What does the error NULL Pointer Assignment means and what causes this error?

Answer 1

It means your computer has crashed and is caused by current microprocessor technology being in the early stages of development. Current experts expect this problem to disappear in about 10 - 25 years. Seriously many tens of thousands of things could have caused the problem in the first place - a single cause would be impossible to determine.

Answer 2

Null pointer assignment is a runtime error. It most often occurs when you attempt to assign a value to the NULL address (hence the name of the error) but it can also occur whenever you attempt to assign a value to an address that does not belong to your process. For example:

void f (int* p) {

*p = 42;

// ...

}

The above function is unsafe because it assumes ptr always refers to a valid address. As a result, the following will cause a null pointer assignment error:

f (NULL); // error!

Or, more subtly:

void g (int* p) {

f (p); // p could be valid, but it could also be NULL or even uninitialised!

// ...

}

To avoid null pointer assignments, always initialise your pointers with a valid address. If you have no suitable address to initialise with, initialise with the NULL address:

int* ptr = NULL;

Every time your code changes the address assigned to a pointer, the onus is upon your code to ensure the validity of that address. If done consistently, any code that assigns through a potentially NULL address can use a simple assertion:

void f (int* p) {

assert (p != NULL);

*p = 42;

// ...

}

In this way you can catch and eliminate null pointer assignments in debug builds (when NDEBUG is not defined) without paying the cost of runtime testing in release builds (when NDEBUG is defined).

Answer 3

Null pointer assignment means assigning a value to 0th location or accessing 0th location which is run time error should be avoided.

Answer 4

It means that you haven't initialized the pointer or the object it points does not exist any more or not accessible.