GHC team update 38 (#99)

* GHC team update 38

* Update 2024-11-28-ghc-update-38.md

* Update 2024-11-28-ghc-update-38.md

* Update 2024-11-28-ghc-update-38.md

* Update 2024-11-28-ghc-update-38.md

* Update 2024-11-28-ghc-update-38.md

* Update 2024-11-28-ghc-update-38.md

* Update 2024-11-28-ghc-update-38.md

* Update 2024-11-28-ghc-update-38.md

---------

Co-authored-by: Luite Stegeman <[email protected]>

Author: hsyl20

blog/2024-11-28-ghc-update-38.md

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+---
+slug: 2024-11-28-ghc-update
+title: "IOG GHC Update #38"
+authors: [sylvain,doyougnu,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).
+
+## High-level Summary
+
+The team has been working on the preparation of a GHC 9.6.7 release with a fix for the Cardano node and
+investigating how to simplify the build of GHC distributions.
+
+See details below for the more general maintenance and improvement fixes.
+
+## Details
+
+### Performance
+
+Luite: Created a stand-alone testcase for [GHC#25284](https://gitlab.haskell.org/ghc/ghc/-/issues/25284) so possible mitigations can be tested quickly. Discussed some options to improve the flags we created earlier ([GHC!13556](https://gitlab.haskell.org/ghc/ghc/-/merge_requests/13556)).
+
+Jeff: investigated variations in Plutus criterion benchmarks (possibly related to GC).
+
+### Toolchain
+
+Luite: Worked on preparing the upcoming GHC 9.6.7 release by backporting and testing patches: See [luite/ghc/wip/ghc-9.6-backports](https://gitlab.haskell.org/luite/ghc/-/commits/wip/ghc-9.6-backports).
+
+Sylvain: investigated how to build GHC differently (e.g. without Hadrian). Work still in progress.
+
+Sylvain: experimented with using HPP instead of the C toolchain as a CPP preprocessor to build GHC. I had to implement some features and to fix a few bugs to support CPP as used in the RTS:
+- Add support for macros with empty argument list: [HPP#7](https://github.com/acowley/hpp/pull/7)
+- Fix removal of C comments (otherwise we tried to substitute macros in them): [HPP#8](https://github.com/acowley/hpp/pull/8)
+- Add support for variadic macros: [HPP#10](https://github.com/acowley/hpp/pull/10)
+- Fix line counting for `__LINE__` support and `#line` token insertion: [HPP#6](https://github.com/acowley/hpp/pull/6), [HPP#11](https://github.com/acowley/hpp/pull/11) and [HPP#12](https://github.com/acowley/hpp/pull/12)
+
+Shoutout to HPP's author and maintainer Anthony Cowley who has been very responsive.
+
+### Maintenance
+
+Sylvain: reviewed GHC patches about the JS backend