In the section «10.2 Export declaration» of the C++ 20 Standard there is written
 
2 A declaration is exported if it is
(2.2) — a namespace-definition that contains an exported declaration, or
 
But then there is followed an example
 
export namespace N { } // OK
 
but this namespace definition does not contain an exported declaration.  It is an empty namespace definition.
 
So is there a contradiction?
 
You can meet me at http://cpp.forum24.ru/ or www.stackoverflow.com or http://ru.stackoverflow.com