At 10:48 AM +0000 7/14/09, Alexander Nasonov wrote:
boost::scope_exit::aux::holder< boost::scope_exit::aux::declare< sizeof(boost_scope_exit_args)
::apply<0>::apply_value boost_scope_exit_args;
If sizeof(boost_scope_exit_args) is equal to sizeof(declared), the resulting type would be holder<(0<0>::apply_value)>. But I don't see a global variable apply_value in your patch.
The added parenthesis in the above, in holder<(0<0>::apply_value)> don't describe the actual parse and evaluation. Instead, that snippet gets parsed and evaluated as holder<(0<0)>::apply_value so that the whole (expression) statement (with disambiguating parenthesis added) is holder<(0<0)>::apply_value > boost_scope_exit_args;
BTW, I modified Steven's code and introduced a bug because sizeof(declare<sizeof(undeclared)>::apply<0>) does not necessarily equal to sizeof(declared).
Are you sure? Perhaps I'm missing something, but it looks to me like those values should indeed be the same. The "apply" class template in question has one member, of type "declared". Given that, I would be surprised if the "apply" class template could have a different size (or alignment) from the "declared" type.