c++

The most popular post on C++ Iterator invalidation rules claims that it's not clear if the past-the-end iterators (ie, those returned by end() , cend() , rend() , and crend() ) are invalidated according to the same rules as normal iterators, which point to elements in the container. These claims, made for both 2003 and 2011 C++, defer to a post discussing End iterator invalidation rules, where the accepted answer suggests that the 2003 standard is ambiguous on the matter. This conclusion is based on a comment in 23.1/10 (in the context of swap() ) that seems to imply that when the spec does not explicitly mention invalidation of past-the-end iterators, they may be invalidated.

A comment on that post's question (by mike-seymour) suggests that C++11 is unambiguous on this matter, in the case of deque s. 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?

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?

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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.

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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.

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至少在GCC中，迭代器对std :: map无效：

#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
}

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