Invalidating iterators c
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aims for full C++11 conformance except reasoned deviations, backporting as much as possible for C++03.Obviously, this conformance is a work in progress so this section explains what C++11 features are implemented and which of them have been backported to C++03 compilers. For compactness of container objects and for simplicity, it did not require containers to support allocators with state: Allocator objects need not be stored in container objects.
C++03 allowed implementors to suppose two allocators of the same type always compare equal (that means that memory allocated by one allocator object could be deallocated by another instance of the same type) and allocators were not swapped when the container was swapped.In C++11 move_if_noexcept is used to maintain C++03 exception safety guarantees combined with C++11 move semantics.This strong exception guarantee degrades the insertion performance of copyable and throwing-moveable types, degrading moves to copies when such types are inserted in the vector using the aforementioned members.This strong exception guarantee also precludes the possibility of using some type of in-place reallocations that can further improve the insertion performance of always uses move constructors/assignments to rearrange elements in the vector and uses memory expansion mechanisms if the allocator supports them, while offering only basic safety guarantees.If instantiated with only one allocator type, the inner allocator becomes the itself, thus using the same allocator resource for the container and every element within the container and, if the elements themselves are containers, each of their elements recursively.If instantiated with more than one allocator, the first allocator is the outer allocator for use by the container, the second allocator is passed to the constructors of the container's elements, and, if the elements themselves are containers, the third allocator is passed to the elements' elements, and so on.
implements C++14 Null Forward Iterators, which means that value-initialized iterators may be compared and compare equal to other value-initialized iterators of the same type.
Value initialized iterators behave as if they refer past the end of the same empty sequence (example taken from N3644): for either copyable or no-throw moveable classes.
C++11 further improves stateful allocator support through ), that allocator is also stored in the container and initialized from the user-supplied allocator when the container is constructed (i.e.
it's not constructed on the fly when auxiliary memory is needed).
is instantiated with one outer allocator and zero or more inner allocators.
A scoped allocator is a mechanism to automatically propagate the state of the allocator to the subobjects of a container in a controlled way.