Exception Requirements on Standard Containers

Question

C++11 §23.2.1.10 specifies:

Unless otherwise specified all container types defined in this Clause meet the following additional requirements:

• if an exception is thrown by an insert() or emplace() function while inserting a single element, that function has no effects.
• no erase() , clear() , pop_back() or pop_front() function throws an exception.

Regarding the first bullet point, How does the container guarantee that? The constructor for T might have side-effects. Should it not be "has no effect on the container"

Regarding the second bullet point, This normally calls allocator::deallocate(T*,size_t) which is not noexcept. Why should eventual exceptions be masked away?

Answer 1

Table 28 specifies one of the requirements of an allocator is that deallocate() "Does not throw exceptions". That is how the standard can make the assertion about erase(), clear(), pop_back() and pop_front()