GHC update 47 (#108)

Author: hsyl20

blog/2025-06-12-ghc-update-47.md

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+---
+slug: 2025-06-12-ghc-update
+title: "IOG GHC Update #47"
+authors: [sylvain,luite]
+tags: [ghc,ghc-update]
+---
+
+Triweekly update from the GHC DevX team at IOG.
+
+<!-- truncate -->
+
+Previous updates can be found [here](https://engineering.iog.io/tags/ghc-update).
+
+The team attended
+[HEW](https://haskell.foundation/events/2025-haskell-ecosystem-workshop.html),
+[HIW](https://haskell.foundation/events/2025-haskell-implementors-workshop.html),
+and [Zurihac](https://zfoh.ch/zurihac2025/) in Switzerland.
+
+
+Luite: chaired a session at HIW.
+
+Luite: fixed a Windows cross-compilation issue in haskell.nix.
+[haskell.nix#2361](https://github.com/input-output-hk/haskell.nix/issues/2361)
+[haskell.nix!2385](https://github.com/input-output-hk/haskell.nix/pull/2385).
+
+Sylvain: fixed compilation of C files with GHC when the package database doesn't
+contain the rts (useful when building the RTS).
+[GHC#26018](https://gitlab.haskell.org/ghc/ghc/-/issues/26018) and
+[GHC!14300](https://gitlab.haskell.org/ghc/ghc/-/merge_requests/14300).
+
+Sylvain: removed unsafe `emptyModBreaks`
+[GHC!14348](https://gitlab.haskell.org/ghc/ghc/-/merge_requests/14348).
+
+Sylvain: debugged STM performance issue and provided a fix (not merged yet).
+[GHC#26028](https://gitlab.haskell.org/ghc/ghc/-/issues/26028)
+[GHC!14354](https://gitlab.haskell.org/ghc/ghc/-/merge_requests/14354).