{
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  "path": "/t/ghc-9-12-5-rc2-is-now-available/14313#post_1",
  "publishedAt": "2026-06-24T09:33:59.000Z",
  "site": "https://discourse.haskell.org",
  "tags": [
    "downloads.haskell.org",
    "GHCup",
    "25087",
    "27253",
    "25926",
    "27124",
    "27261",
    "27106",
    "26416",
    "27121",
    "26929",
    "26642",
    "26693",
    "Juspay",
    "QBayLogic",
    "Channable",
    "Haskell Foundation",
    "Serokell",
    "Well-Typed",
    "Tweag",
    "Dotcom-Monitor",
    "LoadView",
    "Web Hosting Buddy",
    "Find My Electric",
    "Standard Chartered",
    "UpCloud",
    "Mercury"
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  "textContent": "The GHC developers are very pleased to announce the availability\nof the second release candidate for GHC 9.12.5, ghc-9.12.5-rc2. The first release candidate did not receive an announcement since promptly after publishing it, an urgent issue with distribution of the process library on macos was discovered. This is now fixed.\nBinary distributions, source distributions, and documentation are available at\ndownloads.haskell.org and via GHCup.\n\nGHC 9.12.5 is a bug-fix release fixing many issues of a variety of\nseverities and scopes, including:\n\n  * Implement version 2 of the ghc `semaphore` protocol for GHC’s `-jsem` jobserver on Linux and other `POSIX` platforms (#25087, #27253)\n  * several improvements to the pattern match checker (#25926, #27124)\n  * several improvements to the demand analyser (#27261, #27106, #26416)\n  * several fixes regarding the interaction of ticks and coercions (#27121, #26929, #26642, #26693)\n  * several fixes for blackholes (#27261)\n\n\n\n… and many more\n\nMind that the very important overhaul of the semaphore-compat library to v2 is included in this release and that the semaphore feature will only start working with cabal-install 3.18 again, which is sadly a breaking but necessary change.\n\nA full accounting of these fixes can be found in the\nrelease notes. As always, GHC’s release status, including planned future\nreleases, can be found on the GHC Wiki status.\n\nThis release candidate will have a two-week testing period. If all goes well\nthe final release will be available the week of 8 July 2026.\n\nGHC development is sponsored by:\n\n  * Juspay\n  * QBayLogic\n  * Channable\n  * Haskell Foundation\n  * Serokell\n  * Well-Typed\n  * Tweag\n  * Dotcom-Monitor\n  * LoadView\n  * Web Hosting Buddy\n  * Find My Electric\n  * Standard Chartered\n  * UpCloud\n  * Mercury\n\n\n\nWe would like to thank these sponsors and other anonymous contributors\nwhose on-going financial and in-kind support has facilitated GHC maintenance\nand release management over the years. Finally, this release would not have\nbeen possible without the hundreds of open-source contributors whose work\ncomprise this release.\n\nAs always, do give this release a try and open a ticket if you see\nanything amiss.",
  "title": "GHC 9.12.5-rc2 is now available"
}