[libcxx-commits] [libcxx] [libc++] Add _LIBCPP_NO_SANITIZE for std::__assume_aligned (PR #220296)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Sharjeel Khan (Sharjeel-Khan)

<details>
<summary>Changes</summary>

std::assume_aligned takes void* from __builtin_assume_aligned and converts it _Tp* that causes cfi-unrelated-cast to consider it a downcast leding to CFI checks. Since std::find_if calls std::assume_aligned on __last, it will lead to CFI check that dereferences __last causing a failure. Based on discussion, we can just add _LIBCPP_NO_SANITIZE for cfi-unrelated-cast because it might reject well-defined behavior.

Fix: https://github.com/llvm/llvm-project/issues/219306

---
Full diff: https://github.com/llvm/llvm-project/pull/220296.diff


1 Files Affected:

- (modified) libcxx/include/__memory/assume_aligned.h (+1-1) 


``````````diff
diff --git a/libcxx/include/__memory/assume_aligned.h b/libcxx/include/__memory/assume_aligned.h
index 08f1772cd6dfa..d39d955200271 100644
--- a/libcxx/include/__memory/assume_aligned.h
+++ b/libcxx/include/__memory/assume_aligned.h
@@ -23,7 +23,7 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <size_t _Np, class _Tp>
-[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _Tp* __assume_aligned(_Tp* __ptr) {
+[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _LIBCPP_NO_SANITIZE("cfi-unrelated-cast") _Tp* __assume_aligned(_Tp* __ptr) {
   static_assert(_Np != 0 && (_Np & (_Np - 1)) == 0, "std::assume_aligned<N>(p) requires N to be a power of two");
 
   if (__libcpp_is_constant_evaluated()) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/220296