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

[Caolán McNamara]

On Wed, 2012-02-29 at 12:13 +0100, 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.
> 
> Back in November, I wrote a prototype _actually_ safe versions, but
> got sidetracked and forgot about them. I'm unearthing them again now,
> attached.

It might be a little orthogonal to just the cast issue, but I wonder if 

Cert's IntegerLib or SafeInt (http://safeint.codeplex.com/) or somesuch
(https://bugzilla.mozilla.org/show_bug.cgi?id=555798) covers the same
ground and is license-suitable as a drop in ?

C.