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Returning values from ASM functions
Post by David Williams on Jul 17th, 2010, 7:56pm

I'm a bit embarrassed to have to ask, but...

I quite often - nearly always, in fact - push all registers onto the stack at the beginning of a routine:

Code:
.routine
pushad ; preserve registers

(do stuff)

popad ; restore registers
ret


But I find that when I need to return a value in EAX, I do this:

Code:
.routine
pushad
(do some stuff...)
(put some value in EAX)
mov [^temp], eax
popad
mov eax, [^temp]
ret



Is there a neater way to return a value in EAX without stashing the return value in a temporary memory location first?


Thanks.


David.
Re: Returning values from ASM functions
Post by admin on Jul 17th, 2010, 9:53pm

on Jul 17th, 2010, 7:56pm, David Williams wrote:
Is there a neater way to return a value in EAX without stashing the return value in a temporary memory location first?

I don't know whether you would consider it 'neater', but this is the code I invariably use:

Code:
      mov [esp+28],eax
      popad
      ret

Richard.
Re: Returning values from ASM functions
Post by David Williams on Jul 18th, 2010, 7:36pm

on Jul 17th, 2010, 9:53pm, Richard Russell wrote:
I don't know whether you would consider it 'neater', but this is the code I invariably use:

Code:
      mov [esp+28],eax
      popad
      ret

Richard.


Thank you!


David.