Return conditional `range_expression`

What's the most efficient way of iterating over one of several known ranges based on some condition?

pseudo-code for a binary condition:

for element in (condition ? range_a : range_b)
  // do work

This 'example' shows my intention using a range-based for loop but as std::initializer_list has reference semantics it won't work.

constexpr auto some_range(bool c) -> std::initializer_list<int> {
  if (c) {
    return {1,2};
  } else {
    return {3, 4, 5};
  }
}

bool cond = true; // false

for(auto x : some_range(cond)) {
  // things
}

yields: warning: returning address of local temporary object [-Wreturn-stack-address]

During run-time I could return a std::vector but that would involve constructing a new vector every call:

auto some_range(bool c) -> std::vector<int> {
  if (c) {
    return {1,2};
  } else {
    return {3, 4, 5};
  }
}

I could use a fixed size std::array of std::optional<int> but I would rather resort to a C++14 or c++11 solution.

Any help would be greatly appreciated.