Adding an explicit pgmc flag for interaction with GHC by zlonast · Pull Request #11713 · haskell/cabal

zlonast · 2026-04-07T15:36:39Z

IMHO, cc-options (and ld-options and cpp-options and ...) should be always passed when invoking GHC, similarly as ghc-options should be always used when invoking ghc - regardless of what is the intention of a particular GHC-call. GHC might use or not use the options, Cabal cannot know and should not guess.

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zlonast · 2026-04-09T15:49:44Z

I found out why it started working and why it didn't work before.

Since 9.4 it works like this:
https://gitlab.haskell.org/ghc/ghc/-/merge_requests/6949

  , make_ord_flag defFlag "pgmc"
      $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_c   = f }

From 8.8 to 9.2 it worked like this:
https://gitlab.haskell.org/ghc/ghc/-/issues/17919

  , make_ord_flag defFlag "pgmc"
      $ hasArg $ \f -> alterToolSettings $ \s -> s
         { toolSettings_pgm_c   = f
         , -- Don't pass -no-pie with -pgmc
           -- (see #15319)
           toolSettings_ccSupportsNoPie = False
         }

This didn't work before 8.8:
https://gitlab.haskell.org/ghc/ghc/-/issues/17919

sheaf · 2026-04-23T09:12:32Z

I will do my best to take a look at this PR soon.

Copilot

Pull request overview

This PR updates Cabal’s GHC invocation to pass an explicit -pgmc (C compiler program) for GHC ≥ 9.4, with accompanying tests and output normalization to keep the testsuite stable.

Changes:

Add version-gated -pgmc injection to componentGhcOptions (GHC ≥ 9.4).
Update show-build-info golden tests (split expectations across GHC versions) and normalize -pgmc paths in JSON output.
Add a new FFI regression test case that verifies -pgmc wrapper usage.

Reviewed changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
changelog.d/11713.md	Changelog entry describing the `-pgmc`-related behavior change.
cabal-testsuite/src/Test/Cabal/OutputNormalizer.hs	Normalizes `-pgmc` argument paths in `show-build-info` JSON output.
cabal-testsuite/PackageTests/ShowBuildInfo/Custom/custom.test.hs	Formatting-only adjustments to the test script.
cabal-testsuite/PackageTests/ShowBuildInfo/Complex/single.test.hs	Restricts the existing golden test to GHC ≥ 9.4 (where `-pgmc` now appears).
cabal-testsuite/PackageTests/ShowBuildInfo/Complex/single.out	Updates golden output to include normalized `-pgmc` for GHC ≥ 9.4.
cabal-testsuite/PackageTests/ShowBuildInfo/Complex/single-2.test.hs	Adds a new golden test variant for GHC 9.2.x (caret-bounded) without `-pgmc`.
cabal-testsuite/PackageTests/ShowBuildInfo/Complex/single-2.out	New golden output matching the GHC 9.2.x behavior.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/scripts/cc-wrapper.sh	Adds a shell wrapper used to validate `-pgmc` selection in tests.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/foreign-opts-pgmc.cabal	New test package using `ghc-options: -pgmc scripts/cc-wrapper.sh`.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cbits/pgmclib.h	New C header for the FFI test.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cbits/pgmclib.c	New C source asserting the wrapper-injected define is present.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cabal.test.hs	New testsuite driver for the FFI `-pgmc` scenario.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cabal.project	New cabal.project for the test package.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cabal.out	Empty golden output placeholder for the new test.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/README.md	Documents the intent and mechanics of the new FFI test.
cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/Main.hs	New Haskell FFI entrypoint that checks the wrapper-injected value at runtime.
Cabal/src/Distribution/Simple/GHC/Internal.hs	Adds `ghcOptionsSince` helper and sets `ghcOptCcProgram` (i.e. `-pgmc`) for GHC ≥ 9.4.

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mergify · 2026-05-16T18:21:28Z

zlonast · 2026-05-16T20:04:59Z

Windows CI stability is the same as before :(

mergify · 2026-05-16T21:55:43Z

zlonast force-pushed the zlonast/pgmc-option branch from d777763 to ea2ac23 Compare April 7, 2026 15:45

This was referenced Apr 7, 2026

Pass *-options to GHC when compiling ordinary Haskell sources #10969

Open

Add gcc path #11187

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zlonast force-pushed the zlonast/pgmc-option branch 6 times, most recently from f101073 to 7e400d4 Compare April 8, 2026 07:07

zlonast changed the title ~~GHC 9.2.x: Linking error when using -pgmc (PIE/relocation failure)~~ Adding an explicit pgmc flag for interaction with GHC Apr 8, 2026

zlonast force-pushed the zlonast/pgmc-option branch 2 times, most recently from fbec784 to 250c39d Compare April 9, 2026 15:43

zlonast force-pushed the zlonast/pgmc-option branch 2 times, most recently from e929e22 to 4d55bb2 Compare April 10, 2026 13:55

Mikolaj requested a review from sheaf April 23, 2026 09:12

sheaf approved these changes Apr 24, 2026

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Comment thread cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cabal.out Outdated

Comment thread Cabal/src/Distribution/Simple/GHC/Internal.hs Outdated

Comment thread cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cabal.test.hs

zlonast force-pushed the zlonast/pgmc-option branch from 4d55bb2 to 7e0b5ad Compare April 24, 2026 10:01

zlonast added the attention: needs-review label Apr 24, 2026

ulysses4ever requested a review from Copilot April 26, 2026 19:33

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Comment thread cabal-testsuite/PackageTests/FFI/ForeignOptsPgmc/cabal.test.hs Outdated

zlonast force-pushed the zlonast/pgmc-option branch from 7e0b5ad to 598702c Compare April 26, 2026 20:48

This was referenced May 9, 2026

Adding an explicit pgmcxx flag for interaction with GHC #11763

Open

GHC as a Stateless Black Box #11822

Open

ulysses4ever approved these changes May 14, 2026

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Mikolaj removed the attention: needs-review label May 14, 2026

zlonast added the merge me Tell Mergify Bot to merge label May 14, 2026

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Merge of #11713

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mergify Bot mentioned this pull request May 16, 2026

merge queue: embarking master (c44e95a), #11807 and #11713 together #11840

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Adding an explicit pgmc flag for interaction with GHC

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zlonast force-pushed the zlonast/pgmc-option branch from 598702c to b772900 Compare May 16, 2026 20:05

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Merge of #11713

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merge queue: embarking master (52bd676), #11711 and #11713 together #11843

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Merge of #11713

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mergify Bot merged commit aef4733 into haskell:master May 16, 2026
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Adding an explicit pgmc flag for interaction with GHC#11713

Adding an explicit pgmc flag for interaction with GHC#11713
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