import std.stdio;

void main()
{
	char[][] tmp;
	
	tmp ~= "1";
	tmp ~= "2";
	//add these, no problem
	//tmp ~= "3";
	//tmp ~= "4";
	//tmp ~= "5";
	
	for(int i = 0; i < tmp.length-3; i += 3)
	{
		writefln(tmp[i],",",tmp[i+1],",",tmp[i+2]);
	}
}

The code above causes an array bounds error. This occurs because tmp.length-3 == 4294967295 instead of -1.
There are no errors or warnings about comparing an int 'i' with a uint 'tmp.length'.

Regan

Regan Heath wrote:
> import std.stdio;
> 
> void main()
> {
>     char[][] tmp;
>         tmp ~= "1";
>     tmp ~= "2";
>     //add these, no problem
>     //tmp ~= "3";
>     //tmp ~= "4";
>     //tmp ~= "5";
>         for(int i = 0; i < tmp.length-3; i += 3)
>     {
>         writefln(tmp[i],",",tmp[i+1],",",tmp[i+2]);
>     }
> }
> 
> The code above causes an array bounds error. This occurs because  tmp.length-3 == 4294967295 instead of -1.
> There are no errors or warnings about comparing an int 'i' with a uint  'tmp.length'.
> 
> Regan

The problem never occured to me because I usually write like this:

for(int i = 0; i+3 < tmp.length; i += 3)

On Wed, 17 Aug 2005 20:40:23 +0800, zwang <nehzgnaw@gmail.com> wrote:
> Regan Heath wrote:
>> import std.stdio;
>>  void main()
>> {
>>     char[][] tmp;
>>         tmp ~= "1";
>>     tmp ~= "2";
>>     //add these, no problem
>>     //tmp ~= "3";
>>     //tmp ~= "4";
>>     //tmp ~= "5";
>>         for(int i = 0; i < tmp.length-3; i += 3)
>>     {
>>         writefln(tmp[i],",",tmp[i+1],",",tmp[i+2]);
>>     }
>> }
>>  The code above causes an array bounds error. This occurs because  tmp.length-3 == 4294967295 instead of -1.
>> There are no errors or warnings about comparing an int 'i' with a uint  'tmp.length'.
>>  Regan
>
> The problem never occured to me because I usually write like this:
>
> for(int i = 0; i+3 < tmp.length; i += 3)

Thanks. I'll probably change it to something like that.. I had recoded it to:

int len = tmp.length;
for(int i = 0; i < len-3; i += 3)

Regan

These kinds of problems cannot be solved by juggling around the promotion rules, conversion rules, etc. They just shift and manifest themselves in some other way. The only way to deal with it is to be wary of code that might cross 0 or int.max boundaries.

On Sat, 27 Aug 2005 14:33:57 -0700, Walter <newshound@digitalmars.com> wrote:
> These kinds of problems cannot be solved by juggling around the promotion
> rules, conversion rules, etc. They just shift and manifest themselves in
> some other way. The only way to deal with it is to be wary of code that
> might cross 0 or int.max boundaries.

There appears to be no warning (when using -w) when comparing signed and unsigned, eg.

void main()
{
	uint i = 4;
	int j = 6;	
	if (i < j) {}
}

C:\Library\D\src\temp>dmd -w signed.d
C:\Library\D\dmd\bin\..\..\dm\bin\link.exe signed,,,user32+kernel32/noi;

Perhaps you could add one?

Regan