The LWG discussed this issue at the recent meeting in Kona Feb. 6-10, 2012. This is LWG issue 2113.
The LWG decided to mark LWG 2113 as NAD (not a defect), with the rationale that the standard is already clear that existing classes such as containers and std::string
can not be marked final by the implementation.
The discussion included the fact that while it may be frowned on to derive from such classes, it is clearly legal to do so in C++98/03. And making it illegal in C++11 would break far too much code.
Update
At this time, no library types in the current working draft are marked final
.
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