json-c: segmentation fault when in json_tokener_parse

Question

I am using json-c to parse json files in my project. I tried creating json_tokener_parse but this has resulted in seg-fault. could any please check and tell me the reason for segfault.

#include <sys/mman.h> 
#include <sys/stat.h>
#include <fcntl.h> // O_RDONLY
#include<stdlib.h>
#include<stdio.h>
#include<unistd.h>
#include<json-c/json.h>

int main() {
    int oflag = O_RDONLY;
    const char *path = "file.json";
    const int fd = open(path, oflag);

    // use stat to find the file size
    struct stat stat;
    int ret = fstat(fd, &stat);

    int mflags = MAP_SHARED; // information about handling the mapped data
    int mprot = PROT_READ|PROT_WRITE; // access permissions to the data being mapped 
    size_t size = stat.st_size;
    void *addr = mmap(NULL, size, mprot, mflags, fd, 0);
    const char *file = (char *)addr;

    json_object * jobj = json_tokener_parse(addr);     
    //json_parse(jobj);
}

Have you written in a check that mmap returns a non-NULL pointer? — Thomas Jager
– Thomas Jager, Commented May 24, 2018 at 17:39
I tried adding that check, even after that, I still get seg fault. — BODDU MANOHAR REDDY
– BODDU MANOHAR REDDY, Commented May 25, 2018 at 7:08

BODDU MANOHAR REDDY · Accepted Answer · 2018-05-25 15:46:06Z

1

json_tokener_parse() takes a null-terminated string. A text file is not null-terminated. You'll have to use json_tokener_parse_ex() and specify the length.

answered May 25, 2018 at 15:46

BODDU MANOHAR REDDY

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