{
  "$type": "site.standard.document",
  "bskyPostRef": {
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    "uri": "at://did:plc:pi6woz4d47bkuws673w2il2r/app.bsky.feed.post/3mpah57v4tiv2"
  },
  "path": "/t/ghc-9-12-5-rc2-is-now-available/14313#post_10",
  "publishedAt": "2026-06-26T13:05:25.000Z",
  "site": "https://discourse.haskell.org",
  "tags": [
    "@wz1000",
    "Making sure you're not a bot!"
  ],
  "textContent": "I have modified Stack (in its `fix6934` branch) to depend on `semaphore-compat-2.0.0` and build with GHC 9.12.5-rc2/`Cabal-3.14.2.0`. That works fine on Windows 11 and Linux (Ubuntu via WSL2) but on macOS 26.5.1 (on AArch64) I am getting a failure when I build `stack` with `build --semaphore`.\n\nThe error report is (reformatted, for ease of reading):\n\n\n    ...\n    [217 of 217] Compiling Stack\n    CallStack (from HasCallStack):\n      fdReadByte, called at libraries/semaphore-compat/src/System/Semaphore/Internal/Posix.hs:159:9 in semaphore-compat-2.0.0-068d:System.Semaphore.Internal.Posix\n      waitOnSemaphore, called at compiler/GHC/Driver/MakeSem.hs:321:51 in ghc-9.12.4.20260614-868c:GHC.Driver.MakeSem: end of file (fd=13)\n\n    Error: [S-7282]\n           Stack failed to execute the build plan.\n\n           While executing the build plan, Stack encountered the error:\n\n           [S-7011]\n           While building package stack-3.12.0 (scroll up to its section to see the error) using:\n           .../ghc-9.12.4.20260614/setup/setup\n             --verbose=1\n             --builddir=.../ghc-9.12.4.20260614\n             build lib:stack exe:stack\n             --semaphore v2-stack_1sPonmdUx\n             --ghc-options \" -fdiagnostics-color=always\"\n\n\nThere is no macOS-specific code involved at Stack’s end, so my hypothesis is that there may be something up with `semaphore-combat-2.0.0` (perhaps in combination with `Cabal-3.14.2.0`) on macOS.\n\nI turned on Stack’s and Cabal’s verbose reporting, and it ends with:\n\n\n    2026-06-26 14:09:22.878725: [info] [217 of 217] Compiling Stack\n    2026-06-26 14:09:23.030317: [warn] fdWriteByte(fd=13): resource vanished (Broken pipe)\n    2026-06-26 14:09:23.118799: [debug] Loading project config file stack-ghc-9.12.5.yaml\n    2026-06-26 14:09:23.120822: [debug] Use of Casa server enabled: (CasaRepoPrefix \"https://casa.stackage.org\", 1280).\n    2026-06-26 14:09:23.122446: [debug] (SQL) SELECT COUNT(*) FROM \"last_performed\" WHERE (\"action\"=?) AND (\"timestamp\">=?); [PersistInt64 1,PersistUTCTime 2026-06-25 13:09:23.122421 UTC]\n    2026-06-26 14:09:23.122775: [error]\n    ...\n\n\nThe `[info]` and `[warn]` lines are Cabal’s reporting. The `[debug]` lines reflect Stack’s usual verbose reporting.\n\nEDIT: There was a bug and (thanks to @wz1000) there is a fix:\n\n  * Making sure you're not a bot!\n\n",
  "title": "GHC 9.12.5-rc2 is now available"
}