How to set the return value attribute of a C++ function

By using the [[nodiscard]] attribute, we can instruct the compiler to force the use of the function's return value, otherwise a warning will be generated. Syntax: Add the [[nodiscard]] attribute to the function declaration or definition. Practical example: Adding the [[nodiscard]] attribute eliminates compiler warnings about unused return values. Recommendation: Use the [[nodiscard]] attribute when including important information, generating error messages, or returning pointers or references to improve code readability and safety.

How to set the return value attribute of a C function

In C, we can use[[nodiscard]] attribute to instruct the compiler that the return value of the function should be used, otherwise a warning will be generated.

Syntax

[[nodiscard]] Attributes can be added to a function declaration or definition:

• Function declaration:

  [[nodiscard]] int get_value();

• Function definition:

  int [[nodiscard]] get_value() {
      return 42;
  }

Actual combat Case

Consider the following code:

int get_value() {
    return 42;
}

int main() {
    // 如果不使用返回值，编译器将发出警告
    get_value();
}

The compiler will generate the following warning:

warning: unused variable 'result' [-Wunused-variable]

To eliminate the warning, you can on the get_value function Added [[nodiscard]] attribute:

[[nodiscard]] int get_value() {
    return 42;
}

Now the compiler will no longer issue a warning.

Instructions

Here are some suggestions for using the [[nodiscard]] attribute:

• Include Use it on the return value of important information.
• Use this when generating error messages or exceptions.
• Use this when returning a pointer or reference to avoid dangling pointers or references.

By using the [[nodiscard]] attribute, you can improve the readability and security of your code and avoid accidentally omitting important return values.

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