How to use an argument as return value in gmock

Question

I have the following call:

EXPECT_CALL(myMock, myFunction(someSpecifiedParameter, _, _))
      .WillOnce(DoAll(SaveArg<2>(&bufferSize), Return(make_pair(Success, bufferSize))));

I'm trying to return whatever value that is passed as the second _ as my second element in the pair. Is it the best (or at least right) way to do it?

This bufferSize variable was declared in the test class.

EDIT:

Putting in other words:

Suppose I have the following:

class object{
    pair<int, int> f(int x);
}

object obj;
constexpr int fixedValue = 5;
EXPECT_CALL(obj, f(_)).WillOnce(
                       Return(make_pair(fixedValue, <PARAMETER PASSED TO F>));