[libcxx-commits] [libcxx] [libc++][Docs] Document `std::optional` hardening (PR #218173)

[Nikolas Klauser via libcxx-commits]

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@@ -440,6 +440,12 @@ CMake configuration time. The available options are:
 
   ABI impact: changes the iterator type of ``std::array``, its size and its layout.
 
+- ``_LIBCPP_ABI_BOUNDED_ITERATORS_IN_OPTIONAL`` -- changes the iterator type of ``std::optional`` to a
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philnik777 wrote:

This macro is also missing an entry in `ABIGuarantees.rst`.

https://github.com/llvm/llvm-project/pull/218173