[libcxx-commits] [libcxx] [libc++] Add the __is_replaceable type trait (PR #132408)

[Louis Dionne via libcxx-commits]

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@@ -754,13 +755,20 @@ public:
   // 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.
+  //
+  // However, it is replaceable since implementing move-assignment as a destroy + move-construct
+  // will maintain the right ASAN state.
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ldionne wrote:

`__is_replaceable` means that you can destroy + move construct instead of assigning. This is orthogonal to whether performing those steps is equivalent to `memcpy` (which in the case of an ASAN-ified `string`, it isn't).

https://github.com/llvm/llvm-project/pull/132408