[libcxx-commits] [libcxx] [ASan][libc++] Turn on ASan annotations for short strings (PR #79536)

[Nikolas Klauser via libcxx-commits]

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@@ -736,10 +735,44 @@ public:
   //
   // This string implementation doesn't contain any references into itself. It only contains a bit that says whether
   // it is in small or large string mode, so the entire structure is trivially relocatable if its members are.
+#if !defined(_LIBCPP_HAS_NO_ASAN) && defined(_LIBCPP_INSTRUMENTED_WITH_ASAN)
+  // When compiling with AddressSanitizer (ASan), basic_string cannot be trivially
+  // relocatable. Because the object's memory might be poisoned when its content
+  // is kept inside objects memory (short string optimization), instead of in allocated
+  // external memory. In such cases, the destructor is responsible for unpoisoning
+  // the memory to avoid triggering false positives.
+  // Therefore it's crucial to ensure the destructor is called
+  using __trivially_relocatable = false_type;
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philnik777 wrote:

Maybe there needs to be some ASan handling when relocating objects? We're destroying objects after all, which should probably poison memory.

https://github.com/llvm/llvm-project/pull/79536