char[] annoyance...

S. Chancellor dnewsgr at mephit.kicks-ass.org
Mon Apr 10 00:50:24 PDT 2006


On 2006-04-09 17:23:06 -0700, "Regan Heath" <regan at netwin.co.nz> said:

> Take this code:
> 
> void main()
> {
> 	//..open a file, read line for line, on each line:
> 
> 	for(int i = 0; i < line.length-2; i++) {
> 		if (line[i..i+2] != "||") continue;
> 		//..etc..
> 	}
> }
> 
> 
> There is a subtle bug. On all lines with a length of 0 or 1 it will 
> give  the following error:
> 
> Error: ArrayBoundsError line_length.d(6)
> 
> 
> The problem is of course the statement "i < line.length-2". line.length 
> is  unsigned, and when you - 2 from an unsigned value.. well lets just 
> say  that it's bigger than the actual length of the line - 2.
> 
> 
> Of course there are plently of other ways to code this, perhaps using  
> foreach, but that's not the point. The point is that this code  _can_ 
> be  written and on the surface looks fine. Not even -w (warnings) spots 
> the  signed/unsigned problem. At the very least can we get a warning 
> for this?
> 
> Regan


if( line[i.. (i+2 > $ ? $ : i +2 ) ] != "||")
{
	...
}

Is that not allowed in the [..] syntax?

-S.




More information about the Digitalmars-d mailing list