[libcxx-commits] [libcxx] [ASan][libc++] Annotating `std::basic_string` with all allocators (PR #75845)

[via libcxx-commits]

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@@ -1891,8 +1891,7 @@ private:
 #if !defined(_LIBCPP_HAS_NO_ASAN) && defined(_LIBCPP_INSTRUMENTED_WITH_ASAN)
     const void* __begin = data();
     const void* __end   = data() + capacity() + 1;
-    if (!__libcpp_is_constant_evaluated() && __begin != nullptr &&
-        is_same<allocator_type, __default_allocator_type>::value)
+    if (!__libcpp_is_constant_evaluated() && __asan_annotate_container_with_allocator<allocator_type>::value)
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EricWF wrote:

What happens when the string is created in a constant expression, and then read outside of one? LIke this?
```
#include <string>

constexpr std::string s = "abcdef";

 // launder 's' through a non-constexpr function
std::string const&  hide() { return s; }

/* not constinit */ std::string s2 = hide();

int main() {
    return s2 == "abcdef"; // Boom?
}
```
https://godbolt.org/z/3c9K4f8cq #

https://github.com/llvm/llvm-project/pull/75845