question regarding new warning

[Daniel Gutson]

On Thu, Mar 27, 2014 at 6:48 AM, Manuel López-Ibáñez
<lopezibanez@gmail.com> wrote:
> On 27/03/14 09:52, Florian Weimer wrote:> On 03/27/2014 08:44 AM,
> Andrew Haley wrote:
>>
>>> On 03/26/2014 03:05 PM, Daniel Gutson wrote:
>>>
>>>>      assigning a negative literal to an unsigned variable issues no warning:
>>>>
>>>>
>>>>     unsigned int x;
>>>>     x =- 4;
>>>>
>>>> This is specially important in typos when -= was intended instead of =-
>>>>
>>>> Would be acceptable if I add a new warning to handle this, i.e.
>>>>    -Wnegative-to-unsigned
>>>> or alike?
>>>
>>> Assigning a negative literal to an unsigned variable is well-defined
>>> standard C.  Is it really appropriate to warn for correct code?
>>
>> Yes, this warning needs to take whitespace into account.  But then, I suppose
>> it would be fine.
>>
>
> This is already warned by -Wconversion/-Wsign-conversion since at
> least GCC 4.6 (but I think probably since GCC 4.3):
>
> test.c: In function 'foo':
> test.c:4:8: warning: negative integer implicitly converted to unsigned
> type [-Wsign-conversion]
>      x =- 4;
>         ^

I didn't have such warning in my radar. Good one!

>
> There are some known bugs in -Wconversion and nobody working on them,
> so if you are still interested in helping, I can give you some hints
> on where your help will be very welcome.

Could you please go ahead and show me the failing cases?
I only worked in the backend, but I'd like to take a look to the front-end.

There's also all the other commenters of my post regarding the =- and
=+ looking-like operators, which should take ws into account.

>
> Cheers,
>
> Manuel.



-- 

Daniel F. Gutson
Chief Engineering Officer, SPD


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