Lifetime issue when storing a `popo::Sample`

[mossmaurice]

Required information

Operating system: Any

Compiler version: Any

Observed result or behaviour:

Comes from this comment:

You have a livetime issue here. See this code:

SamplePointer<SampleType>&& acquireSample() {
 EventPublisher<Topic> publisher;
 return std::move(publisher.Loan());
}

int main() {
  auto sample = acquireSample();
}

In the end you can construct a lot of examples where the EventPublisher goes out of scope before SamplePointer does and then one has a problem. I think this is another problem with the automotive API where one has to state at least a big red warning that the EventPublisher has to live as least as long as the SamplePointer.

But just so that you are aware how bad this problem is, take a look at this evil bug:

class MyClass {
  SamplePointer<SampleType> m_sample; 
  EventPublisher<Topic> m_publisher;
}

This ordering of member variables is evil, when the MyClass destructor destroys the member it does it in inverse order, first the m_publisher and then the m_sample and one has again undefined behavior. I would bet in a code review no one would have seen this. There are a lot of bugs out there where applications cannot terminate cleanly and cause leaks or segfaults because of this issue.

Expected result or behaviour: Add a notification in each of the destructors like it is done for WaitSet and Listener.

Conditions where it occurred / Performed steps: See above

[elBoberido]

@mossmaurice this is a duplicate of #560 if I understand this correct