<URL: http://bugs.freeciv.org/Ticket/Display.html?id=39330 >

> <URL: http://bugs.freeciv.org/Ticket/Display.html?id=39330 >
> Jason Short wrote:
> > <URL: http://bugs.freeciv.org/Ticket/Display.html?id=39335 >
> >>    Attached to this message is a patch to fix the issue reported in
> >> PR#39330. Basically, the problem seems to be that cities can see unknown
> >> terrain, and this is considered acceptable and normal. But, in at least
> >> one place in the code that possibility is overlooked. In a player's view
> >> of a tile, the terrain ptr may be NULL (indicating it is unknown).
> >> Attempts to reference a member, such as 'type', of such a NULL ptr
> >> obviously results in a segfault.
> >
> > Good catch but the bug is deeper.  We do NEED to know the terrain type
> > here since the tile is being sent as TILE_KNOWN_FOGGED.  Can you find
> > a way to reproduce the problem and figure out why a "known" tile has
> > unknown terrain type?  That should not be possible.
> Well, the patch can be easily be modified to send 'TILE_UNKNOWN'
> instead, for the case when the tile is seen by a city, but unknown.
> A *seen* tile is allowed to be *unknown* according to a comment in
> server/maphand.c, starting at line 810 on the SVN head revision, which I
> quote here:

A tile can be known but not seen.  In this case the tile should be
marked as TILE_UNKNOWN in the player tile, NOT as TILE_KNOWN_FOGGED.
This isn't an error in the network code - it's an error in whatever
code marked the plrtile as TILE_KNOWN_FOGGED yet didn't set the

The vision code *has* changed recently so there is a reasonable chance
of errors of this type.  If we're able to reproduce it I can probably
track it down next week, but if you can find the error yourself that
would naturally be even better.

> /****************************************************************************
>    Return whether the player can see the tile.  Seeing a tile means you have
>    vision of it now (as opposed to knowing a tile which means you've seen it
>    before).  Note that a tile can be seen but not known (currently this only
>    happens when a city is founded with some unknown tiles in its radius); in
>    this case the tile is unknown (but map_get_seen will still return TRUE).
> ****************************************************************************/
> Is this in dispute?

No, not in dispute.  What is a bit tricky is that map_get_seen can
return TRUE for unknown tiles: this is a low-level function that
should only be used in a few places.

> > > P.S. Send future reports to the bug tracker.
> I *did* send the *report* to the tracker. Are you asking me to only send
> future *patches* for open/new tickets to the tracker and not the list?
> Do you want me to create a new ticket for each patch, like you
> apparently did to respond to my earlier message?

You sent the report to the tracker then sent the patch to the list.  I
erronously made a new report which I merged into the old once when I
realized it already existed (hence the ugly subject line).  Simply
responding to the email from the bug tracker (with PR# in the subject)
is generally sufficient for any reply.


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