Re: Exception caught inside a constructor

From:

Casey <cartec69@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 11 Jul 2013 09:38:03 -0700 (PDT)

Message-ID:

<3a4e38bc-a087-42d7-b371-2e1c54a2422f@googlegroups.com>

On Tuesday, July 9, 2013 9:33:38 AM UTC-5, Jarek Blakarz wrote:

The following program throws an exception while allocating "A" object.
Please help me to modify the program to work correctly. I want all exceptions
to be caught inside a "C" constructor and no memory leak should happen.

Use smart pointers. Failing that:

#include <iostream>

using namespace std;

struct A {
  A(void)
  {
    cout << "A" << endl;
  }

  ~A(void)
  {
    cout << "~A" << endl;
  }

  void* operator new(size_t size)
  {
    cout << "A new" << endl;
    throw 10; // allocation fails
    return ::operator new(size);
  }
};

struct B {
  B(void)
  {
    cout << "B" << endl;
  }

  ~B(void)
  {
    cout << "~B" << endl;
  }
};

struct C {
  B *ptrB;
  A *ptrA;

  C(void)
  {
    cout << "C" << endl;
    try {
      ptrB = new B;
    } catch(...) {
      cout << "new B - exception" << endl;
      throw;
    }
    try {
      ptrA = new A;
    } catch(...) {
      cout << "new A - exception" << endl;
      delete ptrB;
      throw;
    }
  }

  ~C(void) {
    cout << "~C" << endl;
    delete ptrB;
    delete ptrA;
  }
};

int main(void)
{
  try {
    C c;
  } catch(...) {
    cout << "main exception handler" << endl;
  }
}