Here are some title options based on the content, formatted as questions: * Why Can Rvalues Be Passed by Const Reference but Not Non-Const Reference in C ? * C Rvalue References: When is Passing

Rvalue Reference Passing with Const and Non-Const References

In C , passing rvalues by const reference is permissible while doing so with non-const references raises errors. Consider the following code snippet:

<code class="cpp">void display(const int& a) {
    cout << a;
}</code>

This code will compile successfully and work correctly when called with an rvalue, such as a literal:

<code class="cpp">display(5); // OK</code>

However, if the const were removed from the reference parameter:

<code class="cpp">void display(int& a) {
    cout << a;
}</code>

Calling this function with an rvalue will result in a compilation error. This raises the question: why is passing rvalues by const reference allowed, but not by non-const reference?

Prolonging Temporary Variable Lifetime

The answer lies in how C handles temporary values created as a result of expressions. When an rvalue is used, a temporary object is created to hold its value. Normally, such temporary objects are destroyed immediately after their use. However, when bound to a const reference, they are granted an extended lifetime until the end of the containing scope.

Benefits of Const References

Using const references to pass rvalues offers the following benefits:

• Performance Enhancement: It avoids the need for unnecessary copy construction, resulting in better performance.
• Object Lifetime Control: Const references ensure that the temporary object remains valid until the function ends, preventing dangling references.
• Type Safety: Const references maintain the const-correctness of the code, preventing accidental modification of the rvalue.

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