why does recursion function works in visual studio eventhough there is no return value

Question

#include <iostream>
using namespace std;

int test(int numb) {
    if (numb == 0) return 0;
    test(numb - 1);
}

int main() {
    cout<<test(10);
}

so i was solving some algorithm questions. this code works in visual studio but not in other online shell. what does test() function returning even though there is no return? also

#include <iostream>
#include<stdio.h>
using namespace std;

int test(int numb) {
    if (numb == 0) return 0;
    cout<<test(numb - 1)<<endl;
}

int main() {
    cout<<test(10);
}

//result
0
1349009568
1349009568
1349009568
1349009568
1349009568
1349009568
1349009568
1349009568
1349009568
1349009568

what does thoes number 1349009568 means??

You have *undefined behavior!* If you declare that a function should return a value, you should actually return a value. — Some programmer dude, May 07 '20 at 06:48
`main` is an allowed exception in C++. The standard says you are allowed to not return from `main`, and it will assume `return 0` — Tas, May 07 '20 at 06:51
Also, this answer https://stackoverflow.com/a/32513935/1611055 has a more detailed (X86 specific) example why in certain conditions your code still might seem to work — Andreas Fester, May 07 '20 at 06:52
You should also take a look at your compiler settings. The compiler can warn you about this. — Lukas-T, May 07 '20 at 07:05

score 0 · Accepted Answer · answered May 07 '20 at 06:52

Your function has undefined behavior when it doesn't return anything. The number 1349009568 is meaningless and probably random. For me, it shows a 0, and has the same output as this version which will never return anything.

int test(int numb) {
    if (false) return -1;
}

why does recursion function works in visual studio eventhough there is no return value

1 Answers1