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

[Michael Tokarev <mjt@tls.msk.ru>]

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 <sw@weilnetz.de> 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