1.1.3.4 new_handler

• The new-handler function is the function called by allocation functions whenever a memory allocation attempt fails. Its intended purpose is one of three things:
  1. make more memory available. ( resolve myself)
  2. throw exception of type std::bad_alloc or derived from std::bad_alloc. (resolve by user)
  3. terminate the program. e.g. by calling std::terminate. (No resolve)
• At program startup, new-handler is a null pointer. allocation function finds that std::get_new_handler returns a null pointer value, it will throw std::bad_alloc.
• The default implementation throws std::bad_alloc. The user can install his own new-handler, which may offer behavior different than the default one.
• If new-handler returns, the allocation function repeats the previously-failed allocation attempt and calls the new-handler again if the allocation fails again. To end the loop, new-handler may call std::set_new_handler(nullptr).
• Use set_new_handler function. When memory allocate failed, it will call this "callback" function.
  void noMemory(){ 
  closeIE; // method 1 release mem 
  set_new_handler(nullptr); //mehtod 2 throw bad_alloc exception. 
  abort();  //method 3, end application. 
  } 
  //in the beginning of main() function. 
  set_new_handler(noMemory)

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