Re: Operator delete question

From:
"Francesco S. Carta" <entuland@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 9 Oct 2009 13:31:28 -0700 (PDT)
Message-ID:
<37fa7581-e9fe-46b3-b830-250cd9158dfb@k4g2000yqb.googlegroups.com>
On 9 Ott, 19:22, snapwink <snapw...@gmail.com> wrote:

I am running into this weird behavior with operator delete on an
embedded system, so I am wondering if this is standard C++ behavior or
is my compiler doing something wrong (RVCT 2.2 compiler). Appreciate
your patience as this is a long example:

static void * my_malloc (unsigned int numBytes)
{
  printf ("my malloc\n");
  return malloc(numBytes);

}

static void my_free (void *bufPtr)
{
  printf ("my free\n");
  free (bufPtr);

}

/* Interface I am trying to implement */
class ISocket
{
public:
  virtual void Release() = 0;
  virtual void TCPSockMethod() = 0;

};

/* The implementation design I have is thus:
 * All common methods are implemented in class Socket.
 * Function specific to TCP sockets are implemented in class
TCPSocket.
 * class Socket is still abstract, there are some methods
unimplemented there.
 */
class Socket : public ISocket
/* Dont ask about virtual inheritence :-(
 * Our embedded compiler does not support that. */
{
public:
  /* This does additional ref cnt management, removing for simplicity
*/
  virtual void Release () {printf ("Socket::Release\n"); delete this;}
  virtual void TCPSockMethod () = 0;

protected:
  Socket() {printf ("Socket: Ctor\n");}
  virtual ~Socket() {printf ("Socket: Dtor\n");}

};

/* TCPSocket is the concrete object. This one has overloaded new/
delete
 * operators to use my own memory management. */
class TCPSocket : public Socket
{
public:
  TCPSocket() {printf ("TCPSock: Ctor\n");}
  virtual ~TCPSocket() throw() {printf ("TCPSock: Dtor\n");}
  virtual void TCPSockMethod () {printf ("TCP Sock method\n");}
  static void* operator new (unsigned int num) {return my_malloc
(num);}
  static void operator delete (void *buf) {my_free(buf);}

};

int main()
{
  ISocket *pISock = static_cast <ISocket *> (new TCPSocket());
  pISock->Release();
  return 0;

}

Compiling with GCC and running this, I am getting the expected
results:
my malloc
Socket: Ctor
TCPSock: Ctor
Socket::Release
TCPSock: Dtor
Socket: Dtor
my free

However, compiling with my embedded compiler, I get different results:
after "Socket: Dtor", the global operator delete is getting called
(instead of the one I overloaded). I want to understand what does C++
standard say about this, or is this dependent on compilers?


Believe me this is all a bit over my head, nonetheless I wanted to
drop in.

Last thing first: the delete operator you have defined should be
called instead of the default one, that has to be a problem of your
embedded compiler. You might check if that compiler has a forum or a
newsgroup, and check whether that issue is already known.

(I'm not saying your question isn't on topic, you asked about the C++
standard, your question is on topic indeed, just suggesting a further
path to follow)

As an aside, I wonder if you can bring it all somewhat closer to C++
by using iostreams and the obvious replacements of malloc (the built-
in new and delete).

One thing that caught my eye is your override of new returning void* -
shouldn't that return TCPSocket*? If you were using 'new', you
wouldn't be in need of casting, but in that case, you wouldn't be in
need of overriding 'new' at all.

Sorry if this is all wrong, I openly admit that I'm not on firm
ground, I'm just taking the chance to check if I'm getting things
right - waiting for more knowledgeable input.

Cheers,
Francesco
--
 Francesco S. Carta, http://fscode.altervista.org
 First time here? Read the 'Welcome' and the 'FAQ'
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