Re: [boost] Current Guidance on Compiler Warnings?

Subject: Re: [boost] Current Guidance on Compiler Warnings?
From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2018-11-24 06:05:02

On Fri, Nov 23, 2018 at 9:48 PM Richard Hodges via Boost <
boost_at_[hidden]> wrote:
>
> On Fri, 23 Nov 2018 at 20:59, Emil Dotchevski via Boost <
> boost_at_[hidden]> wrote:
>
> > On Thu, Nov 22, 2018 at 12:56 AM Jayesh Badwaik via Boost <
> > boost_at_[hidden]> wrote:
> > >
> > > On Monday, 19 November 2018 21:02:55 CET Emil Dotchevski via Boost
wrote:
> > > > In that context there are probably legal reason for zero-warning
> > policy,
> > > > but it is not true that lack of warnings means fewer errors, in
fact it
> > > > could easily lead to more errors. For example warnings about
implicit
> > > > conversions are frequently "fixed" by replacing the implicit
conversion
> > > > with explicit conversion (cast). But the two are semantically very
> > > > different, and therefore one of them is incorrect, and very likely
that
> > is
> > > > the explicit one.
> > >
> > > Didn't know that. Can I see an example where the explicit warning is
> > > incorrect as opposed to implicit warning?
> >
> > I'm guessing you want an example where the explicit conversion is
> > incorrect, and you want to use an implicit conversion even though you
get a
> > warning. Here:
> >
> > unsigned f();
> >
> > void g( int x )
> > {
> >   if( x < f() ) //warning C4018: '<': signed/unsigned mismatch
> >   {
> >     ....
> >   }
> > }
> >
> > So you change that to:
> >
> > if( static_cast<unsigned>(x) < f() )
> >
>
> Better yet, provide a little library boilerplate and make the conversion
> explicit, correct and checkable at compile time:
>
> void g( int x )
> {
>   using result_type = decltype(f());
>   if(auto x_ = convert(to_type<result_type>, x) ; x_ < f())
>   {
>     foo();
>   }
> }

No, thank you, I prefer

if( x < f() )