Re: macro behavior

[Erik Christiansen <erik at dd dot nec dot com dot au>]

On Thu, Apr 14, 2005 at 04:42:59PM +0200, Jan Beulich wrote:
> (1) If I want to append a constant suffix to the expanded string, I
> see no way to do so in default mode; in .altmacro mode I am able to do
> so using the & macro operator:
>
> 	.macro m sym
> 	.equiv &sym&_, 1
> 	.endm

   For me, prepending of constants, and appending of the constant '.' and
parameter names works fine in gas. (Tested only on avr-as 20030512, so far,
I'm afraid). For some odd reason, your choice of '_' does break the
appending mechanism. Here is what works for me:

   .macro struct_elem name, size, elem    ; Declare an element of struct "name"
   \name.\elem = oneof_\name              ; Generate element offset.
   oneof_\name = oneof_\name + \size      ; Size of one struct.
   .endm

   The following expands happily:

   .section .data,"aw"
   struct fruit
   struct_elem fruit,1,apple
   struct_elem fruit,3,orange
   struct_elem fruit,1,banana
   end_struct fruit,4            ; Array of 4 structs.

to:

  60                    .section .data,"aw"
  61                    struct fruit
  61                 > oneof_fruit =0
  62                    struct_elem fruit,1,apple              
  62                 > fruit.apple =oneof_fruit                
  62                 > oneof_fruit =oneof_fruit+1              
  63                    struct_elem fruit,3,orange
  63                 > fruit.orange =oneof_fruit
  63                 > oneof_fruit =oneof_fruit+3
  64                    struct_elem fruit,1,banana
  64                 > fruit.banana =oneof_fruit
  64                 > oneof_fruit =oneof_fruit+1
  65                    end_struct fruit,4         ; Array of 4 structs.
  65                 > sizeof_fruit =oneof_fruit*4
  65                 > numof_fruit =4
  65                 > fruit:.space sizeof_fruit
  65 0000 0000 0000  > .space sizeof_fruit
  65      0000 0000

allowing stuff like:

   ldd   r16,Y + fruit.banana   ; r16 = fruit[3].banana

   And, yep, it's '_' that is your bugbear with .equiv syntax also,
'cos this works too:

  64                    struct_elem fruit,1,banana 
  64                 > .equiv fruit.banana,oneof_fruit


   If a more flexible syntax evolves, that would be nifty, but the
existing code is in volume production, so is fixing what we have an
option?  ;-)

Erik