Dereferencing NULL Pointers for References in C

When dealing with pointers and references in C , it is important to understand the consequences of dereferencing a NULL pointer. In this context, "dereferencing" refers to the process of obtaining the value stored at the memory address pointed to by the pointer.

In the provided code snippet:

int* ptr = NULL;
int& ref = *ptr;
int* ptr2 = &ref;

the line "int& ref = *ptr" appears to dereference the NULL pointer "ptr" to obtain a reference. However, this behavior is undefined in the C standard.

According to the C standard (8.3.2/4 "References"), creating a NULL reference is undefined because it would involve dereferencing a NULL pointer. This action constitutes undefined behavior as stated in the standard.

It is crucial to remember that dereferencing a NULL pointer can lead to unexpected results and program crashes, so it should always be avoided. One exception to this rule is when using the "sizeof" operator, where the operand to "sizeof" is not actually evaluated, so the dereference never occurs.