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POMemory footprint of C++ functions returning by reference or value?
 

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    <p>I am trying to reduce the memory footprint of an application developed mostly in C++ and one the things I was looking into was returning a particularly large data structure by reference vs returning them by value. I needed some confirmation on it. For instance, say I have member functions in a class <code>some_object</code> as follows: </p> <pre><code>const some_type&amp; get_some_type(...) { ...; return ...; } </code></pre> <p>vs </p> <pre><code>const some_type get_some_type(...) { ...; return ...; } </code></pre> <p>Is my understanding correct that assignment by calling the latter (return by value) would leave two copies of the data <code>some_type</code> in memory at certain points during the application's execution, while calling the former (return by reference) avoids this? </p> <p>Another effort as part of the overall goal of reducing the memory footprint was to change the very definition of <code>some_type</code> in a manner that would preclude using the return by reference option above. In such a case, since <code>some_type</code> (which is actually a container of sorts, say, of data of type <code>data_type</code>) is used inside a loop as follows: </p> <pre><code>const some_type&amp; = some_object-&gt;get_some_type(); // returns by ref. a large container for(...) { ...; data_type = some_type.at(...); ...; } </code></pre> <p>I assume if we are constrained to use the return by value above, then I would need to make the change as follows by introducing a new function <code>get_some_type_at</code> to get an element of the container by value (are there any downsides to doing this that I should be aware of, say, in performance?):</p> <pre><code>for(...) { ...; data_type = some_object-&gt;get_some_type_at(...); // returns by value a small object ...; } </code></pre> <p>Again I am looking mostly for confirmation of these aspects. But details and insights are most appreciated. Thanks for your time and interest!</p>
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