__inline and change of sign warning

Hi all,

I would like to discover why the compiler issues warning #68 (integer conversion resulted in a change of sign) for the code below. It is issued only for -O3, "Optimize for Time" enabled and when the function is inlined (__inline keyword).

I have tried to cast anything which could be implicitly converted to int back to uint, but no chance to get rid of this warning.

armcc.exe V4.0.0.524

static __inline uint8_t IsDecDigit(char c)
{
    return (   (c >= '0')
            && (c <= '9'));
}

...

static void UseIt(void)
{
    char *name;
    ...
    /* Initialize the name to something useful */
    ...
    if (   (IsDecDigit(name[3])) /* <- warning issued for this expression */
        && (IsDecDigit(name[4]))
        && (IsDecDigit(name[5]))
        && (IsDecDigit(name[6]))
    {
        ...
    }
}

Thanks for responses.

Regards Pavel