The return value of `column()` obtained from `std::source_location::current()` should be documented

[frederick-vs-ja]

Per standard requirements (N4868 [source.srcloc.cons]/1.1, N4868 [support.srcloc.obs]/2), the return value of column() obtained from std::source_location::current() is implementation-defined and thus should be documented.

Currently, __builtin_COLUMN and __builtin_source_location are mentioned in this page, but their values are not well-documented.

Documentations of implementations would be helpful when one wants use column(), as there's implementation divergence (can be found in this test file in MSVC STL).

[komalverma04]

I will work on it today.

[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: A. Jiang (frederick-vs-ja)

Per standard requirements ([N4868 [source.srcloc.cons]/1.1](https://timsong-cpp.github.io/cppwp/n4868/support.srcloc.cons#1.1), [N4868 [support.srcloc.obs]/2](https://timsong-cpp.github.io/cppwp/n4868/support.srcloc.obs#2)), the return value of `column()` obtained from `std::source_location::current()` is implementation-defined and thus should be documented.

Currently, __builtin_COLUMN and __builtin_source_location are mentioned in this page, but their values are not well-documented.

Documentations of implementations would be helpful when one wants use column(), as there's implementation divergence (can be found in this test file in MSVC STL).

[GeorgeKA]

Hello. No one appears to be assigned or working on this. Can it be assigned to me?

[GeorgeKA]

Hi @cor3ntin & @frederick-vs-ja . Checking if this is an issue that's still active. I'd be happy to work on it if so.