Re: Allowing duplicate template specialisations
Am 17.01.2011 12:50, schrieb Alexander Lamaison:
[..]
I wish it were just a theoretical issue to do with the spec but I actually
get a compiler error:
remote.cpp(94) : error C2766: explicit specialization;
'comet::comtype<IObjectWithSite>' has already been defined
object_with_site.hpp(41) : see previous definition of
'comtype<IObjectWithSite>'
The specialisations both look like this (i.e. they're identical):
template<> struct ::comet::comtype<::IObjectWithSite>
{
static const ::IID& uuid() throw() { return ::IID_IObjectWithSite; }
typedef ::IUnknown base;
};
with the original template like so:
template<typename T> struct comet::comtype
{
static const IID& uuid() throw()
{ return comtype<typename T::interface_is>::uuid(); }
typedef typename comtype<typename T::interface_is>::base base;
};
I understand that in the same compilation unit, the compiler has received
two separate definition but they're identical; can it not just choose one?
OK, so if I understand your use-case correctly you want support multiple
definitions of such entities in the *same* translation unit. This looks
odd to me, because there is a longstanding and general principle that
multiple definitions of entities (including class types, primary
templates or partial specializations as well as inline functions) shall
have only a single definition per translation unit. I wonder why you
cannot prevent this compiler error: Are these really two independent
inclusion headers with the same specialization definition which don't
share the same "inclusion guard"? How does this come?
Greetings from Bremen,
Daniel Kr?gler
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