Re: Ideas for strong guarantee?

David Abrahams wrote:


If I had one more vector the source code would grow up considerably
For example:
void func()
    {
       std::auto_ptr<Type> sp1(new Type());
       std::auto_ptr<Type> sp2(new Type());
       std::auto_ptr<Type> sp3(new Type());

       m_vec1.push_back(sp1.get());
       try
       {
          m_vec2.push_back(sp2.get());
       }
       catch(...)
       {
          m_vec1.pop_back();
          throw;
       }

       try
       {
          m_vec3.push_back(sp3.get());
       }
       catch(...)
       {
          m_vec1.pop_back();
          m_vec2.pop_back();
          throw;
       }

       sp1.release();
       sp2.release();
       sp3.release();
    }

Mybe an alternative is provide a "undo" operation in local class
descructor.
For example:

struct undo_push_back
{
     typedef std::vector<Type*> containerType;
     containerType m_vec;
     bool m_bReleased;
     undo_push_back(containerType & vec) : m_vec(vec),
m_bReleased(false) {}
     ~undo_push_back(containerType & vec)
     {
         if (!m_bReleased)
         {
             m_vec.pop_back();
         }
     }
     void release()
     {
         m_bReleased = true;
     }
};

   void func()
    {
       std::auto_ptr<Type> sp1(new Type());
       std::auto_ptr<Type> sp2(new Type());
       std::auto_ptr<Type> sp3(new Type());

       m_vec1.push_back(sp1.get());
       undo_push_back undo1(m_vec1);

       m_vec2.push_back(sp2.get());
       undo_push_back undo2(m_vec2);

       m_vec3.push_back(sp3.get());

       undo1.release();
       undo2.release();
       sp1.release();
       sp2.release();
       sp3.release();
    }

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