Compiler warning when using boost::blank in a boost::variant - c++

Question

I'm getting a warning for the following code, which dissapears if I remove boost::blank from the variant:
namespace DB
{
struct Value{};
struct Container{};
}
typedef boost::variant <boost::blank, DB::Value, DB::Container> CommandData;
struct Command {
explicit Command(CommandData& _data): data(_data){
}
CommandData data;
};
int main()
{
CommandData commandData;
Command command(commandData);
return 0;
}
What's this issue?
Here's the warning:
1>: warning C4345: behavior change: an object of POD type constructed with an initializer of the form () will be default-initialized
1> c:\boost_1_49_0\boost\variant\variant.hpp(1224) : while compiling class template member function 'boost::variant<T0_,T1,T2>::variant(void)'
1> with
1> [
1> T0_=boost::blank,
1> T1=DB::Value,
1> T2=DB::Container
1> ]
1> c:\code.h(38) : see reference to class template instantiation 'boost::variant<T0_,T1,T2>' being compiled
1> with
1> [
1> T0_=boost::blank,
1> T1=DB::Value,
1> T2=DB::Container
1> ]

Answer 1

That warning is rather dumb. It warns that MSVC now does the right thing as opposed to some ancient version. You can turn it off with a pragma.

Answer 2

It's not because of the variant. Try to put int as a struct member for example instead of variant, and you'll get the same warning. The thing is that variant initializes with the first value by default, and boost::blank is a spectial type to optimize the variant behavior. See the variant documentation in Boost