Re: [avr-gcc-list] integer overflow

[eric]

> Ömer,
> 
> > i have an overflow warning from the compiler
> > here is the code that makes the problem
> > unsigned long val;
> > 
> > val = 1000*60*60*24;
> > 
> > i think the problem stems from the sizeof long , as far 
as i know long
> > is 4 bytes for atmel processors and integer is 2 
bytes.the maximum
> > value for 4 bytes is
> > 
> > FFFFFFFF which is 4,294,967,295 that is bigger than 
86,400,000.
> > 
> > if long is 2 bytes than is there a built in structure 
for carrying 4
> > bytes ?
> 
> Try...
> 
>   val = 1000L*60*60*24;
> 
> "Ints" are 2 bytes with "avr-gcc".  Integer constant 
expressions
therefor> e
> use only 2 bytes, unless you somehow promote the 
expression evaluation to
> use 4-byte longs.  Replacing 1000 by 1000L will cause 
this to happen. 
> 
> Best regards,
> 
> Bruce
> 
> P.S.- There are many other ways to do this, which I'm 
sure Joerg will
soo> n
> share with you...

Yeah? You're only half right.

If you read Ömer's post, val is an unsigned long.

So you need to do:

val = 1000UL*60*60*24;

to make it an unsigned long constant to match the type of 
the variable.

Eric