Should You Pass by Const Reference or by Value in C ?

Why Pass by Const Reference Over Value?

When passing arguments to a void function, both passing by value and by const reference offer distinct advantages. Let's explore their respective merits.

Performance Considerations

Pass by value incurs the overhead of copying the parameter, while pass by const reference avoids this by using a reference to the original argument. In scenarios where the argument is large or copying it is expensive, pass by const reference optimizes performance.

Compiler Assumptions

When passing an argument by value, the compiler cannot assume that the source and destination objects do not refer to the same entity. This forces the compiler to perform additional checks to ensure data integrity. Conversely, pass by const reference ensures the passed argument is neither modified nor aliases any other variable, simplifying compiler optimizations.

Examples of Optimization and Caution

A classic example of where pass by const reference benefits optimization is in a function that compares two objects. The compiler can safely assume that the local, const-referenced copies will retain their values, even after external function calls. On the other hand, pass by value would require constant re-reading to account for potential changes.

However, note that passing a const reference does not guarantee immutability. Global state or classes that manipulate global state may still alter the referenced object. As such, pass by const reference should be employed when the semantics of references are pertinent or when potential aliasing would outweigh the cost of parameter copying.

The above is the detailed content of Should You Pass by Const Reference or by Value in C ?. For more information, please follow other related articles on the PHP Chinese website!