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What Is A Null Pointer Dereference Error?

Editorial Staff
June 01, 2022

CWE-476 Null Pointer Dereference is a programming error that can occur when a program attempts to deference a null pointer. This can happen when the programmer mistakenly assumes that a pointer pointing to NULL is actually pointing to a valid object. If the program dereferences the null pointer, it can cause a segmentation fault or other undefined behavior, which can lead to a crash.

Null pointer dereferences are particularly common in C and C++ programs, since these languages do not automatically check for NULL pointers. As a result, it is important for programmers to be careful when handling pointers in these languages.

There are a few ways to avoid null pointer dereferences. One is to use a language that does not allow them, such as Java. Another is to always check pointers for NULL before dereferencing them. Finally, some languages (such as C++) provide special operators that can be used to automatically check for NULL pointers before dereferencing them. These operators can help reduce the risk of null pointer dereferences, but they are not foolproof.

Null pointer dereferences can be difficult to debug, since they can occur in code that appears to be correct. As a result, it is important to test programs thoroughly before releasing them. Additionally, tools such as valgrind can be used to detect null pointer dereferences at runtime.

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