Re: [ros-dev] Replacing unsafe TRUE comparisons (Following Re: bool => BOOL)

[Love Nystrom]

On 2014-11-16 05.22, Timo Kreuzer wrote:
>   Am 14.11.2014 15:32, schrieb Love Nystrom:
> >  
> >  On 2014-11-14 00.41, Alex Ionescu wrote:
> > >   I would much rather see if (f != FALSE) instead
> > > of if ( f ). 
> >  Well, it's certainly a valid option, and C++ compilers seem to
> > generate
> >  [abbrev] 
>  "if (f != FALSE)" and "if (f)" are exactly 100% the
> same for the 
>  compiler. "if (f)" is nothing but a synonym for "if (f != 0)" and 
>  FALSE is 0.  
Well... Actually not exactly the same.. ;)
"if (f != FALSE)" requires an explicit comparison with a second operand,
whereas "if ( f )" can be performed by comparing the value *with itself* 
using an OR instruction.
You'll see that a lot in the C string library (I think you know this), 
where it's used to check quickly
for the terminating NUL without having to compare with a second operand.

Best Regards
// Love

>   Whether it creates a CMP, or an OR or a TEST is all up
> to the compiler 
>  and it will be the same in both cases. If it was not the same, there 
>  is something ... well not neccessarily "wrong" but at least very 
>  strange with the compiler.
>
> >  
> >  I expect some people will use the former.
> >  Personally I much prefer the latter. 
>  I think both have their pros and cons. So I
> don't really care.
>
>