------- Comment #2 from joseph at codesourcery dot com 2008-11-07 12:46 -------
Subject: Re: New: 'warning: comparison between signed and
unsigned' shouldn't be given for equality comparisons
On Fri, 7 Nov 2008, edwintorok at gmail dot com wrote:
> Consider this code:
>
> int foo(int a, unsigned b)
> {
> return a != b;
> }
> $ gcc -O2 -Wall -W foo.c -c
> foo.c: In function foo:
> foo.c:3: warning: comparison between signed and unsigned integer expressions
Seems correct to me. You could have a == -1 and b == UINT_MAX and they
would compare equal, but it's not at all obvious from the code that this
is the user's intent; and if it is their intent, they can use an explicit
cast.
> FWIW, if I change int to 'short int' or 'signed char' (and unsigned
> appropriately) I get no warning.
Both short and unsigned short will be promoted to int before the
comparison, so you won't get -1 and USHRT_MAX comparing equal.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38046
