Boost C++ Libraries: Ticket #8069: Boost unordered_map iterator bug

attachment set

Fri, 15 Feb 2013 15:04:36 GMT

attachment → main.cpp

component changed; owner set

viboes — Fri, 15 Feb 2013 17:18:00 GMT

owner set to Daniel James
component None → unordered

Daniel James — Fri, 15 Feb 2013 20:38:13 GMT

The iterator is still valid, it's pointing at '0' which is the last element in the container, so your loop only prints out that element. Try printing out all the elements and you can see that the '0' comes last. Remember that these are unordered containers, so there's no guarantee that they'll have any particular order.

Fri, 15 Feb 2013 23:40:31 GMT

Thanks for the reply.

I don't expect unordered map (keys) following a specific order. I thought that if i insert into an unordered map (e.g int->int) the pairs 0->5, 4->3, 6->9, 2->0 and before the insert of the pair 6->9 take the iterator of map[4 ] then after the insertion of the last pair, i can print out map[4 ], map[6 ] and map[2 ] using the operator ++. This is very useful in case of large unordered maps and multithreading (one thread inserts/looksup elements and another one checks every x seconds (the next) y map's elements, not simultaneously).

Steven Watanabe — Sat, 16 Feb 2013 00:09:14 GMT

You're assuming that the order of the elements in the container is the same as the insertion order. This is not the case. map[6] and map[2] could just as easily appear before map[4] when iterating over the container and in fact, as Daniel stated, this is what is happening in your test case.

status changed; resolution set

Daniel James — Sun, 17 Feb 2013 22:14:43 GMT

status new → closed
resolution → invalid