On Fri, 14 Apr 2023 at 00:44, Edward Catmur <ecatmur@googlemail.com> wrote:
>> Warning users that these things don't work in coroutines seems like a
>> palatable solution to me.
>
>
> It seems like a non-solution to me. Users will do it anyway, then get confused and complain when it doesn't work. Coroutine libraries will come up with solutions like the above, but independently and without interoperability, so if you're using the folly scope guards you have to use folly coroutines and vice versa, and the same for boost etc.
>
> The thing is, it is possible for scope guard destructors to detect how they were called. We just have to give up composability, which honestly doesn't seem like that much of an issue - why would you want to put a scope guard inside another object or in dynamic storage?
To give RAII semantics to types that don't have them internally,
without having to write holder types. If that's the price of getting
coroutines to work, to lose the ability to do that, then you can burn
coroutines for all I care.
If it's for RAII, then plain scope_guard should be fine (even if a bit misused; a class type is not a scope). scope_success and scope_failure would not make much sense as data members unless you're writing another success/failure scope guard class (what I meant by composability).