std::unordered_multiset exception iterating bucket-CodePudding

My test case is the one shown below:

std::size_t t(const int &i) { return i | 0b01010101010101010101010101010101; }

int main()
{
    std::unordered_multiset<int, decltype(&t)> um(100, t);
    um.insert(9872934);
    um.insert(9024582);
    um.insert(2589429);
    um.insert(2254009);
    um.insert(3254082);
    um.insert(3945820);
    um.insert(8347893);

    auto intf = t(9872934);
    for (auto cb = um.begin(intf), end = um.end(intf); cb != end;   cb)
    {
        std::cout << *cb;
    }
};

Debugging with Microsoft Visual Studio Community 2022 v17.1.2 an exception is thrown constructing the iterator; first I thougth that the hash function (t) could be the one to blame so I've tried this:

std::unordered_multiset<int> um; // no custom hash, just multiset of integers...
um.insert(9872934);
um.insert(9024582);
um.insert(2589429);
um.insert(2254009);
um.insert(3254082);
um.insert(3945820);
um.insert(8347893);

auto intf = t(9872934);
for (auto cb = um.begin(intf), end = um.end(intf); cb != end;   cb)
{
    std::cout << *cb;
}

But it behaves the same way, even in online compilers (check it out). What I'm missing? How should I make this work?

CodePudding user response：

The argument to the begin(bucket) function is the bucket number not the key.

You need use bucket to get the bucket number that corresponds to the key

auto intf = um.bucket(t(9872934)); <<<====
for (auto cb = um.begin(intf), end = um.end(intf); cb != end;   cb)
{
    std::cout << *cb;
}