Re: [boost] Deterimining interest in: Optional Polymorphic Value object with Small Object optimization

From: Steven Watanabe (steven_at_[hidden])
Date: 2007-10-21 21:22:04

AMDG

Mathias Gaunard <mathias.gaunard <at> etu.u-bordeaux1.fr> writes:

> The problem with small object optimization is that you get the same 
> issue that boost.variant has: it's hard to maintain the never-empty 
> guarantee in operator=, because the copy constructor of a new value can 
> throw and thus you lose the old value.

When I was trying to do this I only used the small
object optimization for types that I knew to have a no-throw
copy constructor  (i.e. builtin types at the moment).  In C++Ox
this can be loosened to having a no-throw move constructor.

> I wonder, by the way, how boost.function solves that issue.

It doesn't.  Boost.Function can be empty and assignment for
Boost.Function does not provide the strong guarantee of
exception safety.

In Christ,
Steven Watanabe