In C++, the compiler adds a
return 0;
statement to the main() function of a program if the function returns an int result and does not end with a user return statement.
Examples:
int main() { } // equivalent to:
// int main() { return 0; }
main() { } // equivalent to:
// int main() { return 0; }
If you enable the ANSI Strict setting , the compiler enforces an external int main() function.