segmentation fault in passing a char* pointer

Question

I am trying to make a program which checks whether the entered string is palindrome or not using recursion. Here is the following code.

#include <stdio.h>
#include <string.h>

int isPalindrome(char* s, int i, int j) {
    if (i >= j)
        return 1;

    if (s[i] != s[j])
        return 0;

    return isPalindrome(s, i+1, j-1);
}

int main() {

    char* word;
    printf("Enter a word \n");
    scanf("%s", word);

    if (isPalindrome(word, 0, strlen(word) - 1))
        printf("Palindrome \n");
    else
        printf("Not Palindrome \n");

    return 0;
}

The program seems to give a segmentation fault caused by the function isPalindrome(). Where is my code going wrong?

Thank you.

`scanf("%s", word);` invokes *undefined behavior* - you need to initialize the pointer `word` to point at valid (and sufficient) memory first — UnholySheep, Oct 20 '17 at 22:36
You haven't allocated memory for `word`--it's just a pointer. — Lee Daniel Crocker, Oct 20 '17 at 22:39
as said no memory allocated for `word`, you can change it for example like `char word [80];` — macroland, Oct 20 '17 at 22:41
How did you determine the fault was inside `isPalindrome`? The `scanf` should have failed first. — Mark Ransom, Oct 20 '17 at 22:45
Here is the **real duplicate**. https://stackoverflow.com/questions/7709452 I don't know if there's an easy way to correct a vague duplicate to a more accurate one. — Drew Dormann, Oct 20 '17 at 22:48
The descriptions of the error above are more complicated than necessary. It's this simple: You have to assign a variable a value before passing its value to a function. You do not assign `word` a value, but you pass its value to `scanf`. — David Schwartz, Oct 20 '17 at 22:49

score 0 · Accepted Answer · answered Oct 20 '17 at 22:41

0

When you have a character pointer, You should either have another character string which has been allocated and make it point to that

OR you directly dynamically allocate space for a string.

Your code works if you malloc some space

char *word = malloc(20);

or you can just create a string

char word[20];

answered Oct 20 '17 at 22:41

Shaun F

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That worked!! Thanks a lot. – AribAlam Oct 20 '17 at 23:19

segmentation fault in passing a char* pointer

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