Annex C (informative) Compatibility [diff]

C.2 C++ and ISO C++ 2003 [diff.cpp03]

C.2.13 [containers]: containers library [diff.cpp03.containers]

[container.requirements]
Change: Complexity of size() member functions now constant.

Rationale: Lack of specification of complexity of size() resulted in divergent implementations with inconsistent performance characteristics.

Effect on original feature: Some container implementations that conform to C++ 2003 may not conform to the specified size() requirements in this International Standard.
Adjusting containers such as std​::​list to the stricter requirements may require incompatible changes.
[container.requirements]
Change: Requirements change: relaxation.

Rationale: Clarification.

Effect on original feature: Valid C++ 2003 code that attempts to meet the specified container requirements may now be over-specified.
Code that attempted to be portable across containers may need to be adjusted as follows:
[container.requirements]
Change: Requirements change: default constructible.

Rationale: Clarification of container requirements.

Effect on original feature: Valid C++ 2003 code that attempts to explicitly instantiate a container using a user-defined type with no default constructor may fail to compile.
[sequence.reqmts], [associative.reqmts]
Change: Signature changes: from void return types.

Rationale: Old signature threw away useful information that may be expensive to recalculate.

Effect on original feature: The following member functions have changed:
Valid C++ 2003 code that relies on these functions returning void (e.g., code that creates a pointer to member function that points to one of these functions) will fail to compile with this International Standard.
[sequence.reqmts], [associative.reqmts]
Change: Signature changes: from iterator to const_­iterator parameters.

Rationale: Overspecification.

Effect on original feature: The signatures of the following member functions changed from taking an iterator to taking a const_­iterator:
Valid C++ 2003 code that uses these functions may fail to compile with this International Standard.
[sequence.reqmts], [associative.reqmts]
Change: Signature changes: resize.

Rationale: Performance, compatibility with move semantics.

Effect on original feature: For vector, deque, and list the fill value passed to resize is now passed by reference instead of by value, and an additional overload of resize has been added.
Valid C++ 2003 code that uses this function may fail to compile with this International Standard.