughout this entire thread they only thing you've done is bullshit. And again, remember that this started because you thought coroutines were "intimidating" while trying to mansplain how they worked to someone who literally built that functionality. But sure... let's keep going while you do nothing but whine without displaying any technical acumen. This is…