Strange Error. . .

**Kennedy** · 08-14-2009

Code:

char fgetbyte(FILE *file)
{
        short retval;
        char num;

        num = ahextoc(fgetc(file));
        if (num < 0){
                return num;
        }
        retval = num;
        retval <<= 4;
        num = ahextoc(fgetc(file));
        if (num < 0){
                return num;
        }
        retval |= num;
        return retval;
}

The bolded above would be line 58.

Originally Posted by gcc

reprogram.c:58: warning: comparison is always false due to limited range of data type

How am I getting this warning? I don't get it. This _IS_ a char not an unsigned char. . .

**cas** · 08-14-2009

char can be either signed or unsigned. Apparently on your system it is unsigned. Perhaps your ahextoc() function should act like fgetc() and return an int so it can return a negative value on error and a positive value otherwise. Since you're passing the result of fgetc() into the function that should be pretty easy to manage.

**Salem** · 08-14-2009

Try with the appropriate flags

Originally Posted by gcc manual

-funsigned-char
Let the type char be unsigned, like unsigned char.

Each kind of machine has a default for what char should be. It is either like unsigned char by default or like signed char by default.

Ideally, a portable program should always use signed char or unsigned char when it depends on the signedness of an object. But many programs have been written to use plain char and expect it to be signed, or expect it to be unsigned, depending on the machines they were written for. This option, and its inverse, let you make such a program work with the opposite default.

The type char is always a distinct type from each of signed char or unsigned char, even though its behavior is always just like one of those two.
-fsigned-char
Let the type char be signed, like signed char.

Note that this is equivalent to -fno-unsigned-char, which is the negative form of -funsigned-char. Likewise, the option -fno-signed-char is equivalent to -funsigned-char.

An unqualified char can be signed or unsigned.

**Kennedy** · 08-14-2009

Well now that is REALLY annoying. I have two cross compilers for this system. One (gcc 4.2.2) defaults to anything unspecified is signed. This one (gcc 3.2.2) is backwards.

What a completely freaky compiler. . .

Thanks Salem!

**Sebastiani** · 08-14-2009

AFAIK, it really isn't necessary to pass around anything smaller than an int, since the compiler will just widen it anyway (at least that's how it I've seen it done).

**Kennedy** · 08-14-2009

I'm reading an S record file. Each nibble is specified in the file, then I convert that to either the LSB or MSB of a short array. When making assignments to this array, I didn't want the compiler squawking at me for type conversions. <-- I don't know that it would, but that used to be the case with gcc.

**Sebastiani** · 08-14-2009

Originally Posted by Kennedy

I'm reading an S record file. Each nibble is specified in the file, then I convert that to either the LSB or MSB of a short array. When making assignments to this array, I didn't want the compiler squawking at me for type conversions. <-- I don't know that it would, but that used to be the case with gcc.

Well, it should for the very fact that Cas pointed out: the standard doesn't specify whether or not a char is to be signed or unsigned (unfortunately!), and so the code is actually undefined behaviour, and isn't guaranteed to work on all systems.

Thread: Strange Error. . .

Thread Tools

Search Thread

Display

Strange Error. . .

Similar Threads

An error is driving me nuts!

more then 100errors in header

Dikumud

ras.h errors

Learning OpenGL