Best Practices for Ignoring Function Return Values in C

C, being a powerful and versatile programming language, often requires developers to carefully manage function return values. However, in certain scenarios, ignoring return values can be both necessary and efficient. This article provides an in-depth look at how and when to ignore function return values in C, with a focus on best practices and avoiding compiler warnings.

Introduction to Ignoring Return Values

In C, if a function returns a value, that value can be assigned to a variable or simply ignored. Ignoring a return value can be beneficial in cases where the value is not required, such as error handling functions. However, failing to use the return value can lead to compiler warnings. To avoid these warnings, you can either cast the return value to void or simply ignore the return value without assigning it to a variable.

Examples of Ignoring Return Values

Example 1: Ignoring a Function Return Value

include stdio.h
int someFunction() {
    return 42; // Example return value
}
int main() {
    someFunction(); // Ignoring the return value
    return 0;
}

In this example, someFunction() returns a value, but it is not used in the main function. Simply calling the function and ignoring its return value is a straightforward approach.

Example 2: Casting to void

include stdio.h
int someFunction() {
    return 42; // Example return value
}
int main() {
    (void)someFunction(); // Explicitly ignoring the return value
    return 0;
}

By casting the return value to void, you explicitly tell the compiler that the return value is being intentionally ignored, which can help prevent warnings. This method is often considered better practice, especially in situations where the return value may be important for error handling.

Historical Context and Best Practices

Historically, functions in C are designed to return a value, even if it is not used. This is because the default return type for a function is int. Even if the function is declared as void, it still returns a value—a 0, often placed in a disposable register. This implies that even void functions must have a return value.

Ignoring the return value can be practical in many situations. For instance, in cases where the return value is not needed, such as when using functions from the C standard library (like printf), you can simply call the function without using its return value. However, it is generally advisable to assign the return value in cases where it might be needed for error checking or further processing.

For example:

int result  doAThing(); // Assigning the return value for error checking

Alternatively:

doAThing(); // Ignoring the return value if not needed

Conclusion and Recommendations

While ignoring function return values can be a useful technique, it is crucial to balance it with best practices. Using the void cast to silence compiler warnings is often recommended. However, you should always be aware of the potential need to use the return value for error handling or further processing.

Overall, the key is to use your judgment and consider the context of the function and the needs of your code. By doing so, you can write more efficient and error-free C code.

Keywords: C programming, return value, function call, compiler warnings, error handling