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Include note regarding #1222
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Extends the current coroutine intro to include a generalised warning regarding error fall throughs
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Ashthetik authored Oct 17, 2024
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Expand Up @@ -18,3 +18,5 @@ When using a `co_*` function such as `co_message_create`, the request is sent im
You may hear that coroutines are "writing async code as if it was sync", while this is sort of correct, it may limit your understanding and especially the dangers of coroutines. I find **they are best thought of as a shortcut for a state machine**, if you've ever written one, you know what this means. Think of the lambda as *its constructor*, in which captures are variable parameters. Think of the parameters passed to your lambda as data members in your state machine. When you `co_await` something, the state machine's function exits, the program goes back to the caller, at this point the calling function may return. References are kept as references in the state machine, which means by the time the state machine is resumed, the reference may be dangling: \ref lambdas-and-locals "this is not good"!

Another way to think of them is just like callbacks but keeping the current scope intact. In fact this is exactly what it is, the co_* functions call the normal API calls, with a callback that resumes the coroutine, *in the callback thread*. This means you cannot rely on thread_local variables and need to keep in mind concurrency issues with global states, as your coroutine will be resumed in another thread than the one it started on.

It is also worth noting that coroutines can lead to cases where errors may fall through and remain uncaptured, requiring the user to manually handle the error. These exceptions occur because callbacks cannot be used in their typical manner, which can be observed [in the following issue](https://github.com/brainboxdotcc/DPP/issues/1222) and the \ref coro-simple-commands "sample coroutine code".

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