Re: [protoPATCH] "safe" numeric casts with explicit min/max

HI Stephan,

On Wed, 2012-02-29 at 15:25 +0100, Stephan Bergmann wrote:
> On 02/29/2012 12:13 PM, Lionel Elie Mamane wrote:
> > Background: we have in sc/source/filter/inc/ftools.hxx supposedly
> > "safe" casts that are (according to the Doxygen documentation)
> > supposed to be safer than just static_cast. As fdo#39589 uncovered,
> > they are actually so buggy as to be *less* safe.
>
> Are those "saturating" ulimit_cast a good thing, anyway?  Looks like 
> they are only used in a handful of sc/source/filter/excel/ files. 

That's my take also. Their uses are very limited, and there are
alternatives we could use (SafeInt, boost::numeric_cast) if we really
have to use one.

> Picking the first occurrence at random,
>
> > return ulimit_cast< sal_uInt16 >( nValueCount, EXC_CHDATAFORMAT_MAXPOINTCOUNT );
>
> from XclExpChSourceLink::ConvertDataSequence (xechart.cxx), where 
> nValueCount is a sal_uInt32 quantity -- is it OK to silently truncate 
> this quantity here, or does it rather indicate a conversion failure that 
> should be reported to the user?

I personally think it's perfectly okay to just truncate the value in
this particular case.

Kohei

-- 
Kohei Yoshida, LibreOffice hacker, Calc