[llvm-branch-commits] [libc++] Annotate classes with _LIBCPP_PFP to enable pointer field protection (PR #151652)

[Peter Collingbourne via llvm-branch-commits]

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@@ -195,3 +195,16 @@ prevent compilers from generating said debug information. Aliases inside type tr
 should be annotated for the same reason.
 
 This is enforced by the clang-tidy check ``libcpp-nodebug-on-aliases``.
+
+Pointer field protection
+========================
+
+To improve the effectiveness of Clang's `pointer field protection
+<https://clang.llvm.org/docs/StructureProtection.html>`_ feature,
+commonly used vocabulary types with pointer fields are marked with the
+``_LIBCPP_PFP`` attribute, to give Clang permission to use PFP to protect
+their pointer fields. Newly added vocabulary types should be marked with
+this attribute if they contain pointer fields.
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pcc wrote:

That was an oversight; now added.

Technically, `basic_string::__long` is the type that needs to be annotated because that's the one with a pointer field, so that's what I did. I also improved the wording here to clarify that internal base classes and fields need the annotations if they have pointer fields.

https://github.com/llvm/llvm-project/pull/151652