Bug when using TimerManager/GHC.Event ?
It was suggested on #haskell that this is a bug and that I should report it here. Hopefully this is the simplest possible example that shows the issue. The code sample I got from a StackOverflow answer (https://stackoverflow.com/a/25488677) which I found just trying to learn how to use GHC.Event properly so presumably, and it seemed to work there, so I assume it is still valid code (but let me know if not!).
Minimal example repo is here: https://github.com/ddellacosta/timermanager-bug, please see Main.hs
I'm on on OS X 10.13.6, and hopefully the shell dump below combined with the repo above gives you everything else you need:
$ cabal new-configure Resolving dependencies... Build profile: -w ghc-8.4.3 -O1 In order, the following would be built (use -v for more details): - timermanager-bug-0.1.0.0 (exe:timermanager-bug) (first run) $ cabal new-build Build profile: -w ghc-8.4.3 -O1 In order, the following will be built (use -v for more details): - timermanager-bug-0.1.0.0 (exe:timermanager-bug) (first run) Configuring executable 'timermanager-bug' for timermanager-bug-0.1.0.0.. clang: warning: argument unused during compilation: '-nopie' [-Wunused-command-line-argument] Preprocessing executable 'timermanager-bug' for timermanager-bug-0.1.0.0.. Building executable 'timermanager-bug' for timermanager-bug-0.1.0.0.. [1 of 1] Compiling Main ( Main.hs, /Users/ddellacosta/code/timermanager-bug/dist-newstyle/build/x86_64-osx/ghc-8.4.3/timermanager-bug-0.1.0.0/x/timermanager-bug/build/timermanager-bug/timermanager-bug-tmp/Main.o ) Linking /Users/ddellacosta/code/timermanager-bug/dist-newstyle/build/x86_64-osx/ghc-8.4.3/timermanager-bug-0.1.0.0/x/timermanager-bug/build/timermanager-bug/timermanager-bug ... clang: warning: argument unused during compilation: '-nopie' [-Wunused-command-line-argument] clang: warning: argument unused during compilation: '-nopie' [-Wunused-command-line-argument] $ cabal new-exec timermanager-bug timermanager-bug: user error (Pattern match failure in do expression at libraries/base/GHC/Event/Thread.hs:216:3-10) $
Let me know if there's any more information I can supply! Apologies if this is not actually a bug but something I'm doing wrong! Thanks!