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What are all the common undefined behaviours that a C++ programmer should know about?
In C++, there are some undefined behaviors. These are identified by doing some tasks in C++. There are no such direct definitions. These few things should be known to all of the programmers, who want to use C++ for different purposes.
Here we will see some C++ Codes. and try to guess the results. The codes will generate some runtime errors.
The Divide By Zero error is undefined.
Example Code
#include <iostream>
using namespace std;
int main() {
int x = 10, y = 0;
int z = x / y;
cout << "Done" << endl;
}Output
Runtime error for divide by zero operation
Trying to use uninitialized variable.
Example Code
#include <iostream>
using namespace std;
int main() {
bool x;
if(x == true)
cout << "true value";
else
cout << "false value";
}Output
false value (This may differ in different compilers)
Trying to access null pointer values.
Example Code
#include <iostream>
using namespace std;
int main() {
int *ptr = NULL;
cout << "The pointer value is: " << *ptr;
}Output
Runtime error for accessing null pointer values
Trying to access null pointer values.
Example Code
#include <iostream>
using namespace std;
int main() {
int array[10];
for(int i = 0; i<=10; i++) {
cout << array[i] << endl;
}
}Output
Runtime error for accessing item out of bound. Some compiler may return some arbitrary value, not return any error Going beyond limit of signed int.
Example Code
#include <iostream>
using namespace std;
int main() {
int x = INT_MAX;
cout << "x + 1: " << x + 1;
}Output
x + 1: -2147483648 circulate to the minimum number of signed int
Trying to change some character in String literals.
Example Code
#include <iostream>
using namespace std;
int main() {
char *str = "Hello World";
str[2] = 'x';
cout << str;
}Output
Runtime error because we are trying to change the value of some constant variables.
Updated on: 30-Jul-2019
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