[libcxx-commits] [libcxx] [libc++][math] Add missing `constexpr since C++23` comment for signbit (PR #212458)

[Lucas Mellone via libcxx-commits]

https://github.com/lknknm created https://github.com/llvm/llvm-project/pull/212458

Adds the missing `// constexpr since C++23` for `std::signbit` in `cmath` documentation.
Follows-up: https://github.com/llvm/llvm-project/pull/105946.

>From 3cb65170b15cbfa36b2504199ecdfaea0d661787 Mon Sep 17 00:00:00 2001
From: Lucas Mellone <github.snugness349 at passinbox.com>
Date: Tue, 28 Jul 2026 12:55:50 +0200
Subject: [PATCH] add: constexpr since C++23 comment for signbit

---
 libcxx/include/cmath | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libcxx/include/cmath b/libcxx/include/cmath
index 992854b0490a3..4d91c34c48bec 100644
--- a/libcxx/include/cmath
+++ b/libcxx/include/cmath
@@ -136,7 +136,7 @@ long double    tanhl(long double x);
 
 //  C99
 
-bool signbit(arithmetic x);
+bool signbit(arithmetic x); // constexpr since C++23
 
 int fpclassify(arithmetic x); // constexpr since C++23