From jrmalloc’s documents, I understand that there are some non-standad API like mallocx. Calling such API which a MALLOCX_ARENA flag one can specify which arena the alloc happens.

However, in C++, memory allocations happens more “automaticly” and “implicitly”. Consider:

1. A object can be allocated by new rather than malloc functions. In this case, how can I pass the MALLOCX_ARENA flag to new?
2. Memory allocation may happen implicitly. For example by vector::emplace_back or make_shared.

I wonder how to specify which arena to use in C++. I guess we have to implement some allocators, however, I am quite unfamiliar with that.