[otabdeveloper2]

> Many of those are ruled out as modern successors (in my mind, at least), when they continue to make “the billion dollar mistake” (to use its inventor’s own words[1]) of null references.

Well, you're in luck then! You don't even need a 'modern' successor, C++ (even the ancient versions) disallow null references.

[masklinn]

> Well, you're in luck then! You don't even need a 'modern' successor, C++ (even the ancient versions) disallow null references.

That's useful, until you realise that all its smart pointers are semantically nullable (they can all be empty with the same result as a null raw pointer) and then nothing's actually fixed.

[Mesopropithecus]

What you mean is that C++ doesn't have a way to (easily) let you check whether a given reference is null or not. int* a = NULL; int& b = *a; compiles and runs just fine.

[masklinn]

> compiles and runs just fine.

For fairly low values of those. Creating a null reference is UB, your program is not legal at all.

[coldtea]

If the compiler still accepts it, then that it belongs to the "UB" class of code is not much comfort.

The whole point is to NOT have it be accepted.

[jessaustin]

Sure, we're not supposed to do that. Sometimes it happens anyway, and the C++ compiler isn't much help in that case.

[ethan_g]

No the gp is correct, references in c++ can't be null. Your code invoked undefined behavior before you did anything with a reference, namely *a which is a null pointer dereference.

[the_why_of_y]

> namely *a which is a null pointer dereference.

Which is a textbook example of the null reference problem.

Edit: There may be some terminological confusion here: when programming language folks talk about "references", they include in that definition what C/C++ call "pointers". See for example the Wikipedia article, which gives as the C++ example not C++ references, but C++ pointers.

https://en.wikipedia.org/wiki/Reference_(computer_science)

[mdpopescu]

The "null problem" is that a static language does a run-time check instead of a compile-time check. By the time the undefined behavior is invoked, compilation ended.

[coldtea]

>Your code invoked undefined behavior before you did anything with a reference

Since nobody stopped you, the problem is still there.