Past-the-end iterator invalidation in C++11

Question

The most popular post on C++ Iterator invalidation rules claims that it\'s not clear if the past-the-end iterators (i.e., those returned by end(), cend()<

Answer 1

You should be able to trust it if the standard says the operation will not invalidate iterators. Anything else should be treated as a bug in the standard library implementation.

Answer 2

My question is about all containers:

• In C++11, are there any container operations that may invalidate a past-the-end iterator, and where this behavior is ambiguous in the language specification?

I am not sure what you mean with "where this behavior is ambiguous in the language specification", but there certainly are operations that invalidate past-the-end operators (like insert into a std::vector or std::string).

Said differently,

• Can I trust the validity of a past-the-end iterator after performing a container operation that does not say it may invalidate the past-the-end iterators?

You can trust the past-the-end iterator like any other iterator: Any operation that does not (potentially) invalidate iterators won't invalidate them. Except for the possibility of the standard sporting a bug, that is all operations where it doesn't say that they (potentially) invalidate operators.

Answer 3

At least in GCC end iterator gets invalidated for std::map:

#include <set>
#include <stdlib.h>
#include <assert.h>
int main() {
  std::set<int> a;
  a.insert(1);
  std::set<int>::reverse_iterator rit(a.rbegin());
  ++rit;
  assert(rit==a.rend());
  a.erase(a.begin());
  assert(a.rend()==rit); // FAIL
}