Re: Testing m68k changes on AmigaOS and Linux/m68k

[Gunther Nikl <gni at gecko dot de>]

On Thu, Oct 23, 2003 at 07:42:24PM +0200, Bernardo Innocenti wrote:
> Gunther Nikl wrote:
> >  The approach with the array is nasty :-/ Every usage of such macro
> >  will create a distinc array and this will eat up stackspace. Thats
> >  why I always disabled these macros.
> 
> I don't quite understand.  There's (almost) no difference in stack
                                      ^^^^^^
  Thats the import difference.

> space usage between this:
> 
>  {
>     int v[] = { 1, 2, 3, 4, 5 };
>     extern foo(int *);
>     foo(v);
>  }
> 
> ...and this:
> 
>  {
>     extern foo(...);
>     foo(1, 2, 3, 4, 5);
>  }
> 
> With the varargs form, the compiler will push all arguments on the
> stack before calling foo(), effectively wasting the same amount of
> stack space of the local array.

  The array is allocated at _frame generation_. Now imagine using a lot
  of such calls where every array is only used _one_ time. The varargs
  form uses the stackspace only temorary when making the call and cleans
  up soon after the call returns.

> When I had to pass a taglist made entirely of constant values, I used to
> do this instead:
> 
>   {
>      static const int tags[] = {...};
>      ...
>   }

  This is of course much better since the array is created a compile time
  and placed in readonly-memory.

  Gunther