I just started playing around with the auto keyword of the new C++ standard. I assumed a variable declared with auto would have the type of the according expression.

Though consider the following example:

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#include <vector>

using namespace std;

vector<int> data;

vector<int>& getData()
{
  return data;
}

int main( int argc, const char* argv[] )
{
  data.push_back(1);

  auto data2 = getData();
  data.push_back(2);
}

Looking at the variables in the debugger, you see that data contains the values 1 and 2, whereas data2 only contains 1, thus data2 is not the same object as data. I assumed data2 was of type vector<int>& (the return type of getData), though it obviously just is vector<int>.

Declaring it as

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auto& data2 = getData();

works though. data2 is now a reference to data.

It makes sense, the standard defines it that way. Otherwise, how could you create a copy of the return value? Still it makes using auto a little more confusing …