Re: MSVC 2003: ctor-try-block error: possible compiler bug

From:
Ulrich Eckhardt <eckhardt@satorlaser.com>
Newsgroups:
comp.lang.c++.moderated
Date:
27 Sep 2006 13:52:41 -0400
Message-ID:
<uviqu3-msj.ln1@satorlaser.homedns.org>
Kirill Sukhonosenko wrote:

struct IRefCounted
{
virtual void addRef() = 0;
virtual void release() = 0;

virtual ~IRefCounted() {};

                           ^ unnecessary

};

struct ILogger : public IRefCounted
{
void virtual write(const char * text) = 0;
};


Why force implementors of ILogger to also implement IRefCounted? C++ has
multiple inheritance! In fact, I'd rather have made IRefCounted a concrete
class with a concrete implementation that invokes "delete this;" - a
virtual dtor will do the right thing!

template<typename T>
class CountingPtr
{
T * m_t;

public:
CountingPtr(T * t, bool addRef = true) : m_t(t)
{
  assert(t!=0);
  if(addRef)
    t->addRef();
}

~CountingPtr()
{
  if(m_t)
    m_t->release();
}


Hmmm, weird. In the ctor, you assert() that m_t is not null and here you
check it again?

CountingPtr&operator=(const CountingPtr & rhs)
{
  if(this == &rhs)
    assert(false);
  else
  {
    m_t = rhs.m_t;
    m_t->addRef();
  }
  return *this;
}


This is very nontypical. Firstly, self-assignment, even though it rarely has
a proper use, can much easier be handled gracefully without asserting:

  if(this!=&rhs)
  { ...do assignment... }
  return *this;

Else, you simply overwrite the current value of m_t without first
deregistering from it (using release()). This is almost certainly wrong!

CountingPtr(const CountingPtr & rhs)
{
  *this = rhs;
}


Note that here, you will also have to init m_t to zero before doing the
assignment!

Lastly, I'm missing a default ctor. The one generated by the compiler will
surely not do what you want, in particular not init m_t to zero.

I'm sorry if this doesn't directly address your problem, but browsing the
code those were some obvious mistakes I found and that I'd fix first. I
guess the rest will only turn out to be results of that.

Uli

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