Lifetime extension and the conditional operator

Question

local lvalue references-to-const and rvalue references can extend the lifetime of temporaries:

const std::string& a = std::string(\"hello\");
std::string         


        

Answer 1

std::string d = "hello";
const std::string& e = condition ? d : std::string("world");

Does C++ mandate the lifetime of the temporary be extended when the condition is false?

It will be. The conditional is an rvalue expression, and when bound with a const reference the compiler will create an unnamed object and bind the reference to it. What I am not 100% sure is whether the temporary whose lifetime is extended is std::string("world") or whether a copy of it is (conceptually) made (and elided).