How to link Debug version of libc++

I want to enable assert in stanard library (such as index check in std::vector), and I defined _LIBCPP_DEBUG=1(https://libcxx.llvm.org/docs/DesignDocs/DebugMode.html#using-debug-mode) to enable debug mode of libc++, but found no debug functions in libc++ system provided. So How can I enable debug mode or where can I get the debug lib of libc++