c++ - How can I be sure a routine is taking advantage of (N)RVO? -

i'd make sure routines leveraging (n)rvo whenever possible. other parsing through resulting disassembly, there can or check see if routine being compiled (n)rvo? @ point i'm interested in msvc , gcc.

no, not really.

however can follow guidelines when writing code.

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unnamed return value optimization

this pretty triggered every time return temporary, in debug mode.

return myobject(....); 

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named return value optimization

this pretty triggered every time function return same temporary object:

myobject func() {   myobject result;   if (...) { return result; }    result.push(0);   return result; } 

you can mix those, becomes nigh impossible compiler apply rvo in case:

myobject func() {   myobject result;   if (...) { return myobject(...); }    return result; } 

here, 1 return benefit rvo , other not. , bet on first being optimized because you'd stuck if speculatively create result in return slot , need take if branch. note reordering statements work:

myobject func() {   if (...) { return myobject(...); }    myobject result;    return result; } 

so rule of thumb nrvo there should no return statement between declaration of result , return result; statement return else result itself.

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if follow this, stack odds in favor. , it's matter of code review.

and make code easier read since not declare variables before knowing need them!