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Subject: Re: [boost] Official warnings policy?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-11-11 14:35:47

Paul A. Bristow wrote:
> Richard Webb wrote:
> >
> > Looks like the warnings occur depending on the types used
> > in the unit tests.
> > For example, the warning mentioned above comes from the test code:
> >
> > typedef variant< short, const char* > t_var2;
> > typedef variant< unsigned short, const char*, t_var2 > t_var5;
> > typedef variant< unsigned short, const char*, t_var5 > t_var6;
> >
> > t_var6 v6;
> > v6 = 58;
> >
> > Which looks like a legitimate warning about converting an
> > integer (58) to a short.
> Since this is expected, could the test use a static_cast to
> the right type?

The whole problem here is that the t_var6 type is driven by the template parameter list, so the range of that type may be insufficient, depending upon the template arguments. If the template doesn't validate the range of t_var6, then the assignment may overflow, just as the warning indicates.

I created a checked_cast that does a static_cast after validating against the upper and lower bounds, when necessary, for this very purpose. (Using TMP, it determines the signedness of the types involved, their relative sizes, etc., to compare as little as possible to validate the conversion.)

Rob Stewart robert.stewart_at_[hidden]
Software Engineer, Core Software using std::disclaimer;
Susquehanna International Group, LLP

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