Re: [libmicrohttpd] Segfault

[Christian Grothoff]

Remove MHD_OPTION_NOTIFY_COMPLETED --- or pass two extra arguments with 
the function and closure you want MHD to call upon completion. Right 
now, you're telling MHD to jump to a bad address upon connection completion.

On 3/3/23 15:02, klemens wrote:
> Hi all,
>
> I have an issue with a segfault I can't localize. I run MHD
> from a binary package for DEBIAN11 and start the server with
> the following code (similar to the post example) to serve a
> GET request:
>
> int
> main (int argc, char **argv)
> {
>         time_t now;
>         struct timeval tv;
>         struct timeval *tvp;
>         fd_set rs;
>         fd_set ws;
>         fd_set es;
>         MHD_socket max;
>         MHD_UNSIGNED_LONG_LONG mhd_timeout;
>
>         mylast_alive = (unsigned int)time(&now);
>      if (!(hka = hkaconn ()))
>      {
>          fprintf (stderr, "%s\n", mysql_error(&hkahdl));
>          exit (1);
>      }
>         srand ((unsigned int)time(&now));
>         vbad =
>         MHD_start_daemon (      MHD_USE_ERROR_LOG,
>                                                 1431,
>                                                 &on_client_connect, myclient_ip,
>                                                 &create_response, NULL,
>                          MHD_OPTION_NOTIFY_COMPLETED,
>                          MHD_OPTION_CONNECTION_TIMEOUT, (unsigned int)120,
>                          MHD_OPTION_CONNECTION_LIMIT, (unsigned int)500,
>                                                 MHD_OPTION_END
>                                          );
>         if (NULL == vbad)
>                 return (emsg ("Can't create daemon"));
>         while (1)
>         {
>                 expire_sessions ();
>                 printf ("Nach EXP_SESS\n");
>                 max = 0;
>                 FD_ZERO (&rs);
>                 FD_ZERO (&ws);
>                 FD_ZERO (&es);
>                 if (MHD_YES != MHD_get_fdset (vbad, &rs, &ws, &es, &max))
>                         break; /* fatal internal error */
>                 if (MHD_get_timeout (vbad, &mhd_timeout) == MHD_YES)
>                 {
>                 tv.tv_sec = mhd_timeout / 1000;
>                 tv.tv_usec = (mhd_timeout - (tv.tv_sec * 1000)) * 1000;
>                 tvp = &tv;
>                 }
>                 else
>                 tvp = NULL;
>                 if (-1 == select (max + 1, &rs, &ws, &es, tvp))
>                 {
>                 if (EINTR != errno)
>                 abort ();
>                 }
>                 printf ("Nach SELECT\n");
>                 MHD_run (vbad);
>                 printf ("Nach RUN\n");
>                 
>         }
>         MHD_stop_daemon (vbad);
>         return 0;
> }/*end main*/
>
> The request is properly served and the webpage appears on the
> browser as it should. create_response() ends like this:
>
>         {
>          ....
>             ret = MHD_queue_response (connection, MHD_HTTP_OK, response);
>             MHD_destroy_response (response);
>                 printf ("Nach destroy\n");
>             return MHD_YES;
>         }
>
> Immediately after the printout, I get a segfault. Using gdb yields
>
> Reading symbols from ./vbad...
> (gdb) run
> Starting program: /home/klemens/progc/vba/vbad
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library
> "/lib/x86_64-linux-gnu/libthread_db.so.1".
> Nach EXP_SESS
> Nach SELECT
> Nach RUN
> Nach EXP_SESS
> Nach SELECT
> CR1
> CR2
> CR3
> URL>>/nz7eR48JKpV/GU0t36aWnw==<<
> NEWSN>>5CA207CF66C5FC7378B31FD151F8ECC9|1<<
> Nach GETPAGE
> Nach destroy
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000000000000003 in ?? ()
>
> and I have no idea what causes the segfault and where this
> happens. Any help is higly appreciated.
>
> kginbg.