Re: [boost] [new Warnings policy] MS C4180 on the Maintenance Guidelines

Subject: Re: [boost] [new Warnings policy] MS C4180 on the Maintenance Guidelines
From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2009-11-17 10:36:01

Gottlob Frege wrote:
> On Mon, Nov 16, 2009 at 4:08 PM, Patrick Horgan <phorgan1_at_[hidden]> wrote:
>>   C4800 Might suggest that they use a bool valued expression in the first
>>   place, i.e. instead of foo, foo!=0, or do a static cast to bool.  This is at
>>   times indicative of real bugs, when people turn out to not be doing what
>>   they thought they were doing.  Apparently this is one of my favorite bugs
>>   (by favorite I don't mean that I like it either!)
> 
> C4800: int' : forcing value to bool 'true' or 'false'
> 
> I'm a big fan of using !! to convert to bool:
> 
> bool has_item()
> {
>     Foo * foo = find_item();
> 
>     return !!foo; // convert ptr to bool
> }
> 
> Is that too subtle for others?  It wouldn't be too subtle if it became
> a common idiom. :-)

It looks like a quite recommended idiom (double-bang trick)

http://www.artima.com/cppsource/safebool.html

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org