[libcxx-commits] [PATCH] D145628: [ASan][libcxx] A way to turn off annotations for containers with a specific allocator

[Nikolas Klauser via Phabricator via libcxx-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG2fa1bec7a20b: [ASan][libcxx] A way to turn off annotations for containers with a specific… (authored by AdvenamTacet, committed by philnik).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D145628/new/

https://reviews.llvm.org/D145628

Files:
  libcxx/docs/UsingLibcxx.rst
  libcxx/include/__memory/allocator_traits.h


Index: libcxx/include/__memory/allocator_traits.h
===================================================================
--- libcxx/include/__memory/allocator_traits.h
+++ libcxx/include/__memory/allocator_traits.h
@@ -401,6 +401,25 @@
     : __is_cpp17_move_insertable<_Alloc>
 { };
 
+// ASan choices
+#ifndef _LIBCPP_HAS_NO_ASAN
+#   define _LIBCPP_HAS_ASAN_CONTAINER_ANNOTATIONS_FOR_ALL_ALLOCATORS 1
+#endif
+
+#ifdef _LIBCPP_HAS_ASAN_CONTAINER_ANNOTATIONS_FOR_ALL_ALLOCATORS
+template <class _Alloc>
+struct __asan_annotate_container_with_allocator
+#   if defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 1600
+      : true_type {};
+#   else
+      // TODO LLVM18: Remove the special-casing
+      : false_type {};
+#   endif
+
+template <class _Tp>
+struct __asan_annotate_container_with_allocator<allocator<_Tp> > : true_type {};
+#endif
+
 #undef _LIBCPP_ALLOCATOR_TRAITS_HAS_XXX
 
 _LIBCPP_END_NAMESPACE_STD
Index: libcxx/docs/UsingLibcxx.rst
===================================================================
--- libcxx/docs/UsingLibcxx.rst
+++ libcxx/docs/UsingLibcxx.rst
@@ -523,3 +523,32 @@
 versions. This allows the library to have better estimates for newly introduced
 Unicode code points, without requiring the user to use the latest C++ version
 in their code base.
+=======
+Turning off ASan annotation in containers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``__asan_annotate_container_with_allocator`` is a customization point to allow users to disable
+`Address Sanitizer annotations for containers <https://github.com/google/sanitizers/wiki/AddressSanitizerContainerOverflow>`_ for specific allocators. This may be necessary for allocators that access allocated memory.
+This customization point exists only when ``_LIBCPP_HAS_ASAN_CONTAINER_ANNOTATIONS_FOR_ALL_ALLOCATORS`` Feature Test Macro is defined.
+
+For allocators not running destructors, it is also possible to `bulk-unpoison memory <https://github.com/google/sanitizers/wiki/AddressSanitizerManualPoisoning>`_ instead of disabling annotations altogether.
+
+The struct may be specialized for user-defined allocators. It is a `Cpp17UnaryTypeTrait <http://eel.is/c++draft/type.traits#meta.rqmts>`_ with a base characteristic of ``true_type`` if the container is allowed to use annotations and ``false_type`` otherwise.
+
+The annotations for a ``user_allocator`` can be disabled like this:
+
+.. code-block:: cpp
+
+  #ifdef _LIBCPP_HAS_ASAN_CONTAINER_ANNOTATIONS_FOR_ALL_ALLOCATORS
+  template <class T>
+  struct std::__asan_annotate_container_with_allocator<user_allocator<T>> : std::false_type {};
+  #endif
+
+Why may I want to turn it off?
+------------------------------
+
+There are a few reasons why you may want to turn off annotations for an allocator.
+Unpoisoning may not be an option, if (for example) you are not maintaining the allocator.
+
+* You are using allocator, which does not call destructor during deallocation.
+* You are aware that memory allocated with an allocator may be accessed, even when unused by container.


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