Checker for nvlist

Hello,
I'm looking at SimpleStreamChecker and trying to check that each
nvlist_alloc call has nvlist_free at the end), but can't find a way how to
map nvlist value for postcall and precall:
        nvlist_alloc(&nv, NV_UNIQUE_NAME, 0);
        ...

  nvlist_free(nv);

as clang understand "&nv" for nvlist_alloc and "nv" for nvlist_free as
various data. Any hint, please?

Well, I solved this.
But next question:

if (nvlist_alloc(....) !=0) {
      return (NULL);
}

How tell to checker that this block doesn't require nvlist_free or bypass
this return? (without assert handlers, exactly in checker code)

Cheers,
J