printf '#include "SYS.h"\nWSYSCALL(write,_sys_write)\nWEAK_ALIAS(_write,_sys_write)\n' >write.S

WSYSYCALL becomes:

VALUE   VAR
write = weak
_sys_write = strong

PSEUDO(weak,weak)

write = x
write = y

_SYSCALL(x,y);
[code for syscall]
ret


_SYSCALL(x,y)

.text ; _ALIGN_TEXT /* really .align 4 */

2: PIC_PROLOGUE;  


	/* #define PIC_PROLOGUE    \
        	pushl   %ebx;   \
        	call    1f;     \
	1:                      \
        popl    %ebx;   \
        addl    $_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx

movl PIC_GOT(CERROR), %ecx
	#define PIC_GOT(x)      

PIC_EPILOGUE;

	#define PIC_EPILOGUE    \
        	popl    %ebx

jmp *%ecx;

_SYSCALL_NOERROR(x,y)

write = x
write = y

_SYSCALL_NOERROR(x,y)

ENTRY(x);
SYSTRAP(y);

	#define _ENTRY(x) \
        .text; _ALIGN_TEXT; .globl x; .type x,@function; x:

	#define SYSTRAP(x)      movl $(SYS_ ## x),%eax; int $0x80

jc 2b

So, with that heap of code I suppose we must do something like:

 mywrite:
  .text
  .align 4
2:
  pushl %ebx
  call 1f;
 
  1:
  popl %ebx
  addl $_GLOBAL_OFFSET_TABLE_+[.-1b],%ebx
  movl __cerror,%ecx 
  popl %ebx
  
  .text 
  .align 4
  movl $4,%eax
  int $0x80

  jc 2b

 cerror: 

----
function f {int a ; int b} {
 return [+ $a $b]
}

function main {int argc} {
 int r

 set r [f 1 2]

 return 0
}

-----
comp:function creates 
 f:
Now we eval {int a ; int b} (after split'ing)

Now we set the locals:
 movl (%esi),%eax
 movl %eax,[get.symbol.offset a] (substituted at compile time)
 addl $4,%esi

 movl (%esi),%eax
 movl %eax,[get.symbol.offset b]  
 addl $4,%esi

Now eval the body.

return places its result in %eax

This all means that we need to handle main specially, or have our own start.