How to register exceptions in C ++?

Question

When writing a function, my implementation very often looks like this:

• Subfunction call
• If this sub-function fails (due to an exception): register this failure and interrupt the current function
• Otherwise, continue to call other subfunctions, which, in turn, may fail

The most important part is registration. Each failed function should add a short description to the log. Thus, at the level where the exception is handled, a detailed error message may be displayed to the user.

For example, consider an application in which a new user account can be created and there is a problem connecting to the database. The following reverse stack trace:

• SQLDriverConnect () → "SQLDriverConnect Error: Data Source Not Found and Default Driver Not Specified"
• OpenDatabaseConnection () → "Failed to open database connection"
• CreateUser () → "Failed to create a new user"
• ValidateAndSaveNewUserAccount () → "Failed to save user profile"
• Catch exception and show logged messages to user

Using the exception function, I would do it as follows:

void CreateUser()
{
    try {
        OpenDatabaseConnection();
    }
    catch(std::exception& e) {
        e.AddLog("Failed to create the new user");
        throw;
    }
    //...
}

Using a simple return value, I would write the following:

bool CreateUser(Log& log)
{
    if (!OpenDatabaseConnection(log))
    {
        log.Add("Failed to create the new user");
        return false;
    }
    //...
    return true;
}

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Answer 1

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void OpenDatabaseConnection()
{
   if (Error) throw MyException("Failed opening database");
}

void CreateUser()
{
    try {
        OpenDatabaseConnection();
        //...... do everything here
    }
    catch(MyException& E) { //only one copy of this code
        E.AddLog(E.getMessage());
        throw;
    }
}

Answer 2

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bool CreateUser(Log& log, UserSecurityContext& u) {
    if (!HasPermissionsFor(u, SecurityRoles::AddUser)) {
        log.Add("Insufficient permissions");
        return false;
    }
    //...
    return true;
}

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Answer 3

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Answer 4

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---

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procedure exceptionTest(...)
{
  try
  {
    call1();
    call2();
    call3();
    call4();
  } 
  catch (...)
  {
    //errorhandling outside the normal control flow
  }
}

:

procedure normalTest(...)
{
   if (!call1())
   {
     //errorHandling1
   } 
   else if (!call2())
   {
     //errorHandling2
   }
   else if ....
   ...
}

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Answer 5

. . log not great errors .

:

int someMethod{
    if(erorr_file_not_found){
        logger.add("File not found");
        return 1;
    }

    if(error_permission){
        logger.add("You have not permissons to write this file");
        return 2;
    }

    return 0;
}

.

( ):

int someMethod{
    int retval=0;
    if(someshit){
        retval=1;
        goto _return;
    }
    //...
    _return:
    switch(retval){
        case 1:logger.add("Situation 1");break;
        case 2:logger.add("Situation 2");break;
        //...
    }
    /*
    close files, sockets, etc.
    */
    return retval;
}

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Answer 6

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void CreateUser()
{
      OpenDatabaseConnection();
}

, OpenDatabaseConnection().

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Answer 7

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  void CreateUser() {
      try {
         CDatabaseConnection db = ConnectToDatabase(); 
         InsertIntoDB(db, "INSERT INTO ... "); 
         SetPermission(...);
      } catch(...) {}
  }
  

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