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

[Bill K. <nb...@so...>]

On Wed, Mar 03, 2021 at 07:06:10PM -0800, sje...@sh... wrote:
> Hi Bill,
> 
> Calling any C library functions in interrupts is likely not going to work
> out well, at least that used to be the case with cc65.  You pretty much have
> to write these in assembly, or be very very careful about what C code you
> use and probably look at what it's doing, and whether or not your interrupt
> is going to stomp all over other things.  

Yeah, it wasn't until I looked at the assembler output (.s file) of cc65
that I realized things like:

  togl = togl + 1;
  if (togl == 4) {
    ...
  }

were causing a bunch of JSRs.  I'm still new at this. :)

-bill!