自定义异常what()返回“std::Exception”

Question

在这里，我刚刚构建了一个自定义异常，但在抛出并捕获它之后，异常的 What 方法没有返回应有的原因。相反，它只是返回“std::exception”。

#include <stdexcept>
#include <iostream>
#include <cstring>

class CustomException: public std::exception {
  public: std::string m_reason;
  CustomException(std::string reason): m_reason(reason) {}
  const char * what() {
    return m_reason.c_str();
  }
};

void
function () {
  throw CustomException("no reason");
}

int main() {
  try {
    function ();
  } catch (const std::exception & e) {
    std::cout << e.what() << std::endl;
  }
}

Answer 1

我花了很长时间才弄清楚什么方法缺少

const noexcept override

注释来正确重写具有签名

what

的 std::exception 类的

virtual const char* what() const noexcept;

方法（自 C++11 起）

#include <stdexcept>
#include <iostream>
#include <cstring>

class CustomException: public std::exception {
  public: std::string m_reason;
  CustomException(std::string reason): m_reason(reason) {}
  const char * what() const noexcept override{
    return m_reason.c_str();
  }
};

void
function () {
  throw CustomException("no reason");
}

int main() {
  try {
    function ();
  } catch (const std::exception & e) {
    std::cout << e.what() << std::endl;
  }
}