Re: [boost] safe_dereference()

From: David Abrahams (dave_at_[hidden])
Date: 2002-09-04 15:37:04

From: "Bryan Ross" <bross_at_[hidden]>

> I may not be understanding something here, but are you saying that the
> following code won't work?
> 
> #include <iostream>
> #include <string>
> using namespace std;
> struct hold
> {
> hold(const int& i) : x(i) {}
> const int& x;
> };
> int f()
> {
> return 3;
> }
> int main(int argc,char** argv)
> {
> hold* h = new hold(f());
> cout << h->x << endl;
> delete h;
> return 0;
> }

Try spaces instead of tabs next time.

> This compiles and outputs '3', as expected. 

Pure luck. Try this instead:

#include <iostream>
#include <string>

static int cnt = 42;

struct X {
    X() : x(cnt++) { std::cout << "X(): " << x <<std::endl;}
    ~X() { std::cout << "~X(): " << x <<std::endl; x = -666; }
    int x;
};

using namespace std;
struct hold
{
    hold(const X& i) : x(i) {}
    const X& x;
};

X f()
{
    return X();
}

int main(int argc,char** argv)
{
    hold* h = new hold(f());
    cout << h->x.x << endl;
    delete h;
    return 0;
}

-----------------------------------------------------------
           David Abrahams * Boost Consulting
dave_at_[hidden] * http://www.boost-consulting.com