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Re: C/C++ PATCH for c/77423 (bogus warning with -Wlogical-not-parentheses)
On 09/05/16 18:45, Joseph Myers wrote:
> On Mon, 5 Sep 2016, Marek Polacek wrote:
>
>> Still not sure about other operations. I guess no one would
>> object to warning on bool1 % bool2, but should we warn for
>> bool1 + bool2?
>
> I think boolean addition (with the result interpreted as an integer, not
> converted back to boolean) is perfectly reasonable - counting the number
> of flags that are true, for example (say if there are several conditions
> and it's an error for more than one of them to hold - of course that would
> be bool1 + bool2 + bool3 + bool4, etc.).
>
Yes, that's what I had in mind too. I think I even remember having seen
code like this, which is OK as long as the result is stored in an
integer variable.
But "if (bool1 + bool2)" should be written as "if (bool1 | bool2)",
and "if (bool1 * bool2)" should be written as "if (bool1 & bool2)".
I think a warning for boolean + and * suggesting to use | and &
is justified for clarity.
Bernd.