Re: Temporaries, references, lifetimes and const_cast

"Victor Bazarov" <>
2 Jun 2006 18:53:23 -0400
Paul Thomas wrote:

I know this subject comes up a lot - and I've got the gist of it - but
there is one particular case that I can't work through. Is it legal
or not?

This has come up before:

std::string Func() { return "monkey"; }

int main()
   const std::string &cstr = Func();

   std::string &str = const_cast<std::string &>(cstr);

   str = "ape";

and the Jury seems to be out still.

Really? What for? It's allowed. Period.

But I want to do something even nastier:

#include <string>
#include <iostream>

std::string Func() { return "monkey"; }

std::string& Funky(std::string& str){
   return str += " magic";

std::string& Munky(const std::string& cstr){
   return const_cast<std::string &>(cstr);

int main(){
   //Funky(Func()); <-- no-no!
   std::cout << Funky(Munky(Func())) << std::endl;


I haven't had trouble compiling it, but why hasn't the constant
reference bound to the return from Func() gone out of scope when
Munky() returns?

It's an argument to 'Munky'. It lives until the full expression
that contains the function call is evaluated.

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