Re: [Vala] SQLite segfault when used in a class

["Travis Watkins" <amaranth ubuntu com>]

On Jan 11, 2008 11:38 AM, Alessandro Pellizzari <alex amiran it> wrote:
> Hi all,
>
> I am trying to use SQLite. I followed the site tutorial.
>
> BTW, there is an error in the example:
>
> rc = Database.open(args[1], ref db);
>    if ( rc == 0 ) { // SQLITE_OK -> Sqlite.OK == 0
>
> it should be:
>
>    if ( rc != 0 ) { // SQLITE_OK -> Sqlite.OK == 0
>
>
> That corrected, I compiled the demo flawlessly, but when I try to create
> a class to manage my DB I get a segfault on the callback:
>
> public class Storage : GLib.Object
> {
>   private Sqlite.Database db;
>
>   public void test()
>   {
>     string errmsg;
>     int rc;
>
>     rc = Sqlite.Database.open("test.sq3", ref this.db);
>     if (rc != 0) {
>       GLib.stdout.printf("DB error: %s\n", this.db.errmsg);
>     }
>
>     rc = this.db.exec("select * from myt;", callback, null, ref errmsg);
>
>     if (rc != 0) {
>       stderr.printf("SQL error: %s\n", errmsg);
>     }
>   }
>
>   public static int callback(pointer data, int n_columns, string[]
> values, string[] column_names)
>   {
>     for (int i = 0; i < n_columns; i++) {
>         // HERE it segfaults:
>       GLib.stdout.printf("%s = %s\n", column_names[i], values[i]);
>     }
>     GLib.stdout.printf("\n");
>
>     return 0;
>   }
> }
>
> public class Main : GLib.Object
> {
>   static int main (string[] args) {
>
>     var db = new Storage();
>     db.test();
>   }
> }
>
> It seems that the parameters get "shifted left by one". I tried printing
> the values, and I found that values[0] contains the column name of the
> first column, while column_name[0] points to nowhere, giving the
> segfault.
>
> Am I doing something wrong?
>
> Thank you very much.
>
>
> --
> Alessandro Pellizzari


Your callback method should be decorated with [InstanceLast] and you
should pass 'this' in as the user data in the exec call (I think
that's what the null area is for anyway).


-- 
Travis Watkins
http://www.realistanew.com