I mistakenly took the address of the reference returned by the back() operator in an empty container and was surprised to see that the address wasn't zero.
If a container e.g. std::deque is empty, what does back() return?
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93answers:
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+7
A:
it returns the last element.
on this page: http://www.sgi.com/tech/stl/BackInsertionSequence.html
precondition: !a.empty()
Equivalent to *(--a.end()).
since the precondition is the deque is not empty, then it means it's undefined behavior.
Chris H
2010-02-04 22:29:09
It also means that is it most likely one element just before the "logical" place for the first element. I should say that the behavior of `front` is logically the same though the address will be the "logical" place I was talking about (for an array-like container).
Matthieu M.
2010-02-05 08:05:17
+1
A:
Calling front or back on an empty standard container results in undefined behavior.
AndreyT
2010-02-04 23:02:25