[C/C++ PATCH] Implement -Wtautological-compare (PR c++/66555, c/54979)

[Richard Earnshaw]

On 22/07/15 19:43, Martin Sebor wrote:
> On 07/14/2015 09:18 AM, Marek Polacek wrote:
>> Code such as "if (i == i)" is hardly ever desirable, so we should be able
>> to warn about this to prevent dumb mistakes.
> 
> I haven't tried the patch or even studied it very carefully but
> I wonder if this is also the case when i is declared volatile.
> I.e., do we want to issue a warning there? (If we do, the text
> of the warning would need to be adjusted in those cases since
> the expression need not evaluate to true.)
> 
> Martin
> 

It's also not true if i is an IEEE floating point type with a NaN value.
 In that case this is a standard idiom for testing for a NaN.

R.