[GHC 7.10.1-RC2] shake and vector-algorithms test suites hang

[MP2E]

Whenever nix runs ./Setup test for vector-algorithms or shake with GHC 7.10.1-RC2 the tests run forever, I left them running for 6 hours(!) on an i7 3770K. The tests don't give me any failing messages, they just run until I hit ctrl+c

GHC 7.8.4 does not have this issue

vector-algorithms
http://lpaste.net/120194

shake
http://lpaste.net/120195

strace on shake build
http://lpaste.net/120197

I originally asked for help on #ghc but pacak could not reproduce these issues, and he told me to try running shake-test directly instead of running ./Setup test (which runs runhaskell). When I overrode checkPhase to run the local binary directly the test fails immediately because it can't find a file that hasn't been created yet. (Probably created by installPhase?)

Direct run of ./dist/build/shake-test/shake-test
http://lpaste.net/120199

Direct run of the test from vector-algorithms:
http://lpaste.net/120398

Note that disabling the test suite for these 2 packages works fine, and projects that depend on them work as intended

[peti]

I observe the same problem, but I have no idea what's causing it.

[bennofs]

@peti Compiling Setup.hs with -threaded should fix the issue. The problem is that the Cabal library uses the FFI to wait for the test process to finish, and uses a thread to consume the output of the test process (it's passed to a pipe). Without -threaded, the FFI call will block the whole program and the pipe consumers never run, therefore filling up the pipe.

[bennofs]

See haskell/cabal#2398

[peti]

Ah, very nice catch. Thanks for the pointer.

[MP2E]

Thanks for the help, @bennofs !

[nomeata]

BTW, I have submitted a work-around for this at haskell/cabal#2913 that does not require a threaded Setup.