From: David Abrahams (dave_at_[hidden])
Date: 2005-10-26 07:18:10
Michael Shepanski <mshepanski_at_[hidden]> writes:
> The code below fails a compile-time assertion in boost 1.32.0 on MSVC 7.1.
> This is because, internally, boost::optional uses boost::alignment_of, which
> produces the number 12, which is then passed as a template parameter to
> boost::type_with_alignment, which won't accept 12.
> Not sure where the blame lies. Is it with boost::alignment_of, for
> 12 in the first place? Perhaps not, since 12 is a multiple of 4, and the
> says boost::alignment_of is allowed to produce any multiple of the actual
> alignment value. So is the fault with boost::type_with_alignment, for not
> accepting 12? Or is there something wrong with the app?
I think the problem is that type_with_alignment can't find a type that
has an alignment of 12. Producing an error in that case is the right
behavior. We could add the type whose alignment_of<> is 12 to the
reperotoire of types being tested by type_with_alignment...
> #include <boost/optional.hpp>
> class D
> virtual ~D();
> class E : virtual public D
> virtual ~E();
> unsigned long long m_i;
> boost::optional<E> s_optE;
> --- Michael Shepanski
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-- Dave Abrahams Boost Consulting www.boost-consulting.com
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