Re: [PATCH] Make -Wint-in-bool-context warn on suspicious shift ops

[Bernd Edlinger <bernd.edlinger@hotmail.de>]

On 09/28/16 16:41, Jason Merrill wrote:
> On Tue, Sep 27, 2016 at 11:10 AM, Bernd Edlinger
> <bernd.edlinger@hotmail.de> wrote:
>> On 09/27/16 16:42, Jason Merrill wrote:
>>> On Tue, Sep 27, 2016 at 10:28 AM, Bernd Edlinger
>>> <bernd.edlinger@hotmail.de> wrote:
>>>> On 09/27/16 16:10, Florian Weimer wrote:
>>>>> * Bernd Edlinger:
>>>>>
>>>>>>> “0 << 0” is used in a similar context, to create a zero constant for a
>>>>>>> multi-bit subfield of an integer.
>>>>>>>
>>>>>>> This example comes from GDB, in bfd/elf64-alpha.c:
>>>>>>>
>>>>>>> |   insn = INSN_ADDQ | (16 << 21) | (0 << 16) | (0 << 0);
>>>>>>>
>>>>>>
>>>>>> Of course that is not a boolean context, and will not get a warning.
>>>>>>
>>>>>> Question is if "if (1 << 0)" is possibly a miss-spelled "if (1 < 0)".
>>>>>>
>>>>>> Maybe 1 and 0 come from macro expansion....
>>>>>
>>>>> But what's the intent of treating 1 << 0 and 0 << 0 differently in the
>>>>> patch, then?
>>>>
>>>> I am not sure if it was a good idea.
>>>>
>>>> I saw, we had code of the form
>>>> bool flag = 1 << 2;
>>>>
>>>> another value LOOKUP_PROTECT is  1 << 0, and
>>>> bool flag = 1 << 0;
>>>>
>>>> would at least not overflow the allowed value range of a boolean.
>>>
>>> Assigning a bit mask to a bool variable is still probably not what was
>>> intended, even if it doesn't change the value.
>>
>> That works for me too.
>> I can simply remove that exception.
>
> Sounds good.
>

Great.  Is that an "OK with that change"?


Bernd.