[Qemu-trivial] C99 loop vars? [was: gtk: Fix compiler warnings with -Werror=sign-compare]

[Michael Tokarev]

05.11.2013 00:38, Laszlo Ersek wrote:
> On 11/04/13 21:07, Peter Maydell wrote:
> > On 4 November 2013 19:51, Stefan Weil <address@hidden> wrote:
> > > With -Werror=sign-compare (not enabled by default), gcc shows these errors:
> > >
> > > ui/gtk.c: In function ‘gtk_release_modifiers’:
> > > ui/gtk.c:288:19: error:
> > >   comparison between signed and unsigned integer expressions 
> > > [-Werror=sign-compare]
> > > ui/gtk.c: In function ‘gd_key_event’:
> > > ui/gtk.c:746:19: error:
> > >   comparison between signed and unsigned integer expressions 
> > > [-Werror=sign-compare]
> >
> > If this warning is going to complain about entirely
> > safe and idiomatic code like
> >
> >     int i;
> >     static const int some_array[] = {
> >         0x2a, 0x36, 0x1d, 0x9d, 0x38, 0xb8, 0xdb, 0xdd,
> >     };
> >
> >     for (i = 0; i < ARRAY_SIZE(some_array); i++) {
> >         ...
> >     }
>
> (Entirely safe, and completely non-idiomatic: "i" should be size_t, as
> that is the type of the sizeof operator's result.)

Maybe in some places we should switch to C99 which allows to declare
a loop variable inside the loop header, like this:

  for(int i = 0; i < ARRAY_SIZE(..); i++) {
  }

?

This is much better than a per-unit (function-level) declaration because
by changing type in one place we don't change it for other places which
might become wrong in the result...

But this requires compiling whole thing with gcc -std=c99, which might
bit problematic.

But as it is, the original patch from Stefan, -- I don't think it's a
good idea to apply it.  The code is obviously correct, ARRAY_SIZE is
a fixed value, the compiler is able to determine this and shut pretty
much up ;)

Thanks,

/mjt