BDE 4.14.0 Production release
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#include <bslmf_isempty.h>
Private class: do not use outside of bslmf_isempty component. This component-private class is an example of an empty type, that can be used to calculate the likely size of an empty type on the current platform. As the inheritance-based technique used below disallows unions with a hard error, rather than a SFINAE-friendly failure, it is important to avoid instantiating the Imp
test unless there is a real chance that the type might be empty. While we cannot protect against testing small unions, we can rule out the more common cases where at least one union member has more than the smallest permissible size on the current ABI.