Is null reference possible?

References are not pointers.

8.3.2/1:

A reference shall be initialized to refer to a valid object or function. [Note: in particular, a null reference cannot exist in a well-defined program, because the only way to create such a reference would be to bind it to the “object” obtained by dereferencing a null pointer, which causes undefined behavior. As described in 9.6, a reference cannot be bound directly to a bit-field. ]

1.9/4:

Certain other operations are described in this International Standard as undefined (for example, the effect of dereferencing the null pointer)

As Johannes says in a deleted answer, there’s some doubt whether “dereferencing a null pointer” should be categorically stated to be undefined behavior. But this isn’t one of the cases that raise doubts, since a null pointer certainly does not point to a “valid object or function”, and there is no desire within the standards committee to introduce null references.

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