c++ nodiscard

The nodiscard attribute in C++ is used to indicate that a function's return value should not be ignored. It is a part of the C++17 standard and is primarily used for functions that have a specific purpose or side effect that should not be disregarded.

Here are the steps to use nodiscard in C++:

  1. Identify the function: Determine which function in your code needs to have its return value checked.

  2. Add the nodiscard attribute: Place the nodiscard attribute before the function declaration. This can be done in one of two ways:

a. Method 1: Add the nodiscard attribute before the function's return type, like this: [[nodiscard]] returnType functionName().

b. Method 2: Add the nodiscard attribute after the function's return type, like this: returnType functionName() [[nodiscard]].

  1. Compile the code: Save the changes and compile the code with a C++17-compliant compiler. This will ensure that the compiler enforces the nodiscard attribute and emits a warning if the return value of the function is ignored.

  2. Handle the warning: If the compiler generates a warning for ignoring the return value of the function, review the code and determine if the return value should indeed be used or if it can be safely ignored.

  3. Address the warning: If the return value is required, modify the code to utilize the return value appropriately. This may involve assigning the return value to a variable, using it in an expression, or passing it as an argument to another function.

By following these steps, you can effectively use the nodiscard attribute in C++ to ensure that the return value of a function is not ignored, thereby preventing potential bugs or unintended behavior.