llvm-18-linker-tools does not include LLVMgold.so

[Paul Meckel]

[ Impact ]

* User can't use clang++-18 to build C++ code with -flto option.

[ Test Plan ]

* Install clang-18 from proposed updates.
* Try to build a C++ program with LTO (for example following the steps in original description.

[ Where problems could occur ]

* The missing LLVMgold.so is caused by switching to use mold in package building. Using mold is introduced in llvm 18. The fix is just to revert the change, and uses the same linker (gold) as old llvm versions. So the change looks safe.

[ Other Info ]

* No

[Original Description]

Unlike all other llvm-*-linker-tools packages, this one does not install `/usr/lib/llvm-18/lib/LLVMgold.so`. It does however install a broken symlink to it at `/usr/lib/bfd-plugins/LLVMgold-18.so`
This results in compilation failures with clang++ when used with the `-flto` flag for link time optimization.

To reproduce:

main.cpp:
```c++
int main() { return 0; }
```

```bash
clang++ -flto main.cpp -o main
```

Results in:
```
/usr/bin/ld: /usr/lib/llvm-18/bin/../lib/LLVMgold.so: error loading plugin: /usr/lib/llvm-18/bin/../lib/LLVMgold.so: cannot open shared object file: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
```

Package version is

llvm-18-linker-tools/noble,now 1:18.1.3-1 amd64

llvm-18-linker-tools:
  Installed: 1:18.1.3-1
  Candidate: 1:18.1.3-1
  Version table:
 *** 1:18.1.3-1 500
        500 http://de.archive.ubuntu.com/ubuntu noble/universe amd64 Packages
        100 /var/lib/dpkg/status

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Gianfranco Costamagna (costamagnagianfranco)]

Oracular is not really fixed, llvmGOLD.so is still not built on riscv64.

[Shengjing Zhu (zhsj)]

> llvmGOLD.so is still not built on riscv64

It's not been built from previous versions on riscv64 as well. So at least not a regression.

[Matthias Klose (doko)]

gold is not support upstream on riscv64

[Balint Reczey (rbalint)]

Please backport the fix to Noble.

[Shengjing Zhu (zhsj)]

MP is https://code.launchpad.net/~zhsj/ubuntu/+source/llvm-toolchain-18/+git/llvm-toolchain-18/+merge/466494 and PPA for testing https://launchpad.net/~zhsj/+archive/ubuntu/bug2064187/+packages

The build takes several days and now finally succeeds.

[Shengjing Zhu (zhsj)]

FTR, the fix in Debian/Oracular is at https://launchpad.net/ubuntu/+source/llvm-toolchain-18/1:18.1.5-1 and https://launchpad.net/ubuntu/+source/llvm-toolchain-18/1:18.1.5-3 (LP show riscv64 is failed on version 1:18.1.5-3 but that's not packaging issue, rather LP builder issue. This version is successfully to be built on Debian/riscv64 https://buildd.debian.org/status/logs.php?pkg=llvm-toolchain-18&arch=riscv64)

The relevant commits that need to be backported are

https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/-/commit/7204c780c8756378921cd14cb73d53794f81f3f6
https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/-/commit/72950dbd0f05bd9fe076535e14de522713be98f8
https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/-/commit/898f4588144f8ede8605b7140f8e7f64ee4b0f67

[Gianfranco Costamagna (costamagnagianfranco)]

Thanks, will sponsor. I would have preferred a versioning not like ubuntu1 but ubuntu1.24.04.1, but since
there were never ubuntu1 version, I guess it is fine, specially because oracular has already a newer version.

[Gianfranco Costamagna (costamagnagianfranco)]

and uploaded.

[Simon Quigley (tsimonq2)]

Unsubscribing sponsors, please feel free to re-subscribe if another iteration is needed.

[Timo Aaltonen (tjaalton)]

-1ubuntu0.1 would've been perfect for the first SRU, but not a reason to reject.

[Timo Aaltonen (tjaalton)]

Hello Paul, or anyone else affected,

Accepted llvm-toolchain-18 into noble-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/llvm-toolchain-18/1:18.1.3-1ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-noble to verification-done-noble. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-noble. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Oliver Kuckertz (mologie)]

I successfully tested llvm-18-linker-tools 1:18.1.3-1ubuntu1. Thanks to everyone involved for addressing this issue!

The proposed package for noble resolves the issue for me with an in-house application. Additionally I tested that the simple steps to reproduce in the bug description no longer reproduce the issue, and that the symlink at /usr/lib/bfd-plugins/LLVMgold-18.so is now valid.

[Andreas Hasenack (ahasenack)]

The dep8 tests was stuck, and the details page showed a tmpfail. I retrigered it.

[Launchpad Janitor (janitor)]

This bug was fixed in the package llvm-toolchain-18 - 1:18.1.3-1ubuntu1

---------------
llvm-toolchain-18 (1:18.1.3-1ubuntu1) noble; urgency=medium

  * Disable mold for all to make sure it builds gold (LP: #2064187)
  * Be explicit with what ships in llvm-18-linker-tools to make sure we always
    ship gold

 -- Shengjing Zhu <email address hidden> Mon, 27 May 2024 16:26:20 +0800

[Łukasz Zemczak (sil2100)]

The verification of the Stable Release Update for llvm-toolchain-18 has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.