16 Library introduction [library]

16.5 Library-wide requirements [requirements]

16.5.5 Conforming implementations [conforming]

16.5.5.12 Derived classes [derivation]

1
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An implementation may derive any class in the C++ standard library from a class with a name reserved to the implementation.
2
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Certain classes defined in the C++ standard library are required to be derived from other classes in the C++ standard library.
An implementation may derive such a class directly from the required base or indirectly through a hierarchy of base classes with names reserved to the implementation.
3
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In any case:
  • (3.1)
    Every base class described as virtual shall be virtual;
  • (3.2)
    Every base class not specified as virtual shall not be virtual;
  • (3.3)
    Unless explicitly stated otherwise, types with distinct names shall be distinct types.178
4
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All types specified in the C++ standard library shall be non-final types unless otherwise specified.
178)
There is an implicit exception to this rule for types that are described as synonyms for basic integral types, such as size_­t and streamoff.
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