[libcxx-commits] [libcxx] [ASan][libc++] Turn off SSO annotations for Apple platforms (PR #96269)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Tacet (AdvenamTacet)

<details>
<summary>Changes</summary>

This commit disables short string AddressSanitizer annotations on Apple platforms as a temporary solution to the problem reported in issue #<!-- -->96099.

For more information on Apple's block implementation, please refer to [`clang/docs/Block-ABI-Apple.rst`](https://github.com/llvm/llvm-project/blob/main/clang/docs/Block-ABI-Apple.rst). The core issue lies in the fact that blocks are unaware of their content, causing AddressSanitizer errors when blocks are moved using `memmove`.

I believe - and I'm not alone - that the issue should ideally be addressed within the block moving logic. However, if a timely resolution is not feasible, this temporary fix can be used. Before merging, we should ensure that a more permanent solution cannot be implemented in time and that this change effectively resolves the issue.

---
Full diff: https://github.com/llvm/llvm-project/pull/96269.diff


1 Files Affected:

- (modified) libcxx/include/string (+4) 


``````````diff
diff --git a/libcxx/include/string b/libcxx/include/string
index 56307b391a3e5..6b442c51c607f 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -1930,6 +1930,10 @@ private:
     (void)__old_mid;
     (void)__new_mid;
 #if !defined(_LIBCPP_HAS_NO_ASAN) && defined(_LIBCPP_INSTRUMENTED_WITH_ASAN)
+  #if defined(__APPLE__)
+    if(!__is_long())
+      return;
+  #endif
     std::__annotate_contiguous_container<_Allocator>(data(), data() + capacity() + 1, __old_mid, __new_mid);
 #endif
   }

``````````

</details>


https://github.com/llvm/llvm-project/pull/96269