On Oct 12, 2012, at 12:38 PM, Richard Trieu <[email protected]> wrote:

> This patch is for a new warning to Clang, called -Wlogical-not-compare.  It 
> is designed to catch the case where the user is attempting to negate a 
> comparison, but only manages to negate the LHS because of missing parens.  
> For instance, warn here:
> 
>      if (!x < 5)
> 
> The user probably meant:
> 
>      if (!(x < 5))
> 
> or
> 
>      if (x >= 5)
> 
> When emitted, the warning will have a note suggesting this as a fix-it (drop 
> the not and inverting the comparison operator).

If x has FP type, then !(x < 5) is not equivalent to (x >= 5); if x is NaN, the 
first is true, but the second is false.

- Steve
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