Can I use rvalue reference to temporary? Is it undefined behavior or not?

Question

Updating the question Why this two rvalue references examples have different behavior?:

Source code:

int a = 0;
auto && b = a++;
++a;
cout <&l         


        

Answer 1

Taking a reference to a temporary extends its lifetime to the end of lifetime of that reference.

ISO/IEC 14882 § 12.2/5:

The second context is when a reference is bound to a temporary. The temporary to which the reference is bound or the temporary that is the complete object of a subobject to which the reference is bound persists for the lifetime of the reference […]