Confused about the function return value

Question

#include
using namespace std;
int Fun(int x)
{
    int sum=1;
    if(x>1)
        sum=x*Fun(x-1);
    else
        return sum;
}
int main()
{
             


        

Answer 1

When your program pass in the if condition, no return statement finish the function. The number you got is the result of an undefined behavior.

int Fun(int x)
{
    int sum=1.0;
    if(x>1)
        sum=x*Fun(x-1);
    else
        return sum;

    return x; // return something here
}