RE: Qwery regarding the While() in gcc (GCC) 3.2.2 20030222 (Red Hat Linux 3.2.2-5)

[lrtaylor at micron dot com]

So, which one is not working the way you expected?  Both of these are
inherently flawed, since neither variable can ever go negative.  In the
first case, the unsigned short gets promoted to an int for the
comparison, so it will always be greater than -1 (since 0x0 wraps back
around to 0xffff, which is 2^16-1 rather than -1).  In the second case,
it looks like the -1 is getting promoted to an unsigned int which will
end up being 2^32-1 (since a -1 is 0xffffffff), which is definitely
greater than 3.

Basically, if you want to compare to -1, you need to use signed index
variables.

Cheers,
Lyle

-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On
Behalf Of Riyash M H
Sent: Wednesday, February 25, 2004 12:13 AM
To: gnu@gnu.org
Cc: gcc-help@gcc.gnu.org
Subject: Qwery regarding the While() in gcc (GCC) 3.2.2 20030222 (Red
Hat Linux 3.2.2-5)

Hai pal,

I am using gcc (GCC) 3.2.2 20030222 (Red Hat Linux 3.2.2-5). I have got
a code which is not
working according to what i expect. Can u tell me the reason behind that
or is that a bug in the
gcc version, i dont have another complier, i executed it with its "g++ "
clone also. That too gave
me the same results,

-----------------------------------------

int main(){
        unsigned short i = 3;
        while(i > -1)
                printf("%u\n",i--);
        return 0;
}

output: 3,2,1,0,65535,...............
------------------------------------------- 

int main(){
        unsigned int i = 3;
        while(i > -1)
                printf("%u\n",i--);
         return 0;
}

output: "Nothing"
--------------------------------------------

One using integer, the compiler is not producing even the assembly code
for the while part.

The only difference is that in the first the 'i' is 'short' and in the
second it is 'int'.

please take a look to help me........

thanks..

=====
Riyashmon H

Software Engineer,
Qcomp Systems & Softwares
#2 1st Floor, Vivek Complex,
SM Road, Jalahalli West,
Bangalore - 560015

Ph: 28399948
Email: riyash@qcomp.cc

________________________________________________________________________
Yahoo! India Insurance Special: Be informed on the best policies,
services, tools and more. 
Go to: http://in.insurance.yahoo.com/licspecial/index.html