On Tue, Aug 11, 2015 at 10:51 AM, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > On 10 August 2015 at 20:01, John Saxton > <john.saxton@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: >> My organization recently upgraded to C++11 and we're running into a >> problem. We use the POSIX threading library, and in some rare cases >> (pthread_join doesn't exit within a specified timeout, for example), >> we'll kill a thread via pthread_cancel. In C++, thread cancellation is >> implemented via the abi::__forced_unwind exception[1], and in C++03, >> this worked well for us. >> >> In C++11, all destructors are noexcept(true) by default. So if you try >> to cancel a thread that's in a destructor, the abi::__forced_unwind >> exception will escape the destructor, std::terminate() will be >> invoked, and your program dies. I have written a simple program that >> can reproduce this.[2] > > Yes, I've been aware of this problem for some time, and don't have any solution. > >> What's the best way to solve this problem? I could avoid using >> pthread_cancel, but I was hoping to be able to upgrade to C++11 >> without making major changes like that. I could flag all my >> destructors as noexcept(false), but that's tedious and doesn't cover >> third party code like the STL or Boost. I briefly looked into >> std::thread, but it looks like std::thread doesn't have a cancellation >> mechanism. I have reproduced this with a couple of different libstdc++ >> versions (4.8.4-2ubuntu1~14.04 being the newest package I have tested >> with). Would upgrading to a newer version fix my problem? > > No, the problem is inherent to using forced_unwind in C++11. > >> Any other >> ideas? Do I just need to accept the fact that C++11 broke POSIX thread >> cancellation and there's always going to be a chance that >> pthread_cancel will cause my application to terminate? > > Yes, or accept that you shouldn't use pthread_cancel in C++11. I don't > have any better suggestions, sorry. You had a suggestion a few years ago: https://gcc.gnu.org/ml/libstdc++/2012-12/msg00062.html
