Null-pointer dereferences, while common, can generally be found and corrected in a simple way. They will always result in the crash of the process, unless exception handling on some platforms is invoked, and even then, little can be done to salvage the process.
Null-pointer dereference issues can occur through a number of flaws, including race conditions and simple programming omissions. Improve this question. Ash Ash Keep in mind doing so results in undefined behavior. You might want to put down some example code. It seems that people including me don't get what you are trying to ask. No need for code there isn't any - This is a conceptual problem I am having, trying to get my head around the terminology of "dereferencing" and why I should be caring about it.
Thanks for this question. It's been bothering me for a while, to ask this : — William Martens. Add a comment. Active Oldest Votes. Improve this answer. Greg Hewgill Greg Hewgill k gold badges silver badges bronze badges. Ash: A pointer contains a memory address that references to something.
To access that something referenced by that memory address, you have to de-reference the memory address. Ash, which In silico said, but when you de-reference you getting the value that is stored at the memory address.
Give it a try. I think it's important to also state that it's undefined behavior, assuming that Adam Rosenfield's answer is correct.
Show 1 more comment. Adam Rosenfield Adam Rosenfield k 95 95 gold badges silver badges bronze badges. Actually, a NULL pointer does sometimes point to valid data. Lie Ryan Lie Ryan From wiki A null pointer has a reserved value, often but not necessarily the value zero, indicating that it refers to no object.. Prasoon Saurav Prasoon Saurav Thanks for your answer, I am ok with what a NULL pointer was, I just wasn't sure about how the "dereferencing" fits into the scheme of things. I didn't know that program crashes go " Whooosh!!!!
Quoting from wikipedia : A pointer references a location in memory, and obtaining the value at the location a pointer refers to is known as dereferencing the pointer. The null annotation may be used in a type definition to indicate that all instances of the type may be NULL.
For declarations of a type declared using null , the null annotation in the type definition may be overridden with notnull.
This is particularly useful for parameters to hidden static operations of abstract types see Section 4. For an abstract type, notnull may not be used for parameters to external functions, since clients should not be aware of when the concrete representation may by NULL. Parameters to static functions in the implementation module, however, may be declared using notnull , since they may only be called from places where the representation is accessible.
Return values for static or external functions may be declared using notnull. An additional annotation, relnull may be used to relax null checking. No error is reported when a relnull value is dereferenced, or when a possibly null value is assigned to an identifier declared using relnull. This is generally used for structure fields that may or may not be null depending on some other constraint. Splint does not report and error when NULL is assigned to a relnull reference, or when a relnull reference is dereferenced.
It is up to the programmer to ensure that this constraint is satisfied before the pointer is dereferenced. Splint - Secure Programming Lint. Manual Contents - Other Formats.
Null Checking Output from running Splint is displayed in sans-serif font. Splint Manual. Operation - 2. Null Dereferences - 3. Undefined Values - 4. Types - 5. Memory Management - 6.
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