AddressSanitizer: container-overflow false positive

[tttapa]

The following code using a polymorphic memory resource causes a false positive for the container-overflow check in the address sanitizer:

https://godbolt.org/z/9q596WG1d

#include <array>
#include <memory_resource>
#include <numeric>
#include <vector>

int main() {
    std::array<unsigned char, 1024> buffer;
    std::pmr::monotonic_buffer_resource mbr {buffer.data(), buffer.size()};
    std::pmr::vector<int> vec {&mbr};
    vec.reserve(16);
    return std::accumulate(buffer.begin(), buffer.end(), int {});
}

clang++-18 -fsanitize=address -O0 -stdlib=libc++

The code uses an array as a buffer, and allocates a vector into that buffer. Then it accesses all bytes of the buffer.
AFAICT, accessing the bytes of the buffer is not UB, but the reason why this fails is that there also happens to be a reserved vector in that storage, and Asan thinks we're accessing beyond the initialized memory of the vector.

This may be challenging to work around, though. I guess Asan just marks those bytes as belonging to the vector, and it may be hard to tell whether the bytes are accessed directly through the vector's iterators, or through other (possibly valid) means.