Getting Segmentation fault when trying to read a json file - c

Question

I'm trying to parse a json file using jsmn but I get segmentation fault when I run my application. I'm using C and compiling on Ubuntu machine.
Please find the code snippet below:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "jsmn.h"
#define JSON_FILE_PATH "/home/admin/Desktop/test/server/dataFile.json"
#define BUFFER_SIZE 5000
#define MAX_TOKEN_COUNT 128
// Read files
void readfile(char* filepath, char* fileContent)
{
FILE *f;
char c;
int index;
f = fopen(filepath, "r");
***while((c = fgetc(f)) != EOF){*** ------> seg fault
fileContent[index] = c;
index++;
}
fileContent[index] = '\0';
}
// This is where the magic happens
int parseJSON(char *filepath, void callback(char *, char*)){
char JSON_STRING[BUFFER_SIZE];
char value[1024];
char key[1024];
readfile(filepath, JSON_STRING);
int i;
int r;
jsmn_parser p;
jsmntok_t t[MAX_TOKEN_COUNT];
jsmn_init(&p);
r = jsmn_parse(&p, JSON_STRING, strlen(JSON_STRING), t, sizeof(t)/(sizeof(t[0])));
if (r < 0) {
printf("Failed to parse JSON: %d\n", r);
return 1;
}
/* Assume the top-level element is an object */
if (r < 1 || t[0].type != JSMN_OBJECT) {
printf("Object expected\n");
return 1;
}
for (i = 1; i < r; i++){
jsmntok_t json_value = t[i+1];
jsmntok_t json_key = t[i];
int string_length = json_value.end - json_value.start;
int key_length = json_key.end - json_key.start;
int idx;
for (idx = 0; idx < string_length; idx++){
value[idx] = JSON_STRING[json_value.start + idx ];
}
for (idx = 0; idx < key_length; idx++){
key[idx] = JSON_STRING[json_key.start + idx];
}
value[string_length] = '\0';
key[key_length] = '\0';
callback(key, value);
i++;
}
return 0;
}
// Only prints the key and value
void mycallback(char *key, char* value){
printf("%s : %s\n", key, value);
}
int main()
{
parseJSON(JSON_FILE_PATH, mycallback);
return 0;
}
I get segmentation fault after the line as indicated when the file operation of reading is done.
On debugging, at this point f contains 0x00 value which means it is not able to identify the file.
Why this might be happening when file is present at that location?
I tried changing paths but still same issue.

Answer 1

Found the solution:
index is not initialized before use
char c should be int c - fgetc returns an int