[Clang] Missing flag to allow using `[[gnu::init_priority]]` in source files

[philnik777]

Currently it's not possible to use [[gnu::init_priority(100)]] in source files except by using line control markers. It would be way nicer if there was a diagnostic group to disable this with the diagnostic being an error by default. GCC currently accepts this with a warning without a group instead, which is also annoying, but not as bad as making it only possible with a hack.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Nikolas Klauser (philnik777)

Currently it's not possible to use `[[gnu::init_priority(100)]]` in source files except by using line control markers. It would be way nicer if there was a diagnostic group to disable this with the diagnostic being an error by default. GCC currently accepts this with a warning without a group instead, which is also annoying, but not as bad as making it only possible with a hack.

[shafik]

CC @erichkeane

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Nikolas Klauser (philnik777)

Currently it's not possible to use `[[gnu::init_priority(100)]]` in source files except by using line control markers. It would be way nicer if there was a diagnostic group to disable this with the diagnostic being an error by default. GCC currently accepts this with a warning without a group instead, which is also annoying, but not as bad as making it only possible with a hack.

[erichkeane]

Repro: https://godbolt.org/z/4T7ecxvjT

I think it is perfectly reasonable to emit the same warning (with a warning group of course) as GCC for this situation. This is likely a very simple fix, so I'll mark this as a good first issue. This should be a very simple addition of a diagnostic, then changing the handler to just emit the warning instead.

[el-ev]

Hello, I'm new here and I would like to work on this.

[erichkeane]

Assigned! Please let me know if you have trouble with this, and let me know when you give up on this so others can take this.