[Lldb-commits] [PATCH] D44056: [lldb] Fix "code unreachable" warning in HostThreadPosix::Cancel

[Pavel Labath via Phabricator via lldb-commits]

labath added inline comments.


================
Comment at: source/Host/posix/HostThreadPosix.cpp:44
   if (IsJoinable()) {
 #ifndef __ANDROID__
 #ifndef __FreeBSD__
----------------
xiaobai wrote:
> labath wrote:
> > xiaobai wrote:
> > > aprantl wrote:
> > > > What about:
> > > > ```
> > > > #ifdef __ANDROID__
> > > >     error.SetErrorString("HostThreadPosix::Cancel() not supported on Android");
> > > > #else
> > > > #ifdef __FreeBSD__
> > > >     int err = ::pthread_cancel(m_thread);
> > > >     error.SetError(err, eErrorTypePOSIX);
> > > > #else
> > > >     llvm_unreachable("someone is calling HostThread::Cancel()");
> > > > #endif
> > > > #endif
> > > >   }
> > > >   return error;
> > > > }
> > > > ```
> > > I agree with Adrian's suggestion, but I would add that you can remove one of the `#endif` if you use `#elif defined(__FreeBSD__)` instead of an `#else` + `#ifdef __FreeBSD__`.
> > I think we can just unify the __ANDROID__ and __FreeBSD__  cases (turn both into unreachable). We only run lldb-server on android, and there we're mostly single-threaded, so there shouldn't be any thread cancelling going on anyway...
> I don't think we can make the FreeBSD case unreachable (if I understand the code correctly) since that's the one case when `::pthread_cancel` is actually getting called.
> 
> If we can make the `__ANDROID__` case unreachable, this would very easily turn into
> ```
> #if defined(__FreeBSD__) || defined(__NetBSD__)
>     int err = ::pthread_cancel(m_thread);
>     error.SetError(err, eErrorTypePOSIX);
> #else
>     llvm_unreachable("Someone is calling HostThreadPosix::Cancel()");
> #endif
> ```
> 
> I'm somewhat unfamiliar with how exactly this code is used on android. If I understand correctly, you're saying it's used in lldb-server and you meant that lldb-server is mostly single threaded so this code shouldn't get run there? 
Right, sorry, I misinterpreted the ifdefs. We should then merge the android case into the !FreeBsd case like you suggest (although I'm not sure why NetBSD has appeared there now).


https://reviews.llvm.org/D44056