New subject: variant no compile time check on get<> type parameter

19 Mar 2007

      Hello

In order to minimize heap allocations but still allow for some OOP designs I 
needed a sort of union but one that it works for more than POD types. So I 
implemented such a thing myself to find out recently that boost::variant 
might do this already (boost does that often ;) ).

However, initial testing for boost::variant shows that that there is no 
compile time check on the types allowed to instantiate boost::get on a 
variant, example:

struct A {}; struct B {}; struct C{};

int main()
{
	boost::variant v v;
	boost::get<C>(v);
}

Compiles fine (gcc 4.1.1, boost 1.33.1) but errors at runtime throwing a 
bad_get exception from get. It seems to me that the get<> on variant somehow 
works for any type not checking if the type parameter for get matches one in 
the type sequence of the given variant.

Maybe I miss something but shouldn't get on variant have a compile time type 
check ? (this would catch at compile time common errors for variant use cases 
I think)

-- 
Mihai RUSU					Email: dizzy@roedu.net
GPG : http://dizzy.roedu.net/dizzy-gpg.txt	WWW: http://dizzy.roedu.net
			"Linux is obsolete" -- AST

variant no compile time check on get<> type parameter

Dizzy

Yuval Ronen

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