Re: [cc65] Strange behaviour of a simple code

Could it be because inc_test overwrites a and x registers + flags?

Not sure why that would give such a behavior, but... it is the first thing
that strikes me.

Johan

On Mon, Aug 9, 2010 at 10:51 AM, Carlos <shangri-la@teleline.es> wrote:

>  In these last days i'm really puzzled with a strange behaviour with a
> cc65 simple program, don't know if is some kind of bug or a bad code from my
> part but can't find where the problem can be.
>
> The result of the main code is not right:
>
> 1.  FROM:  17600
> 1.  TO:  30719
> 3.  FROM:  17473
> 3.  TO:  30209
>
> but if uncomment the two commented printf lines then the result is the
> expected:
>
> 1.  FROM:  17600
> 1.  TO:  30719
> 2.  FROM:  17600
> 2.  TO:  30336
> 3.  FROM:  17728
> 3.  TO:  30464
>
>
> why is the behaviour changed only for the printf lines? Any ideas?
>
>
> test.c
> ------
>
> #include <stdio.h>
>
> void inc_test(void);
>
> unsigned int from, to;
>
>
> // MAIN
> void main(void)
> {
>  from = 17600;
>  to = 30719;
>
>  printf("1. FROM: %u\n", from);
>  printf("1. TO: %u\n", to);
>
>  if (to >= 0x7740)   // 30528
>  {
>   to = 0x7680;  // 30336
>  }
>  else
>  {
>   to = 0x7740;
>  }
>
>  //printf("2. FROM: %u\n", from);
>  //printf("2. TO: %u\n", to);
>
>  inc_test();
>  ++from;
>  ++to;
>
>  inc_test();
>  ++from;
>  ++to;
>
>  printf("3. FROM: %u\n", from);
>  printf("3. TO: %u\n", to);
> }
>
>
>
> inctest.s
> ---------
>
> .export _inc_test
>
> .import _from
> .import _to
>
>
> .CODE
>
> ; ---------------------------------------------------------------
> ; _inc_test
> ; ---------------------------------------------------------------
> _inc_test:
>
>  ldx #$15
>
> @LGO:
>
>  lda _from
>  adc #$03
>  sta _from
>  lda _to
>  adc #$03
>  sta _to
>
>  dex
>  bne @LGO
>
>  rts
>
>
>
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