If I modify the string key example to check for duplicates before adding new entries, it dies

[Sir Barksalot]

The example works fine, until I add code to check for duplicates. The output is then "Segmentation fault (core dumped)"
I'm figuring it must be a rookie mistake. Can anybody spot where I've gone wrong? I've commented my changes below

#include <string.h>  /* strcpy */

#include <stdlib.h>  /* malloc */

#include <stdio.h>   /* printf */

#include <uthash.h>

struct my_struct {

    char name[10];             /* key (string is WITHIN the structure) */

    int id;

    UT_hash_handle hh;         /* makes this structure hashable */

};

int main(int argc, char *argv[]) {

    // modified this line to add duplicates

    const char *names[] = { "joe", "bob", "betty", "johnny", "betty", "johnny", "bob", "joe", NULL };

    struct my_struct *s, *tmp, *users = NULL;

    for (int i = 0; names[i]; ++i) {

        s = (struct my_struct *)malloc(sizeof *s);

        strcpy(s->name, names[i]);

        s->id = i;

        // added the lines below to check for duplicates

        HASH_FIND_STR( users, names[i], s);

          if (s) {

            printf("Danger, duplicate detected: %s\n", names[i]);

          } else {

            HASH_ADD_STR( users, name, s );

          }

    }

    HASH_FIND_STR( users, "bob", s);

    if (s) printf("%s's id is %d\n", s->name, s->id);

    for(s=users; s != NULL; s=s->hh.next) {

        printf("user id %d: name %s\n", s->id, s->name);

    }

    /* free the hash table contents */

    HASH_ITER(hh, users, s, tmp) {

      HASH_DEL(users, s);

      free(s);

    }

    return 0;

}

[cro...@gmail.com]

HASH_FIND_STR was clobbering s. Try:

   for (int i = 0; names[i]; ++i) {

      s = (struct my_struct *) malloc(sizeof *s);

      strcpy(s->name, names[i]);

      s->id = i;

      HASH_FIND_STR(users, s->name, tmp);

      if (tmp)

         printf("Danger, duplicate detected: %s\n", s->name);

      else

         HASH_ADD_STR(users, name, s);

[Sir Barksalot]

Brilliant. Thanks for the insight.

SB

[cro...@gmail.com]

Also you’d want to check for the key’s presence before, rather than after, allocating a new node.