c - Initializing a nested structure -

this problem learn c hardway. database management system in c have 3 structures :-

 struct address {          int id;          int set;          char *name;          char *email;  };   struct database { int rows;     struct address *row;  };   struct connection {     file *file;     struct database *db;  }; 

i trying initialize database structure. getting segfault

    void database_create(struct connection *conn, int no_of_rows)     {       int = 0;   conn->db->row_num = no_of_rows;         for(i = 0; < conn->db->row_num; i++) {        // make prototype initialize       struct address addr;       addr.id = i;       addr.set = 0;        // assign       conn->db->rows[i] = addr;       }   } 

i've made function allocates memory these structures.

     struct connection *database_open(const char *filename, char mode)       {            struct connection *conn = malloc(sizeof(struct connection));         if(!conn) die("memory error");      int number = conn->db->rows;          conn->db = malloc(sizeof(struct database));     if(!conn->db) die("memory error");          conn->db->row = malloc(sizeof(*conn->db->row) * number);         if(!conn->db->row) die("memory error");          if(mode == 'c') {         conn->file = fopen(filename, "w");         } else {          conn->file = fopen(filename, "r+");        if(conn->file) {          database_load(conn);       }    }     if(!conn->file) die("failed open file");        return conn;    } 

valgrind says "use of uninitialized value of size 4" in database_open()

could suggest might doing wrong here?

db in connection , row in database uninitialised pointers. need initialise them , provide storage structs point to.

you can save dynamic allocation changing connection have database member rather pointer

struct connection {     file *file;     struct database db;  }; 

you need allocate memory database rows

conn->db.row = malloc(no_of_rows * sizeof(*conn->db.row)); 

database_create like

int database_create(struct connection *conn, int no_of_rows) {     int = 0;     conn->db.rows = no_of_rows;     conn->db.row = malloc(no_of_rows * sizeof(*conn->db.row));     if (conn->db.row == null) {         /* out of memory */         return 1;  /* indicate failure caller */     }     for(i = 0; < conn->db->rows; i++) {         conn->db.row[i].id = i;         conn->db.row[i].set = 0;     }     return 0; /* indicate success caller */ } 

note assumes memory allocated connection