The assertion in the following code fails unjustifiably:

#define __IBMCPP_TR1__ 1
#include <unordered_set>
#include <assert.h>
int main()
{
std::tr1::unordered_set<int> set1, set2;
set1.insert(1);
set1.insert(2);
set1.insert(3);
set1.insert(4);

set2 = set1;
set1 = set2;
assert (set1.find(1) != set1.end());

return 0;
}

To compile this code I used:
/usr/vacpp/bin/xlC test6.cpp
This happens with XlC 7.0, 8.0 and 9.0.
This also happens with unordered_map.
Similar problems seem to be present in the copy ctor of these classes
and the member function clear().
Any ideas?

TIA,
Ziv.