Hmmm... that works.  Some other interesting points to note...

Original, which failed...
	if (S2 >=3D (S2_MAX + S2_STEP))
		S2 =3D S2_MIN;
This disassembled to...
   0B16    0E82     MOVLW 0x82
   0B18    5DBF     SUBWF 0xbf, W, BANKED
   0B1A    0EFF     MOVLW 0xff
   0B1C    59C0     SUBWFB 0xc0, W, BANKED
   0B1E    E303     BNC 0xb26	'
	...



With the type-casting done in the definition as you suggested, the =20
same statement disassembles to...
   0B30    0E82     MOVLW 0x82
   0B32    5DBF     SUBWF 0xbf, W, BANKED
   0B34    0E00     MOVLW 0
   0B36    59C0     SUBWFB 0xc0, W, BANKED
   0B38    E303     BNC 0xb40
	...

Here, the calculation of 125+5 is still correct (130 =3D 0x82), but the =20
3rd instruction is different.

I can see now what it's thinking here, that 125 will fit in a signed =20
byte, so it uses that.  And if I change the statement to "if (S2 >=3D =20
130)", then it knows that a signed byte won't work, so it interprets =20
it as unsigned, and works correctly.  But this is so not intuitive.  =20
When the compiler does the math on the defines and comes up with 130, =20
it should know then that a signed byte won't work.

I'm going to reserve space on this list now for a future rant on this, =20
when this bites me in a big way.  I just know that's coming.

Thanks,
-Neil.




Quoting Tamas Rudnai <tamas.rudnai@gmail.com>:

> Have you tried with a modification like this:
>
> #define S2_MIN  ( (unsigned) 90 )
> #define S2_MAX  ( (unsigned) 125 )
> #define S2_STEP  ( (unsigned) 5 )
>
> Tamas
>
>
> On 25 January 2012 01:09, PICdude <picdude3@narwani.org> wrote:
>
>> Quoting Mark Rages <markrages@gmail.com>:
>>
>> > On Tue, Jan 24, 2012 at 4:27 PM, PICdude <picdude3@narwani.org> wrote:
>> >> Hmmm... still tinkering with C18 and ran into this oddity...
>> >> ...
>>
>> >
>> > How is "S2" declared?  If it is an int8_t (aka char) then 125+5 =3D
>> > -126, which is always going to be less than S2_MIN, so S2 will remain
>> > at 90.
>> >
>>
>> "unsigned int", because the full range of values will be 0 to 350.
>>
>>
>>
>>
>> --
>> http://www.piclist.com PIC/SX FAQ & list archive
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>>
>
>
>
> --
> int main() { char *a,*s,*q; printf(s=3D"int main() { char *a,*s,*q;
> printf(s=3D%s%s%s, q=3D%s%s%s%s,s,q,q,a=3D%s%s%s%s,q,q,q,a,a,q); }",
> q=3D"\"",s,q,q,a=3D"\\",q,q,q,a,a,q); }
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>



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