This code gets stuck and I don't know why

Question

#include<stdio.h>

int sum_digit(int);

int main()
{
    int a;
    printf("Enter no. for which we want the sum of digits\n");
    scanf(" %d", &a);
    printf("Some of digit %d", sum_digit(a));
    return 0;
}

int sum_digit(int num)
{
    int sum = 0;
    while(num > 0);
    {
        sum = sum + num % 10;
        num = num / 10;
    }
}

When I run this code it asks for value but as I hit enter it gets stuck. Not able to understand why it is not producing any results.

Is this the problem of whites spaces with scanf?

First of all indent your code properly. – Jabberwocky May 20 '20 at 12:14 — Jabberwocky, May 20 '20 at 12:14
`sum_digit` needs to return something. – kaylum May 20 '20 at 12:15 — kaylum, May 20 '20 at 12:15
`while(num>0);` <== infinite loop with empty body – pmg May 20 '20 at 12:15 — pmg, May 20 '20 at 12:15

score 3 · Answer 1 · edited May 20 '20 at 12:59

3

While loops (as well as for loops and if statements), in the typical use cases, don't have a semicolon at the end. That being said, you have an extra semicolon at the end of the line: while(num > 0);. Remove the semicolon for the expected behavior.

As pointed out in comments, the function int sum_digit(int) will result in an undefined behavior because it doesn't return anything. Add return sum; at the end of the function to fix that.

Here's the final code:

#include<stdio.h>

int sum_digit(int);

int main()
{
    int a;
    printf("Enter no. for which we want the sum of digits\n");
    scanf(" %d", &a);
    printf("Some of digit %d", sum_digit(a));
    return 0;
}

int sum_digit(int num)
{
    int sum = 0;
    while(num > 0)
    {
        sum = sum + num % 10;
        num = num / 10;
    }
    return sum;
}

Using a semicolon at the end can be useful sometimes.

edited May 20 '20 at 12:59

RobertS supports Monica Cellio

14,524
7
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80

answered May 20 '20 at 12:21

PajLe

791
1
7
21

Sure, I can agree with that. I guess it depends on the compiler. I used the vs2017 c++ one. – PajLe May 20 '20 at 12:48
1

Nice cat btw. I got 3. – RobertS supports Monica Cellio May 20 '20 at 13:00
Love that! :D I don't have any though, just found this somewhere online – PajLe May 20 '20 at 13:01
And Visual Studio 2017 shows warnings and/or errors for no return value? – RobertS supports Monica Cellio May 20 '20 at 13:21
In vs2017 I get an error `error C4716: 'sum_digit': must return a value` – PajLe May 20 '20 at 15:00
1

Update: Didn´t tried it with `-Wall` before. I was in a hurry. Me fool. - Then it actually shows warnings for both. – RobertS supports Monica Cellio May 20 '20 at 17:06

RobertS supports Monica Cellio · Accepted Answer · 2020-05-21T08:42:07.400

Your code has two issues:

while(num > 0); - There is a semicolon ; after the loop condition, which results in that the loop´s body won´t be treated as loop body - the while loop will just constantly proof the condition and as num does not change, the loop goes infinitely.
The function sum_digit() does not return anything.

Thus, To use printf("Some of digit %d", sum_digit(a)); invokes undefined behavior.

return sum; at the end of sum_digit().

Note: If you use GCC, the -Wall option had showed you warnings for both.

score 1 · Answer 3 · answered May 20 '20 at 12:17

1

Your while loop is infinite. You need to remove the semi-colon. A while loop looks like this

while(condition) {
    statement(s);
}

Your while loop does nothing, but keeps running if num>0

answered May 20 '20 at 12:17

RetardedHorse

148
1
7

This code gets stuck and I don't know why

3 Answers3