Can a C Reference Be Null?

Is Null Reference a Possibility?

In this code, a reference is declared and initialized to a value obtained from dereferencing a null pointer:

int &nullReference = *(int*)0;

While it may appear valid based on compiler behavior, it's essential to understand that references differ from pointers.

According to the C Standard (8.3.2/1):

"A reference shall be initialized to refer to a valid object or function... in particular, a null reference cannot exist in a well-defined program."

This emphasizes that a null reference, one that does not refer to any valid object, is not a well-defined concept within C .

Furthermore, the Standard (1.9/4) states that "the effect of dereferencing the null pointer" is undefined. In this case, where we have a reference initialized using a null pointer, it would mean dereferencing a null pointer itself, which is explicitly undefined behavior.

Therefore, while the code may compile without warnings, it is not valid C code and should be avoided. Null references are not a valid concept in the language, and any attempt to create one will result in undefined behavior.

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