What are the alternatives to exception handling in C++ functions?

In C, alternatives to exception handling provide several options for handling errors: Error codes: Use predefined codes to represent error conditions, making it easy to check the error type. Return a null value: Use a null value (such as nullptr) to indicate an error, and identify errors by checking the return value. Enumeration type: An enumeration that defines the error type, which is determined by comparing the returned codes.

Alternatives to Exception Handling

In C, when an error or abnormal situation occurs, you can use the exception handling mechanism to deal with them. However, the exception handling mechanism also has some shortcomings, such as it may reduce code performance and increase code complexity. Therefore, in some cases, we can also consider alternatives to using exception handling.

Alternative 1: Error code

Principle:

Use error codes to indicate error conditions. When an error occurs, the function returns a predefined error code, and the caller can determine the error type by checking the error code.

Advantages:

• High performance
• Easy to implement

Example:

#include <iostream>

using namespace std;

int divide(int a, int b) {
  if (b == 0) {
    return -1;  // 返回错误码
  }
  return a / b;
}

int main() {
  int a = 10;
  int b = 0;

  int result = divide(a, b);
  if (result == -1) {
    cout << "除数不能为 0" << endl;
  } else {
    cout << "结果为：" << result << endl;
  }

  return 0;
}

Alternative 2: Return a null value

Principle:

Use a null value (such as nullptr) to indicate error conditions. When an error occurs, the function returns a null value, and the caller can determine the error type by checking whether the return value is nullptr.

Advantages:

• Easy to implement
• Can return structured error information

Example:

#include <iostream>
#include <memory>

using namespace std;

unique_ptr<int> divide(int a, int b) {
  if (b == 0) {
    return nullptr;  // 返回空值
  }
  return make_unique<int>(a / b);
}

int main() {
  int a = 10;
  int b = 0;

  unique_ptr<int> result = divide(a, b);
  if (result == nullptr) {
    cout << "除数不能为 0" << endl;
  } else {
    cout << "结果为：" << *result << endl;
  }

  return 0;
}

Alternative 3: Enumeration type

Principle:

Define an enumeration type to represent different error types. When an error occurs, the function returns an error code belonging to this enumeration type. The caller can determine the error type by comparing the returned error code.

Advantages:

• Good legibility
• Can customize error message

Example:

#include <iostream>

using namespace std;

enum class ErrorType {
  kSuccess,
  kDivideByZero
};

ErrorType divide(int a, int b, int& result) {
  if (b == 0) {
    return ErrorType::kDivideByZero;
  }
  result = a / b;
  return ErrorType::kSuccess;
}

int main() {
  int a = 10;
  int b = 0;
  int result;

  ErrorType error_code = divide(a, b, result);
  if (error_code == ErrorType::kSuccess) {
    cout << "结果为：" << result << endl;
  } else if (error_code == ErrorType::kDivideByZero) {
    cout << "除数不能为 0" << endl;
  }

  return 0;
}

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