Ok, thanks for your answer !!!
I was warned about that stuff because I saw a program that compared some char value to special cgaracters, '' for example that was used as a string modifier... I'll don't tell you that it didn't work on gumstix without -fsignedchar ...(heu I told it ...)
 
2005/8/4, Dave Hylands <dhylands@gmail.com>:
Hi Jerome,

>  I saw a bug while building a fresh root_fs :
>
>  In file included from regex.c:646:
>  regex.c: In function `byte_regex_compile':
>  regex.c:3291: warning: comparison is always true due to limited range of
> data type

It probably isn't a bug, just paranoia (althougth I'm hesitant to say
that because it starts to get into "religious" areas about coding).

Personally, I like all of my code to compiler with no errors - no warnings.

Anyways, and example of where this could easily occur is something like:

char x = SomeFunc();

if (( x < 0 ) || ( x > 3 ))
{
    ...do something since x is out of range...
}

On machines where x is signed the condition is OK. On machines where x
is unsigned, the x < 0 part  will always fails, since x is always
positive.

So, don't sweat the warnings, there are LOTS of them. For the most
part, if it compiles and links, then its OK (at least that's my
experience).

I looked at the particular example, which I think is from building
uClibc and the code is:

if (c1 < CHAR_CLASS_MAX_LENGTH)

where c1 is an unsigned char, and CHAR_CLASS_MAX_LENGTH is 256. So the
condition, on this particular machine with this particular
configuration winds up with a redundant test.

Because regex.c is VERY portable, on many other machines in many other
environments this is a very legitimate test.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/


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--
Jerome