[gcc r14-9300] doc: update [[gnu::no_dangling]]

[Marek Polacek]

https://gcc.gnu.org/g:a89c5df317d1de74871e2a05c36aed9cbbb21f42

commit r14-9300-ga89c5df317d1de74871e2a05c36aed9cbbb21f42
Author: Marek Polacek <polacek@redhat.com>
Date:   Mon Mar 4 11:25:28 2024 -0500

    doc: update [[gnu::no_dangling]]
    
    ...to offer a more realistic example.
    
    gcc/ChangeLog:
    
            * doc/extend.texi: Update [[gnu::no_dangling]].

Diff:
---
 gcc/doc/extend.texi | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index f679c81acf2..df0982fdfda 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -29370,7 +29370,8 @@ Or:
 
 @smallexample
 template <typename T>
-[[gnu::no_dangling(std::is_reference_v<T>)]] int& foo (T& t) @{
+[[gnu::no_dangling(std::is_lvalue_reference_v<T>)]]
+decltype(auto) foo(T&& t) @{
   @dots{}
 @};
 @end smallexample