letting new operator return NULL;

Hi Folks...

how can I make the new-operator return null, if something fatal in the constructor happens?

Greets
Seb

beaver,

I do not fully understand the question. Perhaps the nothrow version of the operator new would be useful.

Sincerely, Chris.

Code:

---


#include <iostream>
#include <memory>

class c
{
private:

  unsigned char* pb;
  int            some_member;

public:

  c()
  {
    // Returns 0 if allocation fails.
    pb = new (::std::nothrow) unsigned char[1024 * 1024];

    if(!pb)
    {
      return;
    }

    some_member = 0;
  }

  ~c()
  {
    if(pb)
    {
      delete [] pb;
    }
  }

public:

  const bool valid(void) const { return pb != NULL; }

};

int main(int argc, char* argv[])
{
  c C;

  ::std::cout << (C.valid() ? 1 : 0) << ::std::endl;

  return 1;
}

---

Returning null from an allocator is an old C style. C++ was designed to work with exeptions. On this case you use CMemoryExeption, for example:

...
try
{
CString MyString = new CString;
}
catch(CMemoryException* e)
{
deal with the error here, you can see the structure e to pick the exact reason of the error
}
....

Override the new Operator

Code:

---

inline void* operator new( unsigned int size )
{
    return NULL;
}

---

cu