[libc-commits] [libc] [libc][stdbit] implement stdc_trailing_ones (C23) (PR #80459)

[Nick Desaulniers via libc-commits]

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@@ -55,6 +85,20 @@ inline unsigned stdc_leading_ones(unsigned long long x) {
       unsigned: stdc_leading_ones_ui,                                          \
       unsigned long: stdc_leading_ones_ul,                                     \
       unsigned long long: stdc_leading_ones_ull)(x)
+#define stdc_trailing_zeros(x)                                                 \
+  _Generic((x),                                                                \
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nickdesaulniers wrote:

> Hey! Thanks for doing this.

Heh, thanks for standardizing these.  I was going to show you/ask for review at some point, I appreciate that you found this, took a look, and had feedback.  Do you have cycles at the moment to be cc'ed on more of these as I implement them? If not, no worries.

This is the first I've heard of `_BitInt`, is that something new-ish?

> 6.2.5 Types
> A bit-precise signed integer type is designated as _BitInt(N) where N is an integer constant expression
that specifies the number of bits that are used to represent the type, including the sign bit. Each
value of N designates a distinct type.42)

Yeah, woah gcc-14 and clang-14 both support this type...https://godbolt.org/z/or83fMcro 

Ok, I will add support for these. Will file an TODO and revisit; the initial implementations don't need to be perfect to land.

https://github.com/llvm/llvm-project/pull/80459