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Re: RFC: -Wall by default
On 04/11/2012 05:18 PM, Ian Lance Taylor wrote:
> Andrew Haley <aph@redhat.com> writes:
>
>> On 04/05/2012 01:28 PM, Michael Veksler wrote:
>>
>>> As for specific warnings, I hate that the the code (a&&b || c&&d),
>>> which did not cause a warning on older gcc version now gives a
>>> warning. I would not want it on by default since it forces users to
>>> write too many parentheses in ((a&&b)||(c&&d)) which makes the
>>> expression less readable. What next? Warn about (a*b+c*d) ? I would
>>> hate to write ((a*b)+(c*d)).
>>>
>>> Sure, the precedence of: << vs. +; & vs. == ; & vs. && ; is less
>>> clear and deserves a warning, but: & vs. | ; && vs. || ; are at
>>> least as common as * vs. + that programmers ought to know them.
>>
>> Absolutely so, yes. I'd consider this a bug in gcc, just as if it
>> warned for arithmetic.
>
> This one is an interesting case, since there are strong arguments on
> both sides.
>
> I enabled the C++ warning about the precedence of && and || (it's been
> in C for many years). It found real bugs in real code, bugs that had
> existed for years.
It's the balance with false positives, as usual. If you're looking
for a good example of a warning that is useful but still triggers with
perfectly legal (and reasonable) code, this is a great example.
Andrew.