[libcxx-commits] [libcxx] [libc++] Fix UB in bitwise logic of {std, ranges}::{fill, fill_n} algorithms (PR #122410)

[Louis Dionne via libcxx-commits]

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@@ -69,12 +72,47 @@ constexpr void test_iterators() {
     {
       std::array<int, 0> a;
       auto range = std::ranges::subrange(It(a.data()), Sent(It(a.data())));
-      auto ret = std::ranges::fill(range, 1);
+      auto ret   = std::ranges::fill(range, 1);
       assert(base(ret) == a.data());
     }
   }
 }
 
+// The `ranges::{fill, fill_n}` algorithms require `vector<bool, Alloc>::iterator` to satisfy the
+// `std::indirectly_writable` concept when used with `vector<bool, Alloc>`, which is only met since C++23.
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ldionne wrote:

Same here, let's add a comment with a link to the PR.

https://github.com/llvm/llvm-project/pull/122410