unit u inst stored in function b right?

[Pinzu]

function b takes unit u returns nothing 

endfunction

function a takes nothing returns nothing
     local unit u = GetTriggerUnit()
     call b(u)
     set u = null
endfunction

 

[Flux]

Can you rephrase your question? What do you mean "inst"?

I don't see problem with the code but using

local unit u2 = GetTriggerUnit()
call b(u2)
set u2 = null

will also work if that is what's bothering you

 

[Wietlol]

There are 2 different unit u.
In function a, there is unit u, which points to GetTriggerUnit().
That pointer is sent to function b.
In function b, there is another unit u, which points to the same GetTriggerUnit().

So if you mean, are they both the same unit? then yes.
If you mean, are they the same variable? then no.
If you do this, you still displays the name twice:

function b takes unit u returns nothing
    call BJDebugMsg("unit name = " + GetUnitName(u))
    set u = null
endfunction

function a takes nothing returns nothing
    local unit u = GetTriggerUnit()
    
    call b(u)
    
    call BJDebugMsg("unit name = " + GetUnitName(u))
    
    set u = null
endfunction

EDIT:
On the other hand...
this is function b:

function b
    local unit u = GetParameter(1)
    
    
    (set u = null)
endfunction

So yea you can use unit u, but it is a local varaible of function b.
the difference is that it is a parameter and parameters are automatically nulled at end. (that is something of JASS compiler)