Re: Constness of return-by-value temporaries

From:

johnchx2@yahoo.com

Newsgroups:

comp.std.c++

Date:

Mon, 8 May 2006 22:08:51 CST

Message-ID:

<1147105991.825020.94980@y43g2000cwc.googlegroups.com>

Tom1s wrote:

(I'll admit that I'm not certain if ALL temporaries are non-const throughout
the entire language. Could someone please clarify that?)

It depends on the function type. In this example, the return value of
g() is const, while the return value h() is non-const:

   struct foo { void f() {} };

   const foo g() { return foo(); }
   foo h() { return foo(); }

   int main ()
   {
      g().f(); // error: return value of g() is const
      h().f();
   }

I have a question, which I have asked on comp.lang.c++, but which no-one has
seemed willing to answer. Is the following translation unit well-formed, and
absent of undefined behaviour?

#include <string>
using std::string;

#include <vector>
using std::vector;

vector<string> Func()
{
    vector<string> vec;

    vec.push_back("One");
    vec.push_back("Two");

    return vec;
}

#include <iostream>
using std::cout; using std::endl;

int main()
{
    const vector<string> &cvec = Func();

    vector<string> &vec = const_cast< vector<string>& >(cvec);

    vec.push_back("Three");

    cout << vec.at(0) << endl
         << vec.at(1) << endl
         << vec.at(2) << endl;
}

I don't see any problem with it.

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