Function lua_setupvalue

depends/lua/src/lapi.c:1236–1254

LUA_API const char *lua_setupvalue (lua_State *L, int funcindex, int n) {
  const char *name;
  TValue *val = NULL;  /* to avoid warnings */
  CClosure *owner = NULL;
  UpVal *uv = NULL;
  StkId fi;
  lua_lock(L);
  fi = index2addr(L, funcindex);
  api_checknelems(L, 1);
  name = aux_upvalue(fi, n, &val, &owner, &uv);
  if (name) {
    L->top--;
    setobj(L, val, L->top);
    if (owner) { luaC_barrier(L, owner, L->top); }
    else if (uv) { luaC_upvalbarrier(L, uv); }
  }
  lua_unlock(L);
  return name;
}


static UpVal **getupvalref (lua_State *L, int fidx, int n) {