GCD recursion function RTE in some IDEs-CodePudding

Trying to implement gcd int function using Euclidean Algorithm with recursion. Results from CodeBlocks differ from IDEone (which I use to test my code before submitting to a CP website, TLX: https://tlx.toki.id, which I assume has similar compilers etc. because a lot of times IDEone and TLX got RTE while in CodeBlocks it ran without any problem). First Question: 1. Do they actually have something different that affects the output?

My first attempt was as follows:

#include <iostream>
#include <cmath>

using namespace std;
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <stdio.h>
#define pass (void)0
#include <cstdio>
#include <cstring>
#define ll long long

int gcd(int x, int y){
    if(y!=0){
        gcd(y, x%y);
        //return x%y;
    } else {
        return x;
    }
}

int main() {
    cout << "test" << endl;
    int z = gcd(100, 10);
    cout << z << " bruh" << endl;
    cout << "hello" << endl;
}

which IDEone spits out

Runtime error #stdin #stdout 0.01s 5380KB
test

while it ran as expected (z = 1 and prints out the correct stuff) in CodeBlocks

I tried to pinpoint where the error exactly occurs by 1. printing out at what part of the code my computer went error by the following way

void gcd(int x, int y){
    if(y!=0){
        cout << "if " << x << ", " << y << endl;
        gcd(y, x%y);
    } else {
        cout << "else " << x << ", " << y << endl;
        //return x;
    }
}

int main() {
    cout << "test" << endl;
    //int z = gcd(100, 10);
    gcd(100, 10);
    //cout << z << " bruh" << endl;
    cout << "hello" << endl;
}

which in both IDE, it outputted:

test
if 100, 10
else 10, 0
hello

then I also tried:

int gcd(int x, int y){
    if(y!=0){
        gcd(y, x%y);
        //return x%y;
    } else {
        return x;
    }
}

int main() {
    cout << "test" << endl;
    int z = gcd(100, 10);
    cout << z << " bruh" << endl;
    cout << "hello" << endl;
}

CodeBlocks outputted the first, while IDEone had an error as in the second

test
10 bruh
hello

Runtime error #stdin #stdout 0.01s 5380KB
test

from what I've tried and understand so far, it seems there's an error when the function gcd() calls the gcd() function. 2. Is my assumption correct? 3. and how am I supposed to solve this problem?

Thanks in advance

CodePudding user response：

The problem is that the recursive case of the gcd() function does not run a return statement. Thus, it should be modified like this:

int gcd(int x, int y){
    if(y!=0){
        return gcd(y, x%y);
    } else {
        return x;
    }
}

This could easily have been caught by enabling and reading compiler warnings.