Re: [cc65] Referencing 'Split' Labels

On Tue, Mar 16, 2004 at 09:09:32AM +1030, Todd Elliott wrote:
> The following code did not compile correctly under ca65?
>
> 	LoadW r0, epsLineBuf+14	; point to start of coordinates.
>
> The LoadW is a macro, meaning that r0 ($02-$03) will contain the address
> of epsLineBuf+14.
>
> Problem is, the high byte seems to be wrong; It appears that the +14 is
> added to high byte, a no-no.

ca65 is correct, the macro is not.

As you can see from the operator precedence table in the ca65 docs, the '<'
and '>' operators have a higher precedence than the '+' operator. This means
that

        lda     #<epsLineBuf+14

will *first* take the low byte of the label, and *then* add 14 to the result.

When using the '<' and '>' operators, the operand must usually be put into
parenthesis:

        lda     #<(epsLineBuf+14)

You can also use the new pseudo functions .lobyte and .hibyte. Since they are
functions, braces are always needed, which means that you cannot forget
them:-)

        lda     #.lobyte(epsLineBuf+14)

Maciej, can you have a look at the GEOS macros? Todd didn't tell where he got
the LoadW macro from, but the one in libsrc/geos/geosmac.ca65.inc does
definitely have this problem.

Regards


        Uz


-- 
Ullrich von Bassewitz                                  uz@musoftware.de
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