Everything to alter is in lifetime.d. It would be trivial to create this.
https://issues.dlang.org/show_bug.cgi?id=13988
The only thing is to have a malloc-based AA for tracking
https://github.com/D-Programming-Language/druntime/blob/18d57ffe3eed8674ca2052656bb3f410084379f6/src/rt/util/container/hashtab.d
However, note that this wouldn't track allocations that the compiler did for closures.
Plain _d_allocmemory.
