Is Deleting a NULL Pointer Safe, and What Are the Best Coding Practices?

Deleting NULL Pointers: A Matter of Safety and Coding Style

When handling pointers, it's important to ensure their validity. One common question arises: is it safe to delete a NULL pointer?

Safety of Deleting NULL Pointers

Yes, it is safe to delete a NULL pointer. When the delete operator is invoked on a NULL pointer, it essentially does nothing. This is because the delete operation inherently checks if the pointer is NULL before attempting to deallocate the memory. Thus, explicitly checking for NULL pointers before deleting them is unnecessary and can introduce overhead.

Coding Style Considerations

While it's safe to delete NULL pointers, it's generally considered good coding practice to assign the pointer to NULL after deletion. This helps avoid double deletion, which is a common source of memory corruption errors.

For instance, consider the following code:

int* ptr = new int;
delete ptr;
delete ptr; // Double deletion error

By setting ptr to NULL after deletion, you can effectively prevent this issue:

int* ptr = new int;
delete ptr;
ptr = NULL;

Custom Implementation Using Macros

Some developers advocate for custom implementations that automatically set deleted pointers to NULL. For example, a macro like the following could be defined:

#define my_delete(x) {delete x; x = NULL;}

This macro would encapsulate both the deletion operation and the subsequent null assignment. However, it's worth noting that R and L values considerations apply when using this approach.

The above is the detailed content of Is Deleting a NULL Pointer Safe, and What Are the Best Coding Practices?. For more information, please follow other related articles on the PHP Chinese website!