Re: What's wrong with using return const reference
Subhransu wrote:
I read in one of the links that,
- Returning by const reference exposes the internal data structure (I
understood it to some extent that the returned reference could be
assumed to be a member variable as it has to live even after the
called function returns)
- It makes the API vulnerable for BC (Binary Compatibility) break!
Can someone please explain how? Also, I had a notion that it is better
to return by const reference as it will have some performance edge.
Returning by a const ref is dangerous from the possible intrusion point
of view, AIUI. Use a 'cosnt_cast' and you can change the object without
it even knowing it.
Return by a value and you protect your object because [in most cases]
there is no way to get from the value to the object that produced it.
BC breakage occurs when you need to change your internal structure and
that causes a change in the interface, whereas with returned value you
often can avoid the change in interface.
As to your performance question, yes, it might give an edge. Or it
might not. You need to measure and also need to see whether the
difference (if any) actually matters.
V
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