On 2023-05-31 22:18, Jonathan Wakely wrote: > On Wed, 31 May 2023 at 21:15, J.W. Jagersma via Gcc-help > <gcc-help@xxxxxxxxxxx> wrote: >> >> Hi all, >> >> In my cooperative scheduler I currently use a regular exception type for thread >> cancellation. But these tend to get eaten, for example by std::iosteam >> functions. >> >> Now I see those functions do catch and rethrow a __cxxabiv1::__forced_unwind >> type, and I presume such an object can be thrown via _Unwind_ForcedUnwind(). >> >> But how do you actually use it? > > You don't. It exists for pthread_kill, not for users. > >> Specifically, how is the exception supposed to >> be allocated, who is in charge of freeing it, > > The runtime does that as needed. > >> and how do you make sure it stops >> where you want it to? > > You can't, it can never be stopped. If it is caught and not rethrown > then the entire process is aborted. It must propagate to the initial > function that was executed in the thread, and then when it leaves that > function the thread is terminated. Okay, that's a bit unfortunate. But why is it exposed in a public header then if it's never supposed to be used by anyone? I understand doing something like this from user code is extremely messy, but... that's how these things are.
