#include <memory>

class Cimpl;

class Cpimpl {
    std::auto_ptr<Cimpl> impl;
public:
    Cpimpl();
};

#include "classes.h"
#include <stdio.h>

class Cimpl {
public:
    Cimpl() {
        printf("Cimpl::Cimpl()n");
    }
    ~Cimpl() {
        printf("Cimpl::~Cimpl()n");
    }
};

Cpimpl::Cpimpl() {
    this->impl.reset(new Cimpl);
}

#include "classes.h"

int main() {
    Cpimpl c;
    return 0;
}

g++ -Wall -c main.cpp
g++ -Wall -c classes.cpp
g++ -Wall main.o classes.o -o app_bug
g++ -Wall classes.o main.o -o app_ok

struct Cimpl;

struct Cpimpl
{
    Cpimpl();
    ~Cpimpl();

    // other public methods here

private:
    Cimpl *ptr;

    // Cpimpl must be uncopyable or else make these copy the Cimpl
    Cpimpl(const Cpimpl&);
    Cpimpl& operator=(const Cpimpl&);
};

#include <stdio.h>

struct Cimpl
{
    Cimpl()
    {
        puts("Cimpl::Cimpl()");
    }
    ~Cimpl()
    {
        puts("Cimpl::~Cimpl()");
    }

    // etc
};

Cpimpl::Cpimpl() : ptr(new Cimpl) {}
Cpimpl::~Cpimpl() { delete ptr; }

// etc