C ++自定义异常消息未显示 [英] C++ custom exception message not displaying

问题描述

我试图创建一个自定义的异常类，将其抛出并显示错误消息，但是我做错了事，导致未引发该异常并且该消息未得到打印.

I am trying to create a custom exception class, throw it, and display the error message, but I am doing something wrong, causing the exception to not get thrown and the message to not get printed.

这是异常类:

class UnbalancedParenthesesException : public std::exception {
  int line_number {0};
public:
  UnbalancedParenthesesException(int line_number) :
    line_number { line_number }
    {}

  virtual const char* what() const throw() {
    std::string exception_message =
      "Papentheses imbalance at line " + std::to_string(line_number) + "\n";

    return exception_message.c_str();
  }
};

我正尝试 try / throw / catch ，如下所示:

I am trying totry/throw/catch as follows:

void handle_closed_paren(int line_number) {
  try { 
    if (definitely_unbalanced()) {
      throw UnbalancedParenthesesException(line_number);
    }
  } catch (const UnbalancedParenthesesException& e) {
      std::out << e.what() << "\n";
}

控制台中与此错误无关.

There is nothing pertinent to this error in the console.

谢谢.

推荐答案

当您在 std :: string 上返回 c_str()的结果时，您的程序具有未定义的行为代码>超出范围.任何事情都可能发生.

Your program has undefined behaviour as you are returning the result of c_str() on a std::string that goes out of scope. Anything could happen.

除此之外，如果您没有看到异常，则不会引发异常，可能是因为 definitely_unbalanced()的结果是错误的.

Beyond that, if you're not seeing an exception then one was not thrown, probably because the result of definitely_unbalanced() is falsey.

使用调试器逐步执行程序.

Step through your program using your debugger.

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