resetting sqlite statements and cancellation

[Stefan Sperling]

We have this pattern in several places within wc_db:

  svn_sqlite__get_statement(&stmt, ...)
  svn_sqlite_step(&have_row, stmt);
  while (have_row)
    {
      if (cancel_func)
        SVN_ERR(cancel_func(cancel_baton));

      /* do stuff */  

      svn_sqlite_step(&have_row, stmt);
    }
  svn_sqlite_reset(stmt);

So a cancellation handler can return without resetting the SQL statement.

This is probably not an issue with the CLI client which will just exit.
But what about GUI clients? If the user clicks a cancel button and tries
another operation that reuses the statement, will there be a problem?

If so, what's the best way to solve this?
I think it would be ugly to check the return value of cancel_func manually.
What about a convenience SVN_ERR-like macro that also accepts a statement
and resets it in case an error is thrown?

      if (cancel_func)
        SVN_ERR_RESET_STMT(cancel_func(cancel_baton), stmt);