[Freeciv-Dev] Re: (PR#3546) "Arhus is bugged:" - crash

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

Raimar Falke wrote:
> On Fri, Feb 28, 2003 at 03:41:55AM -0800, ChrisK@xxxxxxxx wrote:

> I'm not able to solve it. The problem is that auto_arrange_workers
> spends more workers that the city has. With the attached patch you get
> an output like:
> 
> 2: auto_arrange_workers finished
> 2: auto_arrange_workers for Århus, size=5
> 2: all workers removed
> 2: Århus: placing worker at (1, 1)
> 2: Århus: placing worker at (3, 0)
> 2: Århus: placing worker at (1, 3)
> 2: Århus: placing worker at (1, 0)
> 2: Århus: placing worker at (2, 3)
> 2: Århus: placing worker at (2, 4)
> 2: Århus: placing worker at (2, 0)
> 2: Århus: placing worker at (2, 1)
> 2: auto_arrange_workers finished
> 1: Århus is bugged: size:5 workers:7 elvis: 0 tax:0 sci:0
> 
> Reason unknown.

The actual error happens because worker_loop calls 
server_set_worker_city, which calls server_set_tile_city, which calls 
update_city_tile_status, which calls add_adjust_workers, which calls 
worker_loop.  Thus we place citizens 5, 4 and 3, then re-enter the loop 
to place 2 and 1, then end that loop and return to the original loop 
where we place 2 and 1 again.

problem is two-fold:

- worker_loop calls server_set_worker_city to make its change. 
server_set_worker_city is _way_ too high-level a function to be called 
by worker loop; it does all sorts of error handling on its own 
(including the call to add_adjust_workers).

- worker_loop is trying to place a unit on a (seemingly) invalid tile. 
worker_loop calls can_place_worker_here, which return TRUE...but 
update_city_tile_status calls city_can_work_tile to perform the 
(seemingly) identical check, and this return FALSE.  Looking at those 
two functions, it seems likely that the error is that the citymap is not 
updated correctly somewhere else.  But I see no way to track this down 
aside from adding sanity checks all over the place.

The attached patch should help to clear up the problem.  I'd suggest 
that for 1.14 worker_loop should call city_can_work_tile to *verify* 
that it is valid before trying to use it.  For cvs HEAD we should fix 
both of the above problems.

jason