MPL Bytecode Compiler Code

11 lines (8 with data), 252 Bytes

heap=0
usevec(v,n) [heap=v;!v=n<<1;v!n=0]
memused(;p,r) [r=0;p=heap;!p@!p<0?[r-=!p;p-=!p],p+=!p;r]
getvec(n;v,r) [
  n=(n+2)<<1;v=heap;
  !v@[!v<0@v-=!v;r=v;!v>0@v+=!v;!r=v-r;n<=!r?[!(r+n)=!r-n;!r=-n;=r+2]]
]
freevec(v) v?v!-1<0?v!-1=-v!-1