cling, xeus-cling: vendor llvm #283989

wegank · 2024-01-26T12:00:03Z

Description of changes

This PR attempts to build Cling with root's LLVM fork, as the packages involved are the last blockers for the removal of LLVM 8-11 in Nixpkgs (see #283954). The refactor basically follows https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=cling.

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lorenz · 2024-01-26T14:13:29Z

FYI there seems to be a small patchset which allows using LLVM 17 with xeus-cling: jupyter-xeus/xeus-cling@main...lackhole:xeus-cling:llvm-16

wegank · 2024-01-26T14:41:48Z

FYI there seems to be a small patchset which allows using LLVM 17 with xeus-cling: jupyter-xeus/xeus-cling@main...lackhole:xeus-cling:llvm-16

I guess this won't work unless Cling is based on LLVM 16...

wegank · 2024-01-27T01:45:20Z

Result of nixpkgs-review pr 283989 run on aarch64-darwin 1

2 packages built:

cling
xeus-cling

thomasjm · 2024-01-27T02:57:20Z

A few thoughts here, it's been a few years so I don't remember everything perfectly:

Cling is pretty tightly bound to a given LLVM release, in this case LLVM 9. I don't think you're going to have luck trying to build Cling with a totally different LLVM version.
Building with Root's LLVM fork could potentially work, but why? You'll just have replaced the current Nixpkgs build of LLVM 9 with another (slightly weird/patched) version.
Over its history, Cling has sometimes required patches to both LLVM and Clang. IIRC, an earlier version of this derivation used a vendored LLVM. But this was not preferred, because then Hydra had to build another whole other copy of LLVM. It's more efficient to use Nixpkgs' own LLVM build when possible.

In short, I don't think it'll be easy to get rid of LLVM 9. It might be worth getting in touch with the Cling team to see if a new release might be coming soon.

ghost · 2024-01-27T03:18:59Z

Result of nixpkgs-review pr 283989 run on x86_64-linux 1

2 packages built:

cling
xeus-cling

Result of nixpkgs-review pr 283989 run on x86_64-darwin 1

2 packages built:

cling
xeus-cling

ghost · 2024-01-27T03:28:02Z

A few thoughts here, it's been a few years so I don't remember everything perfectly:
* Cling is pretty tightly bound to a given LLVM release, in this case LLVM 9. I don't think you're going to have luck trying to build Cling with a totally different LLVM version.

it builds -- do you have any suggestions on a good way to test? note that the current darwin build is generating errors when run (missing incudes) and this PR seems to get further but generates different errors (finds includes but has unresolved symbols). linux can include iostream and write to cout. that's the extent i've tested.

* Building with Root's LLVM fork could potentially work, but why? You'll just have replaced the current Nixpkgs build of LLVM 9 with another (slightly weird/patched) version.

there is a maintenance burden. LLVM9 is different enough from newer LLVMs that the toolchain requires a bunch of special cases for everything to work. there are some darwin bugs with the current toolchains i'm working on and not having to support older toolchains will make the changes and the code simpler. there is a cost to just leaving things as is.

* Over its history, Cling has sometimes required patches to both LLVM and Clang. IIRC, an earlier version of this derivation used a vendored LLVM. But this was not preferred, because then Hydra had to build another whole other copy of LLVM. It's more efficient to use Nixpkgs' own LLVM build when possible.

given cling is the only package using LLVM9 it already is requiring Hydra to build a whole other LLVM.

In short, I don't think it'll be easy to get rid of LLVM 9. It might be worth getting in touch with the Cling team to see if a new release might be coming soon.

a new version was released in December.

thomasjm · 2024-01-27T03:40:54Z

pkgs/development/interpreters/cling/default.nix

-    chmod -R u+w include
-    git apply ${./fix-llvm-include.patch}
-  '';
+  version = "0.9";


This should probably be 1.0 to pick up the latest support. We may need to ping the Cling team to get them to cut a Git release with a tag.

thomasjm · 2024-01-27T03:42:33Z

a new version was released in december.

Oh, really? They didn't tag it on GitHub. That would change things.

I went digging around and found this: https://github.com/vgvassilev/cling/blob/v1.0/docs/ReleaseNotes.md. It indicates you can build Cling with LLVM 13.

Somewhat confusingly, the build instructions on this page mention a LLVM branch called cling-llvm16 🤔

do you have any suggestions on a good way to test?

A good start would be to run the full sample Jupyter notebook provided by xeus-cling: https://github.com/jupyter-xeus/xeus-cling/blob/main/notebooks/xcpp.ipynb.

wegank · 2024-01-27T03:49:33Z

They did tag the release, it was just oddly announced in vgvassilev's repo.

Also, the official instruction is always to build in-tree with their own fork of LLVM, and building with llvmPackages_13 is likely broken and unsupported anyway (vgvassilev/cling#230).

ghost · 2024-01-27T03:51:00Z

a new version was released in december.

Oh, really? They didn't tag it on GitHub. That would change things.

I went digging around and found this: https://github.com/vgvassilev/cling/blob/v1.0/docs/ReleaseNotes.md. It indicates you can build Cling with LLVM 13.

I was messing around yesterday and put together the derivation below. i got it to build and hello world worked but was pulling header files from my system so still needed work (only tested on x64 linux)

default.nix

{ lib
, stdenv
, cmake
, fetchFromGitHub
, ninja
, python3
, ncurses
, zlib
}:
let
  clingRepo = "cling";
  llvmRepo = "llvm-project";
in
stdenv.mkDerivation (finalAttrs: {
  pname = "cling2"; 
  version = "1.0";
  srcs = let owner = "root-project"; in [
    (fetchFromGitHub {
      inherit owner; 
      repo = clingRepo;
      rev = "refs/tags/v${finalAttrs.version}";
      hash = "sha256-Ye8EINzt+dyNvUIRydACXzb/xEPLm0YSkz08Xxw3xp4=";
      name = clingRepo;
    })
    (fetchFromGitHub {
      inherit owner; 
      repo = llvmRepo;
      #rev = "refs/tags/cling-llvm16-20231130-01";
      #hash = "sha256-h/cstR1z6SLooVcNUvT2FsY53bBsZbU81Wwi9AUZbOIr";
      rev = "refs/tags/cling-llvm13-20231016-01";
      hash = "sha256-Unw5RzYcVYJsViaM9t+QhuBXzTY/r6qo9TDzwZkFi5c=";
      name = llvmRepo;
    })
  ];  
  sourceRoot = ".";
  postUnpack = ''
    chmod u+w -R .
  '';
  strictDeps = true;
  nativeBuildInputs = [
    cmake
    ninja
    python3
  ];
  buildInputs = [
    ncurses
    zlib
  ];
  cmakeDir = "../${llvmRepo}/llvm";
  cmakeFlags = [
    "-DLLVM_BUILD_TOOLS=OFF"
    "-DLLVM_ENABLE_PROJECTS=clang"
    "-DLLVM_EXTERNAL_CLING_SOURCE_DIR=../${clingRepo}"
    "-DLLVM_EXTERNAL_PROJECTS=cling"
    "-DLLVM_TARGETS_TO_BUILD=host;NVPTX"
  ];
  meta = with lib; {
    description = "The Interactive C++ Interpreter";
    homepage = "https://root.cern/cling/";
    license = with licenses; [ lgpl21 ncsa ];
    maintainers = with maintainers; [ thomasjm ];
    platforms = platforms.unix;
  };
})

Somewhat confusingly, the build instructions on this page mention a LLVM branch called cling-llvm16 🤔

using the latest cling rev on main and the the latest cling-llvm16 from the llvm fork will build in the above derivation and hello world works.

I saw @wegank working on this PR and was hoping it would solve all our problems.

do you have any suggestions on a good way to test?

A good start would be to run the full sample Jupyter notebook provided by xeus-cling: https://github.com/jupyter-xeus/xeus-cling/blob/main/notebooks/xcpp.ipynb.

thanks!

wegank · 2024-01-27T03:55:28Z

using the latest cling rev on main and the the latest cling-llvm16 from the llvm fork will build in the above derivation and hello world works.

Oh, great! Would you like to create a PR? I'll close mine in favour of yours.

thomasjm · 2024-01-27T03:56:53Z

Usually when there's uncertainty about how to build I've pinged some Cling people. Historically this has been @vgvassilev or @Axel-Naumann -- any chance one of you could help us pick which version of LLVM to use with Cling these days?

Like I mentioned, if we have to choose between a vendored LLVM and using one that Nixpkgs contains anyway, we usually prefer the latter.

thomasjm · 2024-01-27T03:59:55Z

the official instruction is always to build in-tree with their own fork of LLVM, and building with llvmPackages_13 is likely broken and unsupported anyway (vgvassilev/cling#230).

Ah I see. Well, we've gotten by with unpatched LLVM 9 so far ¯\_(ツ)_/¯. IIRC we did that with Cling maintainer blessing but maybe things have changed.

ghost · 2024-01-27T04:06:19Z

using the latest cling rev on main and the the latest cling-llvm16 from the llvm fork will build in the above derivation and hello world works.

Oh, great! Would you like to create a PR? I'll close mine in favour of yours.

it's not very far along. I can make it a WIP but your PR seems like it is further along. i haven't tried to integrate with xeus-cling.

ghost · 2024-01-27T05:13:02Z

#284167

vgvassilev · 2024-01-27T07:42:08Z

We should use cling v1.0 and llvm13. In principle we can use vanilla llvm but we need our clang because it contains patches that make cling work.

thomasjm · 2024-01-28T11:44:50Z

Thanks @vgvassilev!

Could you tell me where to find the necessary version of Clang? In the past I've used the tagged commits from the repo at http://root.cern/git/clang.git. But this lacks a cling-v1.0 tag -- the latest available is cling-v0.9.

Also, would it be possible to create a GitHub release for the new Cling 1.0 on https://github.com/root-project/cling ?

vgvassilev · 2024-01-28T16:35:20Z

Thanks @vgvassilev!

Could you tell me where to find the necessary version of Clang? In the past I've used the tagged commits from the repo at http://root.cern/git/clang.git. But this lacks a cling-v1.0 tag -- the latest available is cling-v0.9.

We have switched to the llvm monorepo: https://github.com/root-project/llvm-project/ the tag that goes with v1.0 is cling-llvm13. @hahnjo, we might need to create an alias for this tag cling-v1.0 which will have more meaningful relationship between the cling version and the llvm version...

Also, would it be possible to create a GitHub release for the new Cling 1.0 on https://github.com/root-project/cling ?

Done.

RossComputerGuy · 2024-04-07T04:25:10Z

I'm wondering what the progress on this is, I see the linux targets pass but not the darwin ones.

wegank · 2024-04-07T15:16:30Z

The darwin ones should build fine, they were failing on ofborg due to timeout.

thomasjm · 2024-04-08T00:38:32Z

The Linux one is not working yet, it builds but still has some include path issues to resolve.

RossComputerGuy · 2024-04-08T01:09:10Z

The darwin ones should build fine, they were failing on ofborg due to timeout.

That's great.

The Linux one is not working yet, it builds but still has some include path issues to resolve.

Well, we should get those fixed then heh. I'm hoping we can get this merged since it's one of the things I would like to see before LLVM 19 is released. From the looks of it, LLVM 19 will be coming out in July but no rush.

thomasjm · 2024-04-09T01:50:17Z

Okay, turned out to be easier than I thought to fix the flags up. #284865 is ready for review now.

wegank · 2024-04-09T04:36:28Z

Superseded by #284865.

github-actions bot added the 6.topic: jupyter Interactive computing tooling: kernels, notebook, jupyterlab label Jan 26, 2024

wegank force-pushed the cling-llvm branch from 6034505 to e48ccb1 Compare January 26, 2024 12:03

ofborg bot requested a review from thomasjm January 26, 2024 12:26

ofborg bot added 10.rebuild-darwin: 1-10 10.rebuild-linux: 1-10 labels Jan 26, 2024

xeus-cling: use llvm from cling

09a88c1

wegank force-pushed the cling-llvm branch 2 times, most recently from 5ec4e99 to 09636ac Compare January 26, 2024 13:47

ghost mentioned this pull request Jan 26, 2024

LLVM[8-11] Removal Progress Tracker #283954

Closed

cling: vendor llvm

af5769d

wegank force-pushed the cling-llvm branch from 09636ac to af5769d Compare January 26, 2024 18:29

wegank marked this pull request as ready for review January 27, 2024 01:06

thomasjm reviewed Jan 27, 2024

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ghost mentioned this pull request Jan 27, 2024

[WIP] cling: update to latest dev revision #284167

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thomasjm mentioned this pull request Jan 29, 2024

cling: 0.9 -> 1.0 #284865

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wegank closed this Apr 9, 2024

wegank deleted the cling-llvm branch April 9, 2024 04:36

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cling, xeus-cling: vendor llvm #283989

cling, xeus-cling: vendor llvm #283989

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cling, xeus-cling: vendor llvm #283989

cling, xeus-cling: vendor llvm #283989

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