std::deque details vary by implementation and is largely considered unusable for MSVC. MSVC uses a too small block size making it worthless. libc++ block size

std::deque details vary by implementation and is largely considered unusable for MSVC. MSVC uses a too small block size making it worthless. libc++ block size is 16 elements or 4096 bytes. It is generally better to use a container you can actually understand the implementation details and control. I would not call it a variant of std::deque myself. Not wrong. But not a helpful observation imho.