Return function issue

[Arkan]

Hello
I have a question, for example, look at these functions:

function Spawn takes integer i returns unit
  local unit u = CreateUnit(...)
  return u
endfunction

function test1 takes nothing returns nothing
  call Spawn(1)
endfunction

function test2 takes nothing returns nothing
  local unit u = Spawn(1)
endfunction

I notice both test1 and test2 works, only the unit is stored in a variable in test2. My question is now, if I were to use test1, would it cause any leaks because I'm not using the returned unit? I'm guessing no but I'm asking just to be on the safe side.

 

[AdamGriffith]

Well why the hell would you do that? ^^
And you wont be able to null u.
And locals that extend handles have to be nulled.

 

[Infinitegde]

And what he means is Yes, you still do have to null it. After all, it's exactly like Create unit except your calling it, and losing reference to the variable. And that is always bad

 

[Flare]

Well, if that unit is a dummy unit, then you're probably screwed since you have no variable to refer back to it for applying an expiration timer (or whatever your method of getting rid of dummies would be).

If it's a normal in-game unit (like a Footman), then you're fine, since they will, more than likely, end up dead and get removed naturally.

And locals that extend handles have to be nulled.

That's a fairly small thing. Not the best coding practise to leave it go un-nulled, but it's far from game-breaking, even in big numbers. You can just do

//Short and simple method
return CreateUnit (...)
//Or drawn-out method
local unit u = CreateUnit (...)
set globalunit = u
set u = null
return globalunit

 

[quraji]

function c takes nothing returns unit
    return CreateUnit(...)  //  no reference leak, since the unit isn't stored in a variable
endfunction

function b takes nothing returns unit
    local unit u = c()
    return u  //  leaks a reference (u), because you can't null after a return
endfunction

function a takes nothing returns nothing
    local unit u = b()    //  causes a reference leak since b didn't null a handle
    local unit u2 = c()  //  no leak since c returned the value directly
    //do stuff
    set u = null    //  cleanup
    set u2 = null  //  cleanup
endfunction

If the function returns a handle value directly, there is no leak as long as you clean it up in the function that called it (this holds true for any number of functions). But if you store the value in a local variable anywhere and do not null it, that will cause a reference leak.
This is going to happen in most cases since usually you manipulate the handle, you don't just create and return it. At this point you'd use a workaround, one of which Flare mentioned.

Another workaround is this one that I posted in a previous thread like this...it's fun for all:

function b takes unit u (, takes other stuff like coordinates) returns unit
   set u = CreateUnit(...)
   //  do stuff with u
   return u
endfunction

function a takes nothing returns nothing
   local unit u = null

   call b(u)
   //  do stuff with u
   set u = null
endfunction

This works since you don't have to null variables passed to other functions, you only have to null handle locals in the function that defined them.

Hope that helps :thup:

 

[Arkan]

Alright, I know what do to now. Thanks for your input.