C++ return by reference: evaluate the two claims We can return a global variable by reference. 2) We cannot return a local variable by reference.

Introduction / Context:
Returning by reference can avoid copies and enable idioms like chaining assignments. However, a returned reference must remain valid after the function returns. Understanding object lifetime is essential to decide which references are safe to return from a function.

Given Data / Assumptions:

• Global (or static storage duration) variables outlive function calls.
• Local automatic variables are destroyed when a function returns.
• We discuss references to non-temporary objects.

Concept / Approach:

A function may safely return a reference to an object that continues to exist after the function ends, such as a global or static variable, because the reference remains bound to a live object. Conversely, a reference to a local automatic variable becomes dangling as soon as the function returns, leading to undefined behavior. Therefore, returning a global by reference is acceptable, while returning a local by reference is not.

Step-by-Step Solution:

Verification / Alternative check:

Returning a reference to a static local is also permissible because it persists across calls. Compilers with warnings enabled will often flag returning a reference to a local automatic variable as a dangerous error pattern.

Why Other Options Are Wrong:

Only 1 or only 2: ignores the validity of the other correct statement.

Both incorrect: contradicts standard lifetime rules.

Common Pitfalls:

• Accidentally returning references to temporaries (e.g., the result of an expression), which also dangle.
• Misunderstanding that returning by value is often safer and optimized via copy elision or move semantics.

Final Answer:

Both 1 and 2 are correct.