diff --git a/Cabal/src/Distribution/Compat/Process.hs b/Cabal/src/Distribution/Compat/Process.hs index 7d02ba9fe59..b7c8be87280 100644 --- a/Cabal/src/Distribution/Compat/Process.hs +++ b/Cabal/src/Distribution/Compat/Process.hs @@ -18,23 +18,44 @@ import qualified System.Process as Process import System.Process (waitForProcess) #endif +#if defined(mingw32_HOST_OS) && MIN_VERSION_process(1,6,9) +import System.IO.Unsafe (unsafePerformIO) +import System.Win32.Info.Version (dwMajorVersion, dwMinorVersion, getVersionEx) +#endif + ------------------------------------------------------------------------------- -- enableProcessJobs ------------------------------------------------------------------------------- +#if defined(mingw32_HOST_OS) && MIN_VERSION_process(1,6,9) +-- This exception, needed to support Windows 7, could be removed when +-- the lowest GHC version cabal supports is a GHC that doesn’t support +-- Windows 7 any more. +{-# NOINLINE isWindows8OrLater #-} +isWindows8OrLater :: Bool +isWindows8OrLater = unsafePerformIO $ do + v <- getVersionEx + pure $ (dwMajorVersion v, dwMinorVersion v) >= (6, 2) +#endif + -- | Enable process jobs to ensure accurate determination of process completion -- in the presence of @exec(3)@ on Windows. -- -- Unfortunately the process job support is badly broken in @process@ releases -- prior to 1.6.9, so we disable it in these versions, despite the fact that --- this means we may see sporatic build failures without jobs. +-- this means we may see sporadic build failures without jobs. +-- +-- On Windows 7 or before the jobs are disabled due to the fact that +-- processes on these systems can only have one job. This prevents +-- spawned process from assigning jobs to its own children. Suppose +-- processs A spawns process B. The B process has a job assigned (call +-- it J1) and when it tries to spawn a new process C the C +-- automatically inherits the job. But at it also tries to assign a +-- new job J2 to C since it doesn’t have access J1. This fails on +-- Windows 7 or before. enableProcessJobs :: CreateProcess -> CreateProcess -#ifdef MIN_VERSION_process -#if MIN_VERSION_process(1,6,9) -enableProcessJobs cp = cp {Process.use_process_jobs = True} -#else -enableProcessJobs cp = cp -#endif +#if defined(mingw32_HOST_OS) && MIN_VERSION_process(1,6,9) +enableProcessJobs cp = cp {Process.use_process_jobs = isWindows8OrLater} #else enableProcessJobs cp = cp #endif diff --git a/changelog.d/pr-7844 b/changelog.d/pr-7844 new file mode 100644 index 00000000000..c46b59d2cca --- /dev/null +++ b/changelog.d/pr-7844 @@ -0,0 +1,8 @@ +synopsis: Disable job management on Windows 7 +packages: Cabal +prs: #7844 +significance: significant + +description: { +- cabal now works on Windows 7 +}