Fixes for compiling with GCC 15 (Fedora 42)

[ellert]

This Pull request:

These changes make it possible to compile root 6.34.02 using gcc 15 on Fedora 42.

Also the following commits need to be backported from master:

commit 2884f67
commit cfc9221

... and the following commits from LLVM:

commit llvm/llvm-project@7e44305
commit llvm/llvm-project@7abf440 (see PR llvm/llvm-project#123320)

[github-actions]

Test Results

    18 files      18 suites   3d 21h 22m 51s ⏱️
 2 685 tests  2 662 ✅ 23 💤 0 ❌
46 606 runs  46 606 ✅  0 💤 0 ❌

Results for commit 3357643.

♻️ This comment has been updated with latest results.

[hageboeck]

Hi @ellert,

thanks for the initiative!

We have a few things to deal with:

1. Would you mind running git-clang-format on the "conflicting functions" commit?
2. Regarding the LLVM includes, we were already discussing in ROOT doesn't compile with gcc-15 #17444 and Add missing include to X86MCTargetDesc.h llvm/llvm-project#123320, but the situation is a bit complicated:

• In order not to deviate from llvm (which allows for much faster future upgrades), we are not simply committing to the llvm tree.
• Instead, we try to upstream patches to llvm, and backport afterwards. This will make them disappear during a rebase. (This is why there is a CI failure.)
• For this reason, we have to wait for Add missing include to X86MCTargetDesc.h llvm/llvm-project#123320 and backport.

Number 2 is a slow process, but we are working on it. So if you want to get out of this in a timely manner, I would propose to retain and clang-format the "conflicting functions" commit, and remove the LLVM commit. This way, we can merge this PR quickly, and we'll take care of the llvm business.

Let us know what you think.

[hageboeck]

@devajithvs FYI

[ellert]

@hageboeck

I ran git-clang-format as reqested.
I dropped the commit with the LLVM changes from the PR and edited to description to include references to the LLVM commit and pending PR that provides the same changes (adding #include <cstdint> to two LLVM files).

[hageboeck]

Great, thank you!

The LLVM commits are on their way, and we'll take care of putting all of these changes into the next release.
I'm just waiting for one last CI job before merging.