c++ - Appropriate way to forward rvalue reference -

i have following code:

#include <iostream> #include <string>  using std::cout; using std::endl;  void bar(const std::string& str) {     cout << "const str - " << str << endl; }  void bar(std::string&& str) {     cout << "str - " << str << endl; }  void foo(std::string&& str) {     bar(str); }   int main() {     foo("hello world"); } 

in above code void bar(const std::string& str) overload gets called. if want void bar(std::string&& str) overload called either have write bar(std::move(str)); or bar(std::forward<std::string>(str));

obviously forward code longer, makes more sense me. question more commonly used , prefered. writing bar(std::forward(str)); best solution imo, not option :)

citing effective modern c++

from purely technical perspective, answer yes: std::forward can all. std::move isn’t necessary. of course, neither function necessary, because write casts everywhere, hope agree that be,well, yucky. std::move’s attractions convenience, reduced likelihood of error, , greater clarity.

using std::move here

void foo(std::string&& str) {     bar(str); } 

will return str rvalue reference (which you're trying achieve) while using std::forward return either lvalue reference (which you're not interested in) or rvalue reference (thus equivalent in case std::move). using none keep calling const std::string& str 1 since str lvalue in function.

bottom-line: same thing using std::move preferred since

• it avoids explicitly specifying template arguments
• it more idiomatic
• it goes straight point: std::forward not intended used way (cfr. universal references) or in context although surely work

i might agree "i'm forwarding rvalue reference other function" might make sense standalone sentence kind of misses point of matter. re-wire brain think "keep 'moving' rvalue reference other function"

also possibly related: https://stackoverflow.com/a/18214825/1938163