Add release note for #95264

[ldionne]

No description provided.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Louis Dionne (ldionne)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/96116.diff

1 Files Affected:

• (modified) libcxx/docs/ReleaseNotes/18.rst (+9)

diff --git a/libcxx/docs/ReleaseNotes/18.rst b/libcxx/docs/ReleaseNotes/18.rst
index 7ea13e6943dd4..3e19e7c33f6af 100644
--- a/libcxx/docs/ReleaseNotes/18.rst
+++ b/libcxx/docs/ReleaseNotes/18.rst
@@ -328,6 +328,15 @@ ABI Affecting Changes
   done to fix `#70494 <https://github.com/llvm/llvm-project/issues/70494>`_ and the vendor communication is handled
   in `#70820 <https://github.com/llvm/llvm-project/issues/70820>`_.
 
+- LLVM 18.1.8 Fixed an issue that caused ``std::string`` to pass an incorrect size to ``allocator_traits::deallocate``
+  when deallocating memory. The impact is different depending on a few factors:
+  - Users who don't use a custom allocator in ``std::string`` and don't enable sized deallocation (which is
+    off by default in Clang 18) will not be affected. This is expected to be the vast majority of users.
+  - Users who don't use a custom allocator in ``std::string`` but are enabling sized deallocation (e.g. with
+    ``-fsized-deallocation``) will notice that ``operator delete(void*, size_t)`` is now being passed the correct
+    size. This likely has no impact if they were not customizing ``operator delete``.
+  - Users who use a custom allocator in ``std::string`` will notice that they now get passed the correct allocation
+    size upon deallocation.
 
 Build System Changes
 --------------------

[ldionne]

Gentle ping @tstellar, do we want to merge this?

The CI issues are unrelated.

[tstellar]

We don't have a great way to add release notes after the final release. I added this to the release announcement do you think that is enough?

[ldionne]

We don't have a great way to add release notes after the final release. I added this to the release announcement do you think that is enough?

Yes I think that is fine.