Re: Wshadow: Better name for 'optarg'?

[Thomas Huth <thuth@redhat.com>]

On 04/10/2023 19.43, Philippe Mathieu-Daudé wrote:
> On 4/10/23 19:35, Thomas Huth wrote:
>> On 04/10/2023 19.23, Richard Henderson wrote:
>>> On 10/4/23 03:05, Philippe Mathieu-Daudé wrote:
>>>> Hi,
>>>>
>>>> I'm getting a bunch of errors for 'optarg' declared in <unistd.h>:
>>>
>>> I thought things like this is why we were trying -Wshadow=local.
>>>
>>> I think it's unlikely that we'll be able to prevent all such cases.
>>
>> Given the broad range of operating systems and libraries that we support 
>> in QEMU, I agree with Richard - it will likely be impossible to enable 
>> that option without =local by default without risking that compilation 
>> breaks on some exotic systems or new versions of various libraries.
> 
> -Wshadow=local doesn't seem to work here which is why I switched
> to -Wshadow. I probably misunderstood something from Markus cover
> letter. My setup is:
> 
> C compiler for the host machine: clang (clang 14.0.3 "Apple clang version 
> 14.0.3 (clang-1403.0.22.14.1)")
> 
> I suppose we'll figure that out when eventually enabling -Wshadow=local
> on CI. Meanwhile I already cleaned the 'optarg' warnings that were
> bugging me, see:
> https://lore.kernel.org/qemu-devel/20231004120019.93101-1-philmd@linaro.org/
> I'll try to get -Wshadow=local, but the other series still seems a
> good cleanup, as I used more meaningful variable names.

If I got that right, -Wshadow=local only works with gcc and not with clang 
yet, so we'll need a check in configure or meson.build and will be able to 
only use it when it's available.

If we could use "-Wshadow" to check global variables, too, that would be 
great, but given my experience with some other project, it's very unlikely 
that you can get it running reliably everywhere, since there is often a bad 
library header somewhere that declares some global variable(s) that spoil 
your plans (IIRC I've once seen a bad library that even declared a global 
variable called "x" ... and you certainly don't want to rename all 
occurances of "x" in the QEMU source code just because of a bad library ... 
however, that's been many years ago, though, maybe the situation got better 
nowadays, so if you like, feel free to continue your quest - just be aware 
that it might not be solvable at the end).

  Thomas