On Wed, 31 May 2023 at 21:24, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > > On Wed, 31 May 2023 at 21:23, J.W. Jagersma <jwjagersma@xxxxxxxxx> wrote: > > > > 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. > > Why not just use pthread_kill(0) if you want a __forced_unwind exception? Sorry, I mean pthread_kill(pthread_self(), SIGTERM) or similar.
