Using ternary operator to initialize a reference variable?

Question

Putting all the maintainability and reading issues aside, can these lines of code generate undefined behavior?

float  a = 0, b = 0;
float& x = some_condition()? a : b;
x = 5;
cout << a << ", " << b;

Answer 1

No, it's just fine. It would not create undefined behavior in this code. You will just change value of a or b to 5, according to condition.

Answer 2

This is absolutely fine, as long as both sides of the conditional are expressions that can be used to initialize a reference (e.g. variables, pointer dereferences, etc)

float& x = some_condition()? a : *(&b); // This is OK - it is the same as your code
float& x = some_condition()? a : b+1;   // This will not compile, because you cannot take reference of b+1