Re: [cc65] Problem with code compiled as overlay.

From: "Payton Byrd" ; on Saturday, January 21, 2012; at 01:33 PM -0500
>
> I've got a very strange problem.  I have a project that Oliver has helped
> me with to build an overlay example so I can start a bigger project.
>
> The problem I've run into is that the code compiled for the overlay has a
> very serious defect in it.  My overlay is compiling to $C000, and the C
> looks like this:
>
> #include <stdlib.h>
> #include <stdio.h>
> #include <fcntl.h>
> #include <unistd.h>
>
> #pragma code-name (push, "OVL1CODE");
>
> int overlay1()
> {
> printf("This is overlay 1.");
> return 1;
> }
>
> #pragma code-name (pop);
>
> Now, the disassembled code generated by cc65 looks like this:
>
> ** Monitor 012 002
> (C:$e5d1) d c000
> .C:c000   A2 14      LDX #$14
> .C:c002   20 8D 0B   JSR $0B8D
> .C:c005   A0 02      LDY #$02
> .C:c007   20 68 12   JSR $1268
> .C:c00a   A2 00      LDX #$00
> .C:c00c   A9 01      LDA #$01
> *.C:c00e   4C 13 C0   JMP $C013*
> .C:c011   60         RTS
> .C:c012   00         BRK
> .C:c013   00         BRK
> .C:c014   00         BRK
> .C:c015   00         BRK
> .C:c016   00         BRK
> .C:c017   00         BRK
> .C:c018   00         BRK
> .C:c019   00         BRK
> .C:c01a   00         BRK
> .C:c01b   00         BRK
> .C:c01c   00         BRK
> .C:c01d   00         BRK
> .C:c01e   00         BRK
> .C:c01f   00         BRK
> .C:c020   00         BRK
> .C:c021   00         BRK
> .C:c022   00         BRK
> .C:c023   00         BRK
> .C:c024   00         BRK
> .C:c025   00         BRK
> .C:c026   00         BRK
> .C:c027   00         BRK
> .C:c028   00         BRK
> (C:$c029)
>
> Please note the code at $C00E.  It jumps into a BRK statement at $C013.
> This makes no sense to me, and appears to be some kind of bug or side-
> effect.

You loaded it wrong.  You forgot that the overlays don't have load
addresses.  Therefore, when you loaded it as a program, it lost
its first two bytes.  $C013 actually is the location of the "rts".

>
> PS.  Another issue I have with this code is that the string literal in the
> method is not compiled as part of the overlay.  I may have a lot of text in
> each overlay, how do I make sure all the literals are compiled in the
> overlays?

You must use the "rodata-name" pragma.  If you put your overlays in the
same C source file as your main code, then you need to use the pragma
"local-strings", as well.

P.S., If every overlay is written in its own source file, then you don't
need to pop their pragmas.

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