Re: [Qemu-devel] [PATCH] Fix char signedness

[Martin Guy]

> gcc on ARM systems default to unsigned.  The C standard specifically
> states that char is either signed or unsigned at the whim of the
> implementor

Or, more to the point, at the behest of the machine architecture.
Having to generate code to sign-extend the hard way every time you do
char-integer promotion if the hardware doesn't do it automatically
would be long and inefficient, specially since it happens all the
time.
This has been a problem since the "All the world's a VAX" days, the
classic boob being

char c;
while ((c = getchar()) != EOF) {
    ...
}

of course, 255 always != -1 so it loops forever.
Check how many of your C primers get this wrong!
The flipside of that boob is that on a signed char architecture, the
loop will exit prematurely when it meets a 255 character.

These days instead, all the world's a 386 and anything different is broken...

24-bit integers, anyone? :)

  M