Re: Temporaries, references, lifetimes and const_cast

From:

"Eugene Alterman" <eugalt@verizon.net>

Newsgroups:

comp.lang.c++.moderated

Date:

3 Jun 2006 07:49:14 -0400

Message-ID:

<xbMfg.6773$o%3.5514@trndny07>

"Paul Thomas" <pt@fightspam.com> wrote in message
news:447eb52f$0$98930$ed2619ec@ptn-nntp-reader01.plus.net...

[snip]

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;
}

</code>

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?

You seem to be puzzled by the fact that the temporary created by Func()
appears to be pretty much alive after the reference parameter of Munky() its
is bound to ceases to exist when Munky() exits.

You are forgetting that the temporary will not be destroyed until the full
expression - std::cout << Funky(Munky(Func())) << std::endl - has been
evaluated

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