Re: [avr-gcc-list] avr-as: .byte SYMA - SYMB?

[Dmitry K.]

Using
        .byte  SYMA-SYMB
        .align 1
work OK with binutils-030428 .
Perhaps, problem was: odd address after .byte .

Best wishes.

27 May 2003 20:19 Joerg Wunsch:
> (I figure avr-as is not fully on-topic, but since the developers of
> avr-gcc and avr-as are identical, i'd rather post that here than on
> avr-chat.)
>
> I tried to define a byte in avr-as to the difference of two
> (relocatable) symbols.  I pulled my hair out, but failed so far.
>
> So something like:
>
> .text
> SYMA: mov     rthis, rthat
> SYMB: ldi     rthat, 42
> ...
>       .byte   SYMA-SYMB
>
> This should be possible, since the difference of two relocatable
> symbols is an absolute value by itself.  It's even an absolute value
> that can be computed by the assembler in that case (as opposed to one
> that is only known at link time).
>
> I always get an "illegal relocation size: 1" message.
> Just-shoot-around-without-knowing-what-i'm-doing attempts to use lo8()
> or pm() only add "garbage at end of line" messages to this.
>
> Using
>
>       .word   SYMA-SYMB
>
> however does work (and yields the expected result).
>
> I see that message comes from avr_cons_fix_new() in
> gas/config/tc-avr.c, but the constraints of what could be handled in
> this function are unintelligible to me at the first glance.