Changes to support new GHC 9.4's new Windows toolchain #8071

bgamari · 2022-03-30T17:45:06Z

As noted in GHC #21068, the lld linker used on Windows by GHC 9.4 and later does not support object merging. Consequently, --enable-library-for-ghci can no longer be supported on this platform. In this MR we:

turn --enable-library-for-ghci into an error on platforms where it is not supported.
teach Cabal to use llvm-ar's L modifier when available, which is now necessary when building static archives on Windows (since the archive may contain other archives, as noted in GHC #21068)

Please include the following checklist in your PR:

Patches conform to the coding conventions.
Any changes that could be relevant to users have been recorded in the changelog.
The documentation has been updated, if necessary.

Please also shortly describe how you tested your change. Bonus points for added tests!

bgamari · 2022-03-30T17:45:39Z

This supercedes #8062.

phadej · 2022-03-30T17:47:56Z

Cabal/src/Distribution/Simple/Program/Ar.hs

  -- Our solution is to use "ar r" in the simple case when one call is enough.
  -- When we need to call ar multiple times we use "ar q" and for the last
  -- call on OSX we use "ar qs" so that it'll make the index.

  let simpleArgs  = case hostOS of
             OSX -> ["-r", "-s"]
+             _ | dashLSupported -> ["-qL"]


is this (and will be) harmless on linux?

Indeed. I have seen no traditional use of .a archives which would want the non--L behavior; you always want the merging behavior that -L introduces. It's somewhat incredible that binutils' ar does not support it yet.

phadej · 2022-03-30T17:49:26Z

General note: This issue looks like some kind of release candidate of cabal-install will be required for GHC alphas/betas/release-candidates, as it seems it won't be possible to use old cabal-install with GHC-9.4 on windows?

Is this right, @bgamari?

bgamari · 2022-04-01T14:53:01Z

General note: This issue looks like some kind of release candidate of cabal-install will be required for GHC alphas/betas/release-candidates, as it seems it won't be possible to use old cabal-install with GHC-9.4 on windows?

Is this right, @bgamari?

Yes, sadly this is the case.

Mikolaj

LGTM. Thank you.

jneira

lgtm, thanks!
should not we backport this to 3.6?

As noted in GHC #21068, the lld linker used on Windows by GHC 9.4 and later does not support object merging. Consequently, --enable-library-for-ghci can no longer be supported on this platform.

As of 9.4, GHC on Windows may produce .o files that are in fact archive files due to the lack of object merging support in the lld linker (see GHC #21068). Consequently, we must ensure that `ar` merges input archives' members, not add them as a single entry.

jneira · 2022-04-07T10:42:31Z

should not we backport this to 3.6?

i guess make 3.6 work with ghc-9.4 needs more changes and they were not already backported?

Mikolaj · 2022-04-07T17:10:53Z

@bgamari: please let us know if you think we need to backport this. Until then, let's leave it be, I guess?

bgamari · 2022-04-08T03:40:53Z

Given that users are advised to use the most recent cabal-install release with new GHC releases, I don't believe that backporting is necessary.

Mikolaj · 2022-04-08T11:13:23Z

That implies we'd need to release cabal 3.8 before GHC 9.4. We'll see...

Bodigrim · 2022-05-04T00:25:29Z

Any plans for cabal RC soon? Otherwise testing of GHC 9.4-alpha1 on Windows is blocked.

Mikolaj · 2022-05-04T11:12:22Z

I think the idea was to test a nightly build [edit: of master branch]. Do I remember correctly, @gbaz, @emilypi? Where are our nightly builds? Gitlab somewhere?

jneira · 2022-05-04T20:34:52Z

validate workflow generate artifacts, to do the dogfooding but they also can be downloaded, i guess we could use them: https://github.com/haskell/cabal/actions/runs/2270699540#artifacts

Mikolaj · 2022-06-01T09:22:41Z

RC seems to be ready (famous last words): https://downloads.haskell.org/~cabal/cabal-install-3.8.1.0-rc1/

Please kindly test and give feedback.

@Bodigrim, @bgamari

andreabedini · 2022-06-01T09:55:01Z

For ghcup users:

ghcup install cabal --url https://downloads.haskell.org/~cabal/cabal-install-3.8.1.0-rc1/cabal-install-3.8.0.20220526-x86_64-linux-deb10.tar.xz 3.8.0.20220526

Mikolaj · 2022-06-01T10:19:12Z

@andreabedini: the "3.8.0.2022052" in your commandline seems cut off; no idea if that matters...

andreabedini · 2022-06-01T10:34:24Z

@Mikolaj that would be just a release tag for ghcup. Fixed it anyway! Thanks.

Bodigrim · 2022-06-01T21:04:15Z

@Mikolaj I checked cabal HEAD once this was merged, it worked fine with GHC 9.4 on Windows. I’m AFK, so cannot check the RC before next week.

Mikolaj · 2022-06-01T21:09:33Z

Thank you for the confirmation. 3.8 is very close to master's HEAD and we probably haven't broken Windows GHC 9.4 support since then, so I hope we are fine.

Mikolaj · 2022-06-02T12:42:03Z

The official tags have dropped; we are now committed: https://github.com/haskell/cabal/tree/cabal-install-v3.8.1.0-rc1.

hasufell · 2024-01-03T16:14:44Z

Given that users are advised to use the most recent cabal-install release with new GHC releases, I don't believe that backporting is necessary.

This doesn't match ghcup's policy. I'm in the process of backporting this change to 3.6.

This is the only issue I've heard about cabal-3.6 and ghc-9.4 compatibility. Are any others known?

phadej · 2024-01-03T17:33:25Z

Are any others known?

Cabal-3.6 does not support GHC-9.6. Period.

It works because of happy accident (well, actually it doesn't on windows!)

If proper support to be added, then all other changes related to GHC version have to be added. (see for bare minimum https://github.com/haskell/cabal/wiki/Making-a-release#for-release-for-new-ghc-version)

In fact, GHC-3.10.2.0 support of GHC-9.8 is partial, which is unfortunate.

hasufell · 2024-01-03T17:42:37Z

Cabal-3.6 does not support GHC-9.6. Period.

That is not an issue. I'm only interested in Cabal-3.6 + GHC-9.4.

If proper support to be added, then all other changes related to GHC version have to be added. (see for bare minimum https://github.com/haskell/cabal/wiki/Making-a-release#for-release-for-new-ghc-version)

Thanks for the pointer.

phadej · 2024-01-03T17:44:56Z

That is not an issue. I'm only interested in Cabal-3.6 + GHC-9.4.

Sorry, I got versions wrong. Cabal-3.6 doesn't support GHC-9.4. (GHC-9.4 bundles Cabal-3.8).

hasufell · 2024-01-03T17:48:40Z

That is not an issue. I'm only interested in Cabal-3.6 + GHC-9.4.

Sorry, I got versions wrong. Cabal-3.6 doesn't support GHC-9.4. (GHC-9.4 bundles Cabal-3.8).

Sure, I'm just trying to contain damage from too eagerly recommending GHC 9.4, which is mostly busted on windows due to the radical toolchain changes.

ulysses4ever · 2024-01-04T00:40:23Z

@phadej

In fact, GHC-3.10.2.0 support of GHC-9.8 is partial

What do you mean by partial exactly? The forgotten extension?

Related: * haskell/ghcup-hs#966 We bump this, although 'cabal run' is known to be broken on windows: haskell/cabal#9334 However, backporting more patches to 3.6 is not sustainable. Initially, I tried to backport haskell/cabal#8071, but it's not clear whether that is the only thing that causes compatibility issues with GHC 9.4 and might drive us into an awkward situation as well.

phadej · 2024-01-04T11:48:44Z

The forgotten extension?

Not forgotten, but left out because unwillingness to make a major version bump release

Also I don't trust normaliseGhcArgs to do the most accurate job in presence of GHC-9.8's new warning stuff (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-warning-pragmas-with-categories.rst). I think normaliseGhcArgs is conservative, so using new (especially warning group) flags will always cause recompilation, but maybe not.

EDIT: also https://downloads.haskell.org/ghc/latest/docs/users_guide/using-warnings.html#ghc-flag--Wcompat group has changed previously but not in 9.8 AFAIK, but as issue above, it's a minor inconsistency. It's unluckily to be hit by that.

andreabedini · 2024-01-17T06:01:06Z

Just drive by comment to notice that @hasufell is most likely interested in cabal-install (which is what GHCup distributes) and not Cabal. cabal-install can use a newer version of Cabal if needed.

phadej reviewed Mar 30, 2022

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bgamari force-pushed the wip/disable-ghci-libs-on-windows branch from a41edc4 to 4b372fc Compare April 6, 2022 19:10

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Mikolaj added merge me Tell Mergify Bot to merge and removed attention: needs-review labels Apr 6, 2022

bgamari and others added 4 commits April 6, 2022 21:31

Cabal: Disable GHCi libraries on Windows with GHC >=9.4

fa7b564

As noted in GHC #21068, the lld linker used on Windows by GHC 9.4 and later does not support object merging. Consequently, --enable-library-for-ghci can no longer be supported on this platform.

Use ar -L when available

681a151

As of 9.4, GHC on Windows may produce .o files that are in fact archive files due to the lack of object merging support in the lld linker (see GHC #21068). Consequently, we must ensure that `ar` merges input archives' members, not add them as a single entry.

Add changelog entry for GHC 9.4 Windows changes

020a7f8

Disable GHCi libraries by default on Windows

cabd857

andreabedini force-pushed the wip/disable-ghci-libs-on-windows branch from 9eda67c to cabd857 Compare April 6, 2022 21:31

mergify bot merged commit 1304347 into haskell:master Apr 6, 2022

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Fix build with Cabal 3.4 wxHaskell/wxHaskell#40

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GHCup selected combination of cabal / GHC versions does not work on windows haskell/ghcup-hs#966

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Wip/cabal install v3.6.2.0 p2 hasufell/cabal#2

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Changes to support new GHC 9.4's new Windows toolchain #8071

Changes to support new GHC 9.4's new Windows toolchain #8071

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