Re: What is wrong with this reference?

Victor Bazarov <>
Thu, 29 Jan 2009 08:53:10 -0500
Michael wrote:

This is the sample program:


int main()
        int*const a=new int;
        const int*const&b=a;
        printf("%p %p\n",&a,&b);
        delete a;
        return 0;

When running, it produces:

0x7fff1dc49fc8 0x7fff1dc49fb8

You sound surprised. A reference is initialised with an rvalue obtained
apparently from copying the original ('a'). So, it refers to some other
object, a temporary.

That means the memory locations of a and b are different i.e. a and b is
different object!


 > I want to make something that *a is modifiable but *b is

not (to be used inside a class) but the following code generates a
compile-time error:


int main()
        int*a=new int;
        const int*&b=a;
        printf("%p %p\n",&a,&b);
        delete a;
        return 0;

test.cpp:6: error: invalid initialization of reference of type ???const int*&???
from expression of type ???int*???

I am not sure why this is, to be honest with you. Those indirect const
qualifiers always confuse me.

The following code runs perfect:

Define "perfect", please.


int main()
        int a=new int;

Huh? What language is that? Java? This should be a compilation error.

        const int&b=a;
        printf("%p %p\n",&a,&b);
        return 0;

What is the problem in the first code (I am using g++ 4.2.4)?

Problem? I don't see any problem.

struct A { int a; };

int main() {
     A* pNormalA = new A;
     pNormalA->a = 42; // hey, it's modifiable

     A const* pConstA = pNormalA;
     pConstA->a = 666; // error, not modifiable

Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

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