Pass *-options to GHC when compiling ordinary Haskell sources by zlonast · Pull Request #10969 · haskell/cabal

zlonast · 2025-05-22T16:23:54Z

Will close issues #9801 #4435
Main idea #9801 (comment)

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.

cc-options, cxx-options, jspp-options, asm-options, cmm-options, ld-options, cpp-options,
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.

cc-options and cxx-options still need to be separated (C/C++) for versions below 8.10.
https://gitlab.haskell.org/ghc/ghc/-/issues/16477

Template Α: This PR modifies behaviour or interface

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The documentation has been updated, if necessary.
Manual QA notes have been included.
Tests have been added. (Ask for help if you don’t know how to write them! Ask for an exemption if tests are too complex for too little coverage!)

Depends-on: #11711
Depends-on: #11713

zlonast · 2025-05-22T17:54:50Z

I probably need to think about tests, maybe something started working besides CApiFFI 🤔

zlonast · 2025-05-22T18:12:29Z

~~Ok, this only works for things newer than 8.8~~
~~gcc: fatal error: cannot specify ‘-o’ with ‘-c’, ‘-S’ or ‘-E’ with multiple files~~

Ok, got it, we just need to separate the flags -optc and -optcxx
Pass -optcxx for GHC >= 8.10 #7072

zlonast · 2025-05-24T17:04:23Z

@ulysses4ever @phadej It's not very easy to add flags to sources files due to backward compatibility, so for now I suggest considering the pull request as is ¯\_(ツ)_/¯ (Anyway, this solved the problem with macros in header files)

ulysses4ever

Great start, thank you! Below are some inline questions.

One general question: did you check that this doesn't lead to duplicated options when cabal calls GHC? I assume other *-options are passed today sometimes. So, sometimes we'll get those options passed as today and through your change too. Is that right? It seems undesirable.

It's not very easy to add flags to sources files due to backward compatibility

Can you be more specific? Do you mean it's hard to test on older GHCs? This shouldn't be a problem because the tests can run for specific versions of GHC (e.g. starting from 8.10).

geekosaur

Same concerns as @ulysses4ever raised.

phadej · 2025-05-24T19:39:44Z

did you check that this doesn't lead to duplicated options when cabal calls GHC?

Yes, it looks like so.

I'd say the problem is rather that GhcOptions is not used uniformly. There is e.g. componentCcGhcOptions which does set ghcOptCcOptions. Why these don't show up when compiling files CApiFFI headers?

IMHO, it's wrong that there are separate componentAsmGhcOptions, componentJsGhcOptions, componentGhcOptions. There should be just one componentGhcOptions with all the options, and then it's up to GHC which ones are relevant, and which aren't.

EDIT: There might be situations where ghcOptMode or something like that is different, and input files "obviously". But the bulk of options should be the same. Starting with verbosity. I'd imagine there is only single line in the codebase which does ghcOptVerbosity = toFlag (min verbosity normal). Currently there are six copies of that. Cannot be right. I suspect there are many subtle inconsistencies hiding because of that.

EDIT: So AFAICT, this is not the correct fix, not what I'd imagine seeing.

Mikolaj · 2026-03-26T18:57:42Z

Sadly, @mpickering may not be able to contribute to this PR any more. @zlonast: how can we help to get it through?

zlonast · 2026-03-26T19:53:29Z

@Mikolaj Hi! As the author, I think it works and we can be merge it 😄

But perhaps you want to pay attention to this:

The GCC issue: We want to explicitly pass the GCC path, but for versions < 9.4, it causes linking failures for reasons I haven't been able to isolate yet.
Lack of tests: I haven't implemented tests for the new flag options yet.

ulysses4ever · 2026-03-27T17:23:05Z

@zlonast thank you for your work here and for the summary in partiular. Quetsions:

The GCC issue: We want to explicitly pass the GCC path, but for versions < 9.4, it causes linking failures for reasons I haven't been able to isolate yet.

This looks rather serious. Can you elaborate with example scenarios? E.g. will I not be able to build any package with c-sources after this change if I need to use 9.4?

FTR, we are supposed to maintain ccompatibility with any GHC released last 5 years. GHC 9.4.8 was released 10 November 2023, so there's still 2.5 years of it staying in this support window.

Lack of tests: I haven't implemented tests for the new flag options yet.

Do you think you could add some?

zlonast · 2026-04-07T15:48:34Z

This must happen before this pull request is merged.

The GCC issue: We want to explicitly pass the GCC path, but for versions < 9.4, it causes linking failures for reasons I haven't been able to isolate yet.

issue #11712

pr fix #11713

Lack of tests: I haven't implemented tests for the new flag options yet.

tests #11711

zlonast · 2026-04-08T10:29:23Z

-optc-O2,-optcxx-O2,-opta-O2 into a separate pull request #11716

zlonast · 2026-04-08T14:34:16Z

I found the problem and left a link in this #10969 (comment).

I've only left two things in that pr.

the solution itself
code refactoring [significance: significant]

I suggest checking the compilation of the entire clc-stackage again before merging.

mergify · 2026-05-14T09:57:08Z

Deprecation notice: This pull request comes from a fork and was rebased using bot_account impersonation. This capability will be removed on July 1, 2026. After this date, the rebase action will no longer be able to rebase fork pull requests with this configuration. Please switch to the update action/command to ensure compatibility going forward.

mergify · 2026-05-14T09:57:08Z

rebase

✅ Branch has been successfully rebased

Refactor componentGhcOptions for pass *-options to all invoking GHC. During the refactoring process we needed to add componentGhcOptions to all Haskell sources. It was also worth add linkGhcOptions to linkLibrary same as componentGhcOptions to linkExecutable, linkFLib. Add test for PackageTests/FFI/ForeignOptsCapi to pass cc-options flags to *.h. Fixes haskell#9801 haskell#4435 Co-authored-by: Mikolaj Konarski <mikolaj.konarski@gmail.com>

Co-authored-by: Yuriy Syrovetskiy <git-orbi@cblp.su>

zlonast · 2026-05-17T10:37:02Z

To summarize the current state of this PR:

All previous discussions have been resolved.
All prerequisite PRs have been merged.
Tests are written and passing.

Regarding the tests, the two added test cases directly address what was requested in the linked issues (#9801, #4435):

The first test ForeignOptsCapi demonstrates that the flags now successfully reach the linking objects.
The second test ForeignSourceTemplateHaskell shows the flexibility of our approach: everything works as expected even within TemplateHaskell.

@Mikolaj @ulysses4ever I believe this is now ready.

Before GHC 8.10, Cabal passed both `cc-options` and `cxx-options` via a single GHC flag, `-optc`. When GHC 8.10 introduced `-optcxx`, Cabal picked up this change: `cc-options` and `cxx-options` are now mapped to `-optc` and `-optcxx`, respectively. However, Cabal also changed its behavior for older GHC versions (8.8 and below): it now sends `cc-options` and `cxx-options` through separate instances of `-optc`. Co-authored-by: Artem Pelenitsyn <a.pelenitsyn@gmail.com>

Mikolaj · 2026-05-21T10:29:47Z

This looks great! Are the conversations resolved but not marked, or not yet resolved?

zlonast · 2026-05-21T10:35:48Z

@ulysses4ever For now, I'll put the merge me label, but if you want me to change the comments, feel free to write about it

mergify · 2026-05-23T16:51:51Z

Merge Queue Status

✅ Entered queue — 2026-05-23 16:51 UTC · Rule: default
✅ Checks started — 2026-05-23 17:32 UTC · on draft merge queue: embarking master (6989d21) and [#11862 + #10969] together #11868
❌ Checks failed
✂️ Bisecting to identify the failing PR (round 1/1)
✅ Checks passed · on draft merge queue: embarking master (6989d21) and [#10969 + #11857 + #11856] together #11871
✅ Merged — 2026-05-23 21:59 UTC · at 1da4f9eec259a76acf2fafc9a2dca79723014578 · merge

This pull request spent 5 hours 7 minutes 18 seconds in the queue, including 3 hours 5 minutes 2 seconds running CI.

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zlonast force-pushed the options-invoking-ghc branch 2 times, most recently from 1bd501e to c3e68be Compare May 22, 2025 17:02

zlonast marked this pull request as ready for review May 22, 2025 17:52

zlonast added this to the Considered for 3.16 milestone May 22, 2025

zlonast force-pushed the options-invoking-ghc branch 10 times, most recently from a439429 to 1b8e5bb Compare May 24, 2025 15:33

zlonast requested review from mpickering, phadej and ulysses4ever May 24, 2025 17:05

ulysses4ever reviewed May 24, 2025

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Comment thread changelog.d/pr-10969.md

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Comment thread cabal-testsuite/PackageTests/FFI/ForeignOptsCapi/README.md

ulysses4ever added the attention: needs-review label May 24, 2025

This was linked to issues May 24, 2025

cc-options do not get passed to GHC #4435

Closed

Cabal doesn't pass cc-options to GHC when compiling ordinary Haskell sources #9801

Closed

geekosaur requested changes May 24, 2025

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phadej reviewed May 24, 2025

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zlonast force-pushed the options-invoking-ghc branch 3 times, most recently from 0b74992 to 37417aa Compare May 28, 2025 16:26

zlonast force-pushed the options-invoking-ghc branch from a8f1b13 to 6b7957c Compare March 27, 2026 10:48

zlonast force-pushed the options-invoking-ghc branch from 6b7957c to e522b12 Compare April 7, 2026 14:53

zlonast force-pushed the options-invoking-ghc branch from e522b12 to afa91a2 Compare April 8, 2026 10:27

zlonast force-pushed the options-invoking-ghc branch from afa91a2 to 858d618 Compare April 8, 2026 10:43

zlonast changed the title ~~Pass *-options and -pgmc gcc to GHC when compiling ordinary Haskell sources~~ Pass *-options to GHC when compiling ordinary Haskell sources Apr 8, 2026

zlonast force-pushed the options-invoking-ghc branch from 858d618 to 7de85b7 Compare April 8, 2026 12:27

zlonast mentioned this pull request May 13, 2026

GHC as a Stateless Black Box #11822

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4 tasks

zlonast and others added 2 commits May 17, 2026 12:54

add test for foreign source in TemplateHaskell

db14107

Co-authored-by: Yuriy Syrovetskiy <git-orbi@cblp.su>

ulysses4ever approved these changes May 17, 2026

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Comment thread Cabal/src/Distribution/Simple/GHCJS.hs Outdated

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