Re: [boost] Official warnings policy?

Subject: Re: [boost] Official warnings policy?
From: Paul A. Bristow (pbristow_at_[hidden])
Date: 2009-11-12 10:18:24

> -----Original Message-----
> From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]] On
Behalf Of
> John Maddock
> Sent: Thursday, November 12, 2009 1:04 PM
> To: boost_at_[hidden]
> Subject: Re: [boost] Official warnings policy?

> Delving into this a bit deeper, I believe the warning is correct, and cannot
> / should not be fixed, to recap we have:
> 
> d:\data\boost\trunk\boost/variant/variant.hpp(1297) : warning C4244:
> 'argument' : conversion from 'const int' to 'const short', possible loss of
> data
<snip> 
> The code calls Variant's converting-assignment operator, and Boost.Variant
> internally decides what type to convert the argument to and makes the
> assignment.  In this case the user *should* see a warning to be alerted to
> the fact that the internal conversion results in loss of precision (likewise
> they would see an error in this location if there is no suitable
> conversion).
> 
> I notice that the code in question has a comment to this effect:
> 
>             // NOTE TO USER :
>             // Compile error here indicates one of the source variant's types
>             // cannot be unambiguously converted to the destination variant's
>             // types (or that no conversion exists).
> 
> But perhaps we should add a similar note about compiler warnings?

Yes.

If the intention (boring) of the test is to provide an unsigned short int '58US'
or static_cast<unsigned short int>(58), then there should not be a warning,

but I agree that it is probably intended (more interestingly)  to provide an
unsigned int (58) and demonstrate that this will involve loss of precision and
*will* give a warning.

But it does need a comment.

Paul

---
Paul A. Bristow
Prizet Farmhouse
Kendal, UK   LA8 8AB
[phone], mobile [phone]
pbristow_at_[hidden]