/technologies/code_exchange/b/blog/posts/c-moving-and-returning-objects-part-2-move-and-copy---rule-of-sixIn object oriented designs, there are times when you replace an object by another. Example: when you store an object into an STL container. In a lot of those cases, you create an object, and add it. The object in the container is a cop...en-USTelligent Community 12https://community.element14.com/technologies/code_exchange/b/blog/posts/c-moving-and-returning-objects-part-2-move-and-copy---rule-of-sixTue, 13 Jan 2026 18:35:39 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:570ab178-4dbe-44b2-b7b2-c9077c66a62cJan Cumps0<p>I used <a href="https://en.wikipedia.org/wiki/Copy_elision#Summary" rel="noopener noreferrer nofollow" target="_blank" data-e14adj="t">wikipedia&#39;s test case</a> to check if C++ actually&nbsp;manages to allocate an object, created in a function, directly in its final memory location: yes</p> <p>[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:57e0d5ac-8dfb-48ce-add2-d3b2be1c8345:type=csharp&text=%23include%20%3Ciostream%3E%0D%0A%0D%0Astruct%20MyStruct%20%7B%0D%0A%20%20%20%20MyStruct%28%29%20%3D%20default%3B%0D%0A%20%20%20%20MyStruct%28%5B%5Bmaybe_unused%5D%5D%20const%20MyStruct%26%20x%29%20%7B%0D%0A%20%20%20%20%20%20%20%20std%3A%3Acout%20%3C%3C%20%28%22A%20copy%20was%20made.%5Cn%22%29%3B%20%7D%0D%0A%7D%3B%0D%0A%0D%0AMyStruct%20f%28%29%20%7B%0D%0A%20%20%20%20return%20MyStruct%28%29%3B%0D%0A%7D%0D%0A%0D%0AMyStruct%20f_named%28%29%20%7B%0D%0A%20%20%20%20MyStruct%20m%3B%0D%0A%20%20%20%20return%20m%3B%0D%0A%7D%0D%0A%0D%0Aint%20main%28%29%20%7B%0D%0A%20%20%20%20std%3A%3Acout%20%3C%3C%20%28%22Hello%20World%21%5Cn%22%29%3B%0D%0A%20%20%20%20MyStruct%20obj%20%3D%20f%28%29%3B%0D%0A%20%20%20%20MyStruct%20obj2%20%3D%20f_named%28%29%3B%0D%0A%7D]</p> <p>obj and obj2 are 2 MyStruct objects.&nbsp;Even though they are created inside functions ( f() and f_named() ), there is no copying when these 2 functions exit.<br />They actually construct the object in the memory that&#39;s allocated in main directly.</p> <p>C++ knows that the function&nbsp;return values are temporary and not used after the function exits.<br />So instead of creating a temporary object, and using a copy into obj or obj2 at return, it directly does the work in the&nbsp;destination object.</p> <p>result: using a function to&nbsp;factor an object comes without any runtime cost.</p> <p><img height="598" src="/resized-image/__size/1000x1196/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-570ab178-4dbe-44b2-b7b2-c9077c66a62c/pastedimage1768329465932v1.png" width="500" alt=" " /></p> <div> <div><span></span></div> <div><span></span></div> <div><span></span></div> </div><img src="https://community.element14.com/aggbug?PostID=29083&AppID=74&AppType=Weblog&ContentType=0" width="1" height="1">https://community.element14.com/technologies/code_exchange/b/blog/posts/c-moving-and-returning-objects-part-2-move-and-copy---rule-of-sixTue, 22 Jul 2025 19:07:33 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:570ab178-4dbe-44b2-b7b2-c9077c66a62cDAB0<p>Nice post Jan.</p><img src="https://community.element14.com/aggbug?PostID=29083&AppID=74&AppType=Weblog&ContentType=0" width="1" height="1">