How does the C++ function library handle errors?

Common error handling methods in C function libraries include exceptions and error codes. Exception handling is used to handle unexpected changes in program state, while error codes are numeric codes that represent error conditions. Handling exceptions requires the use of try-catch statements, while handling error codes requires checking the error code after the function call and taking action as necessary. Additionally, be sure to always use exception handling to handle unexpected events, use error codes to handle specific error conditions, and provide helpful error messages.

Error Handling in C Libraries: A Practical Guide

When developing C applications, handling errors is crucial. A robust library should be able to properly report and handle errors to ensure application stability.

Error handling types

Error handling in C function libraries is usually divided into two categories:

• Exception: Exception events can cause unexpected changes in program state and are typically raised via the throw keyword.
• Error code: Error code is a numerical code defined by the function library, indicating an error condition.

Exception handling

To handle exceptions, you need to use the following syntax:

try {
  // 可能引发异常的代码
} catch (const std::exception& e) {
  // 处理异常
}

Error code handling

To handle error codes, you need to use the following method:

int errCode = functionCall();
if (errCode != 0) {
  // 处理错误
}

Practical case

Consider the following example function, which opens a file:

File openFile(const std::string& filename) {
  try {
    return File{filename};
  } catch (const std::exception& e) {
    throw std::runtime_error("无法打开文件：" + filename);
  }
}

Call this function and print an error message if an error occurs:

int main() {
  try {
    File file1 = openFile("existing_file.txt");
    File file2 = openFile("non_existing_file.txt");
  } catch (const std::exception& e) {
    std::cerr << e.what() << std::endl; // 打印错误消息
  }
}

The above will print the following error message:

无法打开文件：non_existing_file.txt

Best Practice

When handling errors, follow these best practices:

• Always use exception handling to handle unexpected errors (such as memory allocation failures).
• Use error codes to handle library-specific error conditions.
• Provide clear and helpful error messages.
• Log serious errors (such as fatal exceptions).

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