[libcxx-commits] [libcxx] [libc++][hardening] Check bounds on arithmetic in __bounded_iter (PR #78876)

[David Benjamin via libcxx-commits]

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@@ -151,6 +162,10 @@ struct __bounded_iter {
   }
 
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __bounded_iter& operator-=(difference_type __n) _NOEXCEPT {
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
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davidben wrote:

The problem is that requires negating `__n`, which may hit UB in itself. :-(

https://github.com/llvm/llvm-project/pull/78876