Is Visual Studio recursive_directory_iterator.pop() broken? - c++

Question

Given an example directory tree for testing:
Root
A
A1
A2
B
B1
B2
I wish to recursively enumerate the directories, but skip the processing of directory A completely.
According to the MSDN documentation code something like the following should do the job:
void TestRecursion1()
{
path directory_path("Root");
recursive_directory_iterator it(directory_path);
while (it != recursive_directory_iterator())
{
if (it->path().filename() == "A")
{
it.pop();
}
else
{
++it;
}
}
}
...it does not. MSDN for recursive_directory_iterator.pop() states
If depth() == 0 the object becomes an end-of-sequence iterator.
Otherwise, the member function terminates scanning of the current
(deepest) directory and resumes at the next lower depth.
What actually happens is that due to a short circuit test in pop() if 'depth == 0' nothing happens at all, the iterator is neither incremented nor does it become the end of sequence iterator and the program enters an infinite loop.
The issue seems to be that semantically pop() is intended to shunt processing of the tree to the next level higher than the current level, whereas in this example I wish to skip processing of A and continue processing at B. The first problem is that both these directories (A and B) exist at the same level in the tree, the second problem is that this level is also the top level of the tree so there is no higher level at which to resume processing. All that said it still seems like a bug that pop() fails to set the iterator to the end-of-sequence iterator thus causing an infinite loop.
After this testing I reasoned that if I can't pop() A directly, I should at least be able to pop() from any child of A and achieve a similar result. I tested this with the following code:
template<class TContainer>
bool begins_with(const TContainer& input, const TContainer& match)
{
return input.size() >= match.size()
&& equal(match.begin(), match.end(), input.begin());
}
void TestRecursion2()
{
path base_path("C:\\_Home\\Development\\Workspaces\\Scratch \\TestDirectoryRecursion\\bin\\Debug\\Root");
recursive_directory_iterator it(base_path);
while (it != recursive_directory_iterator())
{
string relative_path = it->path().parent_path().string().substr(base_path.string().size());
cout << relative_path << "\n";
if (begins_with(relative_path, string("\\A")))
{
it.pop();
}
else
{
cout << it->path().filename() << " depth:" << it.depth() << "\n";
++it;
}
}
}
Here I test every item being processed to determine whether its parent is Root\A, and if it is call pop(). Even this doesn't work. The test correctly identifies whether a node in the tree is a child of A and calls pop() accordingly, but even at this deeper level pop() still fails to increment the iterator, again causing an infinite loop. What's more, even if this did work it would still be very undesirable since there is no guarantee of the order in which sub nodes are enumerated, so despite the test to check whether a particular node is a child of A because those nodes might be indirect children you could still end up processing a goodly amount of A anyway.
I think my next course of action is to abandon use of this recursive_directory_iterator and drive the recursion manually using a standard directory_iterator, but it seems as if I should be able to achieve what I need more simply with the recursive_directory_iterator but I'm getting blocked at every turn. So my questions are:
Is the recursive_directory_iterator.pop() method broken?
If not how do I use it to skip the processing of a directory?

Answer 1

Isn't the code you want more like the following, using disable_recursion_pending()?
while (it != recursive_directory_iterator())
{
if (it->path().filename() == "A")
{
it.disable_recursion_pending();
}
++it;
}