如果每次new出来 ，都要判断是否成功（地址是否为空），那么也挺麻烦的。c++提供set_new_handler，当new失败时，会调用set_new_handler设置的回调函数。
function
std::set_new_handler
<new>
new_handler set_new_handler (new_handler new_p) throw();
Set new handler function
Sets new_p as the new handler function.The new handler function is the function that is called by functions operator new or operator new[] when they are not successful in an attempt to allocate memory.
The new handler function can make more storage available for a new attempt to allocate the storage. If, and only if, the function succeeds in making more storage avaible, it may return. Otherwise it shall either throw a bad_allocexception (or a derived class) or terminate the program with cstdlib's abort or exit functions.
If the new handler function returns (i.e., it made more storage available), it can be called again if the operator newor operator new[] function is again not successful attempting to allocate the storage. This may repeat itself until either the allocation is successful or the handler function fails.
Parameters
- new_p
- Function that takes no parameters and returns void.
The function can make more storage available or throw an exception or terminate the program.
new_handler is a function pointer type taking no parameters and returning void.
Return value
The value of the current new_handler function if this has been previously set by this function, or a null pointer if this is the first call to set_new_handler.new_handler is a function pointer type taking no parameters and returning void.