throw does not show error msg c++

Question

Final update: Thank you for all the comments and help. I went back to the textbook and copied the whole code to run their program, and realized their throw message never appeared, I assumed there message would appear which is why I was expecting a message to appear on my program which is why I didn't use a try/catch. Thank you again for the help guys/gals.

I'm working on an assignment and for some reason the throw invalid_argument will not display the message "Account balance is too low".

I pretty much took the code from my text book

void setBaseSalary(double salary) {
  if (salary<0.0){
    throw invalid_argument("Salary must be >= 0.0");
   }
}

and created my own....

void Account::setAccountBalance(double accountBalanceVar)
{
    cout << accountBalanceVar << "B4 IF" << endl;
    if (accountBalanceVar < 0.0) {
        cout << accountBalanceVar << "B4 while in IF" << endl; 
        throw invalid_argument("Account balance is too low"); // program err      
        accountBalanceVar = 0.0;
        cout << accountBalanceVar << "In IF" << endl;
    }
    accountBalance = accountBalanceVar;
}

The cout was me debugging where the program stop working, which lead me to the throw.

Here is my full code to replicate the error, i'm using -5 for my input

#include <iostream>
#include <iomanip>
#include "savingAccount.h"
#include "checkingAccount.h"
#include "Account.h"

// header

using namespace std;

int main() {

    double userAccountBalance{ 0.0 };

    cout << "Enter your account Balance: " << endl;
    cin >> userAccountBalance;

    Account myAccount{ userAccountBalance };

    return 0;
}

#include "Account.h"
#include <iostream>
#include <iomanip>
#include <string>
#include <stdexcept>
#include <sstream>

using namespace std;



Account::Account(double accountBalanceVar) {

    setAccountBalance(accountBalanceVar);
    cout << accountBalance << ": Tester: constructor" << endl;
}

double Account::credit(double addBalance)
{
    accountBalance+=addBalance;

    return accountBalance;
}

double Account::debit(double withDrawnVar)
{
    if (accountBalance < withDrawnVar) {

        cout << "Error : You can not withdrawn more than your total balance";
        withDrawnVar = 0; // To ensure unchange

}
    accountBalance -= withDrawnVar;

    return withDrawnVar;
}

Account::~Account()
{
}

void Account::setAccountBalance(double accountBalanceVar)
{
    cout << accountBalanceVar << "B4 IF" << endl;
    if (accountBalanceVar < 0.0) {
        cout << accountBalanceVar << "B4 while in IF" << endl;
        throw invalid_argument("Account balance must be >= 0.0");
        accountBalanceVar = 0.0;
        cout << accountBalanceVar << "In IF" << endl;
    }
    accountBalance = accountBalanceVar;

}

double Account::getAccountBalance()
{
    return accountBalance;
}


#include <iostream>
#include <iomanip>
#include <string>

#ifndef ACCOUNT_H
#define ACCOUNT_H 
class Account
{
public:
    Account(double = 0.0);
    double credit(double);
    double debit(double);


    ~Account();


    void setAccountBalance(double);
    double getAccountBalance();

private:
    double accountBalance{ 0.0 };
    double zeroBalance{ 0.0 };

};

#endif

Update:

What symptoms are you seeing? What inputs are you using? The program stop after the input (Using -5 as input) " cout << accountBalanceVar << "B4 while in IF" << endl; "

The command will display -5, the throw will not display and the program stops.

I did not use a try/catch because the example of the textbook didn't use it, I'm confused why the textbook version works and my doesn't..it's almost identical.

You'll have to give more details. What do you mean "the throw invalid_argument does not want to work"? What symptoms are you seeing? What inputs are you using? What does the code that calls the function look like? — Michael Albers, Mar 25 '17 at 20:46
Where are handling the exception? Where is your `try...catch` statement? — Ervin Szilagyi, Mar 25 '17 at 20:50
Are you expecting to see the text printed by the `cout` after the `throw`? The program will never get there. May we have a [mcve] so that we have enough information to provide good advice? — user4581301, Mar 25 '17 at 20:56
Who says that exception parameters are always printed? Do you have no catch? — deviantfan, Mar 25 '17 at 20:57
Waffling over the correct close vote for this question: Unclear what you are asking or off topic (lacking code to reproduce error) — user4581301, Mar 25 '17 at 21:04
@jaye31987 Probably, textbook version works, and yours doesn't, because of that _**almost**_ in _almost identical_. — Algirdas Preidžius, Mar 25 '17 at 21:11
@jaye31987 You should read about exception handling a bit more: http://www.cplusplus.com/doc/tutorial/exceptions/ If your textbook does not speak about `try...catch` than probably you should throw it away. — Ervin Szilagyi, Mar 25 '17 at 21:15
[Your code works](http://coliru.stacked-crooked.com/a/c84457b863f95927), it probably just doesn't do what you _want_ it to do. The two lines after the `throw` will never be reached, because throwing moves execution to the nearest containing `try` block that can `catch` what you threw. In this case, since the closest containing `try` is in `main()`, throwing causes it to do any required cleanup in `setAccountBalance()`, then back up until it gets back to the `try` block, so it can check if there's a `catch` for `std::invalid_argument`; since it's derived from `std::exception`, the `catch` — Justin Time - Reinstate Monica, Mar 25 '17 at 21:20
block there works. If there wasn't an appropriate `catch` block there, it would back up some more and try to find the next closest `try` block, and so on until it finds one that can `catch` a `std::invalid_argument`, or terminate execution if it couldn't find one. — Justin Time - Reinstate Monica, Mar 25 '17 at 21:22
[Here's](http://coliru.stacked-crooked.com/a/4c714eac983c67ca) a little illustration of how `throw` moves execution to the appropriate `catch` block. — Justin Time - Reinstate Monica, Mar 25 '17 at 21:55
@jaye31987 Also, you don't actually need `type_traits` for anything in there, that's just something I used while testing something, but forgot to remove after. — Justin Time - Reinstate Monica, Mar 26 '17 at 01:52

score 1 · Accepted Answer · answered Mar 25 '17 at 21:14

Exceptions are handled by try/catch statements. You would need to add one in order to catch your exception and print its value.

try {
  Account myAccount{ -5.0 }; // Assuming this calls setAccountBalance
} catch (const std::invalid_argument &e) {
  std::cerr << "Exception: " << e.what() << std::endl;
}

If you never catch the exception, the terminate function is called. It will stop your executable. C++ isn't like Java in that unhandled exceptions are not printed. If you're running on Linux and have core file generation enabled then a core file will be generated.

throw does not show error msg c++

1 Answers1