C++ VALUE CATEGORY HIERARCHY:
Expressions
/ \
glvalue rvalue
/ \ / \
lvalue xvalue prvalue
(Identity, (Identity, (No Identity,
Not Movable) Movable) Movable Temporary)Logical AND (&&) and Logical OR (||) evaluate operands from left to right with guaranteed short-circuit evaluation: if the left operand determines the outcome, the right operand is never executed.
#include <iostream>
#include <string>
#include <utility>
void processValue(const std::string& lval) {
std::cout << "Lvalue bind: " << lval << "
";
}
void processValue(std::string&& rval) {
std::cout << "Rvalue / Move bind: " << rval << "
";
}
int main() {
std::string message = "Persistent lvalue";
processValue(message); // Calls lvalue overload
processValue("Temporary prvalue"); // Calls rvalue overload
processValue(std::move(message)); // std::move converts to xvalue -> rvalue overload
// Short-circuit evaluation demonstration
int* ptr = nullptr;
if (ptr != nullptr && *ptr == 10) {
// Safe: *ptr is never evaluated because left side is false
} else {
std::cout << "Short-circuit evaluation prevented null pointer dereference.
";
}
return 0;
}std::move to explicitly cast lvalues to xvalues when ownership transfer is intended.i = i++).