Re: "virtual" not extended to derived classes by default?

From:

"Tom Widmer [VC++ MVP]" <tom_usenet@hotmail.com>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 31 Jan 2007 11:07:11 +0000

Message-ID:

<##Ml2fSRHHA.1036@TK2MSFTNGP03.phx.gbl>

MrAsm wrote:

BTW: I read that, when memory allocation fails with "new", VC++6 does
not throw std::bad_alloc, but it returns NULL instead.

Do you C++ experts confirm this?

It's true.

Moreover, would you suggest a trick to adjust this? Maybe is there a
way to redefine the behaviour of "new", so it can throw std::bad_alloc
on error (instead of non-standard returning NULL)?

I believe overriding operators new and delete works ok in VC6:

#include <cstddef>

void* operator new(std::size_t size)
{
   void* p = malloc(size);
   if (!p)
      throw std::bad_alloc();
   return p;
}

void* operator new[](std::size_t size)
{
   void* p = malloc(size);
   if (!p)
      throw std::bad_alloc();
   return p;
}

void operator delete(void* p)
{
   free(p);
}

void operator delete[](void* p)
{
   free(p);
}

However, note that with any OS using virtual memory, std::bad_alloc
isn't as useful as it might be, since you usually grind to a halt due to
page faults before you actually run out of memory (physical + pagefile).

Tom