C Segmenation fault

OrbiT^ · 04-19-2005, 12:24 PM

Hello,
I'm trying to write a tool that get's information out of the database from 2 tables. Could anybody tell me what's wrong with this code:

Thanks

Code:

#include "/usr/local/mysql/include/mysql/mysql.h"
#include <stdio.h>
#include <string.h>

main() {

   MYSQL *subconn;
   MYSQL *domeinconn;
   MYSQL_RES *sub;
   MYSQL_RES *domein;
   MYSQL_ROW subrow;
   MYSQL_ROW domeinrow;


   char *server = "xxxx";
   char *user = "xxxx";
   char *password = "xxxx";
   char *database = "xxxx";

   subconn = mysql_init(NULL);
   domeinconn = mysql_init(NULL);


   if (!mysql_real_connect(subconn, server,
         user, password, database, 0, NULL, 0)) {
      fprintf(stderr, "%s\n", mysql_error(subconn));
      exit(0);
   }

 if (!mysql_real_connect(domeinconn, server,
        user, password, database, 0, NULL, 0)) {
      fprintf(stderr, "%s\n", mysql_error(domeinconn));
      exit(0);
   }

   /* send SQL query */
   if (mysql_query(subconn, "SELECT * FROM isource_subdomeinen")) {
      fprintf(stderr, "%s\n", mysql_error(subconn));
      exit(0);
   }

   sub = mysql_use_result(subconn);
   domein = mysql_use_result(domeinconn);


   while ((subrow = mysql_fetch_row(sub)) != NULL) {

        if(mysql_query(domeinconn, "SELECT domein_naam FROM isource_domeinnamen WHERE domein_id=3")) {
                fprintf(stderr, "%s\n", mysql_error(domeinconn));
                exit(0);
        }

        while ((domeinrow = mysql_fetch_row(domein) != NULL) {
                printf("%s%s\n", domeinrow[0], subrow[2]);
        }

   }    

   mysql_close(domeinconn);
   mysql_close(subconn);
}

aluser · 04-19-2005, 01:38 PM

Well, there seems to be a missing end brace to the while((subrow = ... loop. Did you miss pasting one before the mysql_close() calls?

aluser · 04-19-2005, 01:39 PM

In any event, when you get a segv the first thing to do is get figure out what line it happens on, either with printfs or (preferably) by gdb on the core file.

OrbiT^ · 04-19-2005, 01:39 PM

Quote:

Originally posted by aluser
Well, there seems to be a missing end brace to the while((subrow = ... loop. Did you miss pasting one before the mysql_close() calls?

yes sorry, forgot to paste that, the brace is not causing the segfault.

gdb doesn't ouput the line, it just tell's me that the error is in the main structure.

aluser · 04-19-2005, 01:42 PM

Quote:

gdb doesn't ouput the line, it just tell's me that the error is in the main structure.

Are you compiling with -g?

OrbiT^ · 04-19-2005, 01:43 PM

No, should i do that?

aluser · 04-19-2005, 01:44 PM

Yes. : ) It includes debugging information in the executable so gdb can get line numbers and variable names.

OrbiT^ · 04-19-2005, 01:48 PM

This is what gdb ouput's:

Code:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1210264160 (LWP 22394)]
0xb7faa592 in mysql_fetch_row () from /usr/lib/libmysqlclient.so.14
(gdb)

OrbiT^ · 04-19-2005, 01:52 PM

aha i've got it to work

Thank you aluser

The line "domein = mysql_use_result(domeinconn);" had to be under the second query.
Stupid me i didn't see that

aluser · 04-19-2005, 02:58 PM

Ah, I spaced for a few minutes there. Next instruction would have been to type "bt" in gdb to get a backtrace : )