[libc] Support C23 binary notation in `sprintf`

[SchrodingerZhu]

see https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2612.pdf

[michaelrj-google]

This should be fairly straightforward if you'd like to implement it.

You'll need to add the new format in the int converter (here: https://github.com/llvm/llvm-project/blob/main/libc/src/stdio/printf_core/int_converter.h#L32) based on IntegerToString<Bin> (here: https://github.com/llvm/llvm-project/blob/main/libc/src/__support/integer_to_string.h#L156).

You'll also need to add b and B as conversion name options in the main converter switch statement (here: https://github.com/llvm/llvm-project/blob/main/libc/src/stdio/printf_core/converter.cpp#L55) and in the parser (here: https://github.com/llvm/llvm-project/blob/main/libc/src/stdio/printf_core/parser.h#L156 and here: https://github.com/llvm/llvm-project/blob/main/libc/src/stdio/printf_core/parser.h#L481)

[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. In the comments of the issue, request for it to be assigned to you.
2. Fix the issue locally.
3. 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.
4. Create a Git commit.
5. Run git clang-format HEAD~1 to format your changes.
6. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation.

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: Schrodinger ZHU Yifan (SchrodingerZhu)

see https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2612.pdf

[agentcooper]

Ah, I didn't notice that @Rajveer100 already sent a PR for this. Although it seems that our implementations are somewhat different.

[Rajveer100]

Hey @agentcooper!

It would be great if you could help me land my PR if you are fine with that!

Currently, it's not fully done though, looks like your implementation is complete?

[michaelrj-google]

I've looked over both patches and @agentcooper's looks more complete so I put my review there. Feel free to collaborate on finishing this. There's a libc channel in the LLVM discord which is a good place to chat about libc.

[Rajveer100]

Absolutely, no worries! I would love to learn from the changes!