[libc-commits] [libc] [libc] implement `strings/ffs` (PR #129892)

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c8ef wrote:

Thanks for your detailed and patient review!

> On the side note, probably we will need to revise other `stdbit` functions to see if there are any other issues with them, as what you found with `first_trailing_one`.

Will do in a sec.

https://github.com/llvm/llvm-project/pull/129892