Re: [cc65-devel] c64 - getting seemingly random chars on screen

[Mike F. <mik...@pr...>]

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, March 2, 2021 7:16 PM, Michael Parson <mp...@bl...> wrote:

> On 2021-03-02 17:44, Michael Parson wrote:
>
> > On Tue, 2 Mar 2021, gr...@gm... wrote:
> >
> > > I'd use watchpoints on the entire screen, like
> > > . watch store 0400 07e7
> > > . x
> > > (assuming your screen memory is at 0400)
> > > then when the first wrong character pops up break into the monitor
> > > again, and you'll see a list of writes to the screen. find out which
> > > one wrote the wrong character, and you know where it happens.
> >
> > Thanks, I'll give that a shot.
>
> Took a few tries, but here's where it happens:
>
> #1 (Stop on store 057c) 006 020
> .C:222d 91 D1 STA ($D1),Y - A:4A X:09 Y:14 SP:ee ..-....C
> 84639134
> .C:222f AD 86 02 LDA $0286 - A:4A X:09 Y:14 SP:ee ..-....C
> 84639134
>
> Right when the piece I clicked on turned red, I also got a red 'I'
>
> 222d is in the middle of the subroutine starting at 2229:
>
> .C:2229 05 C7 ORA $C7
> .C:222b A4 D3 LDY $D3
> .C:222d 91 D1 STA ($D1),Y
> .C:222f AD 86 02 LDA $0286
> .C:2232 91 F3 STA ($F3),Y
> .C:2234 60 RTS
>
> Which, according to the generated label file, is '.putchar'
>
> There should only be 1 character being put to the screen at that time,
> the red version of whatever character I clicked on, which is happening,
> just that the extra & erroneous character shows up too.
>
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Michael Parson
> Pflugerville, TX
>
> cc6...@li...
> https://lists.sourceforge.net/lists/listinfo/cc65-devel

I recently ran into a similar issue with the VIC-20; not sure if this issue is resolved (sounds like you got it) but for me what did it was a combination of using a different config file and not using "static" in a string I was using; it sounds like yours is with putchar, so this may be totally irrelevant, but I just thought I'd throw it out there anyway, in case it helps.  I'm a big fan of conio.h, but I think my problem was just a lack of memory (stuff was getting overwritten).  HTH