What will happen if I keep incrementing an iterator?

Question

I have a simple question: what will happen if I keep incrementing an iterator when it reaches the end() (one past the last) of a C++ STL container? e.g.

set<int> intSet;
intSet.insert(0);
intSet.insert(1);
intSet.insert(2);
set<int>::iterator setIter = intSet.begin();
for (int i = 0; i < 10; i++)
  setIter++;

so, will setIter always be intSet.end()? or this is an undefined behavior (can give me inconsistent junk)?

@Tahlil Probably, (s)he afraids to damage the universe, because we can not know what will happen. — Ivan Aksamentov - Drop, Apr 24 '14 at 01:47
@Tahlil just because it might work does not mean it is guaranteed to work. — Joe, Apr 24 '14 at 01:57
@Joe My question had the purpose of him telling us what research he had done before asking the question. Nothing else :) — Tahlil, Apr 24 '14 at 02:05

score 1 · Answer 1 · answered Apr 24 '14 at 01:44

1

It will throw a runtime error in VS2013. However, it will not in G++ (ideone). However it is undefined behavior if you ever use it. It is definitely not equal to intSet.end()

answered Apr 24 '14 at 01:44

yizzlez

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score 0 · Accepted Answer · edited May 23 '17 at 12:11

0

The mere act of incrementing it will do nothing, at least in the GNU compilers.

If you try to dereference it, that invokes undefined behavior.

See this question for more discussion.

edited May 23 '17 at 12:11

Community

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answered Apr 24 '14 at 01:46

merlin2011

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Thx, yes, I know I should not dereference it. I just need to know if this can give me consistent behavior. Seems like it won't if I use different compilers. – user3277360 Apr 24 '14 at 02:05

What will happen if I keep incrementing an iterator?

2 Answers2