Should You Null Pointers in Destructors? The Case Against and Why Alternatives are Better.

Is Nulling Pointers in Destructors Beneficial?

In C , it is common to dynamically allocate memory when creating objects. However, when those objects are destroyed, it is crucial to properly deallocate the memory. The destructor is responsible for this task. While it is essential to delete the allocated memory, the additional step of setting pointers to NULL in the destructor has been questioned.

Assumption vs. Reality

The assumption that setting the pointers to NULL is a waste of time in the provided code example has been challenged. This practice may be valuable in DEBUG builds for debugging purposes.

Why Setting to NULL Can be Harmful

Setting pointers to NULL in the destructor can potentially conceal problems in DEBUG builds that would otherwise be apparent in RELEASE builds. For example, if there is a dangling reference to a deleted object and the pointer is set to NULL, the code may avoid using the pointer due to the NULL check. This could result in a buggy code that still executes without user knowledge.

Alternatives to Nulling Pointers

Instead of setting pointers to NULL, it is better to establish a different idiom. One effective method is to set the pointer to a known bad pointer value. This way, if there is a dangling reference to the object, any attempt to use the pointer will result in a diagnosable crash. This helps catch the bug rather than masking it.

Conclusion

While nulling pointers in destructors may seem like a trivial task, it is crucial to understand its potential consequences. In general, it is not recommended to set pointers to NULL in destructors. Instead, consider using alternative approaches that provide clearer diagnostics and minimize debugging headaches.

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