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In some programming language environments (at least one proprietary Lisp implementation, for example), [citation needed] the value used as the null pointer (called nil in Lisp) may actually be a pointer to a block of internal data useful to the implementation (but not explicitly reachable from user programs), thus allowing the same register to be used as a useful constant and a quick way of ...
Null pointer dereference – A null pointer dereference will often cause an exception or program termination in most environments, but can cause corruption in operating system kernels or systems without memory protection or when use of the null pointer involves a large or negative offset.
To expose dangling pointer errors, one common programming technique is to set pointers to the null pointer or to an invalid address once the storage they point to has been released. When the null pointer is dereferenced (in most languages) the program will immediately terminate—there is no potential for data corruption or unpredictable behavior.
All loops must have fixed bounds. This prevents runaway code. Avoid heap memory allocation. Restrict functions to a single printed page. Use a minimum of two runtime assertions per function. Restrict the scope of data to the smallest possible. Check the return value of all non-void functions, or cast to void to indicate the return value is useless.
Dereferencing a null pointer in C produces undefined behavior, [7] which could be catastrophic. However, most implementations [citation needed] simply halt execution of the program in question, usually with a segmentation fault. However, initializing pointers unnecessarily could hinder program analysis, thereby hiding bugs.
Determining the root cause – debugging the bug – can be simple in some cases, where the program will consistently cause a segmentation fault (e.g., dereferencing a null pointer), while in other cases the bug can be difficult to reproduce and depend on memory allocation on each run (e.g., dereferencing a dangling pointer).
In computer programming, a reference is a value that enables a program to indirectly access a particular datum, such as a variable's value or a record, in the computer's memory or in some other storage device. The reference is said to refer to the datum, and accessing the datum is called dereferencing the reference. A reference is distinct from ...
Void safety (also known as null safety) is a guarantee within an object-oriented programming language that no object references will have null or void values. In object-oriented languages, access to objects is achieved through references (or, equivalently, pointers ).