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[Bryan Derksen]

I'm doing some extensive above-ground wall-building in my current game and I noticed that two particular tiles kept getting their wall construction suspended. I tried all sorts of ways to get dwarves to build wall segments there, but after almost finishing they'd always suspend again with a 'creature occupying space' message (there was no sign of any creature there). I eventually tried building doors there and they were constructed successfully, but remained permanently open as if there was something in them. At a complete loss, I turned to Tweak's tile editor to analyze the situation. For both of those tiles, the 02 and 04 occupancy flags were checked, both of which are listed as "unknown" in Tweak. 03, the creature occupancy flag, wasn't set. Using Tweak to unflag 02 had no effect, but unflagging 04 made the door shut - I assume this is the occupancy flag that was causing problems. I don't like using Tweak this way because it often permanently sets the temperature of tiles it tampers with to 0, killing any dwarf that passes through. Seems to have avoided that this time though.

I have no idea what caused these particular tiles to get flagged this way. I can provide saves if needed, but since I don't know when this happened I have no idea if any of my saves are of particular use.

[Toady One]

Might be the grounded unit occupancy flag, which comes after the regular unit occupancy flag.  But yeah, a post-problem save won't help.  I'm not sure why it happened, if you weren't using utilities beforehand.

[Bryan Derksen]

As far as I'm aware that bit of troubleshooting was the first time I used an external editor on that fort. Not even Dwarf Foreman (hasn't been compatible lately and the fort's a recent start).

Ah well, it seems like a pretty rare thing - I've been doing a lot of constructing and only those two tiles have cropped up like that.

[Hyndis]

I've had this happen even back in 38c, but its so rare I have no idea how to reproduce the bug, and I didn't think to get a save when it happened back then.

I've had it happen in almost every version since then, but again, its an extremely rare (though sometimes aggravating) bug. I'll try to remember to get a save of it if it happens again.

[Raumkraut]

Perhaps related to the problem reported in the eternal construction thread?
Although in that instance the walls didn't get suspended, they were just never finished. Same glitch, different occupancy flag maybe?

[Bizarro Kale]

I have been experiencing this bug in v0.28.181.39f, no external applications or game modifications - with the exception of a tileset and init options, have been used.

Several locations are producing a "cancels Construct Building: Creature occupying site." announcement when attempting to construct certain objects, including: Wall, Fortification, Statue.
This effect remains no matter how many attempts are made to construct the above items, always with the same message.

This problem persists when saving the game and re-loading. Also when restarting the executable and reloading.
Channeling the tile does not remove the problem, nor does attempting to "Dump" the empty tile.

It is still possible to construct (and deconstruct) a number of different items, such as: Floor, Ramp, Up Stair, Down Stair, Up/Down Stair, Cage, Cabinet, Quern, Archery Target.
Also possible are: Floodgate (Constructs closed and opens as normal, refuses to close after opening)
Door (Remains open from the moment it is constructed, presumably it would construct closed if the dwarf didn't need to be inside the tile to build it)
Bridge (Operates as normal, the bug remains after attempting to "squash" the imaginary creature by lowering the bridge.

These locations are generally 1x1 areas, I have encountered several in the space of a single z level on a 2x2 map. So far attempting to construct in the surrounding tiles is always successful, however I think it is possible to encounter several of these tiles together given the right circumstances.

I have only encountered them on the ground level (0 on the top right indicator), however I haven't done much wall contruction on other levels yet.

Abandoning and reclaiming your fortress -does- clear this bug and allows you to build as normal.

<section removed, see later post>

[Exponent]

Do you by any chances have seasonal autosaves, one of which that does not have this problem?  If you could figure out what happened between such an autosave and the next one to cause this, it could be of immense use.  As it is, Toady has already had access to a few saves that are experiencing the problem, but without knowing what happened to cause the problem, a save doesn't help him much.

[Bizarro Kale]

UPDATE: This bug has been reproduced successfully, a save file prior to the bug has been provided, follow the instructions for Test2 to reproduce it.

I'm going to run some tests on a new fortress and hopefully get a before and after save.

However, reading that other thread linked by Raumkraut I saw it mentioned that people had thought it was caused by the trade depot, I did previously have a trade depot in the location of the above bugged tiles.

I'm thinking it might have something to do with caged creatures dying at the trade depot, as I've noticed my purchased cages don't get moved very quickly and the ones I saw in my stockpile had dead creatures in them.

Test1:
-Test depot area for bug
-Build depot on unbugged area
-Deconstruct depot
-Test depot area for bug
Result: No bug

Test2:
-Test depot area for bug
-Build depot on unbugged area
-Wait for traders
-Traders leave
-Deconstruct depot
-Test depot area for bug
Result: BUGGED
Notes: This could be caused by the merchants, caravans, merchant animals or trade animals in cages.
The merchants in my test case brought all of the above, no attempt to open the trade window was made, no goods were moved there and no traderdwarf was sent to the depot.

Test3:
-Test depot area for bug
-Build depot on unbugged area
-Wait for traders
-Trade for all animals in cages
-Traders leave
-Deconstruct depot with cages in it
-Test depot area for bug
Result: BUGGED
Notes: This could be caused by the merchants, caravans, merchant animals or trade animals in cages.
The merchants in my test case brought all of the above, purchasing anything from the caravan is unneccesary.

Test4:
-Test depot area for bug
-Build depot on unbugged area
-Wait for traders
-Trade for animals in cages
-Traders leave
-Wait for caged animals to die
-Deconstruct depot with cages in it
-Test depot area for bug
Result: Test not needed

Test5:
-Test cage area for bug
-Build cage on unbugged area
-Deconstruct cage
-Test cage area for bug
Result: No bug

Test6:
-Test cage area for bug
-Build cage on unbugged area
-Place animal in cage
-Deconstruct cage
-Test cage area for bug
Result: No bug

Test7:
-Test cage area for bug
-Place unbuilt cage with animal on unbugged area
-Move cage
-Test cage area for bug
Result: No bug

Test8:
-Test cage area for bug
-Build cage on unbugged area
-Place animal in cage
-Wait for caged animal to die
-Deconstruct cage
-Test cage area for bug
Result: Test not needed

Test9:
-Test cage area for bug
-Place unbuilt cage with animal on unbugged area
-Wait for caged animal to die
-Test cage area for bug
Result: Test not needed


I have reproduced this bug, Test 2 produced the important results.
This bug is caused by traders visiting the trade depot, whether the merchants, caravans, merchant animals or trade animals in cages are the cause is unclear, but they are the most likely cases.
The bug is not triggered until the merchants unload their goods and/or load them up again at the depot, as dismantling the depot before the traders are able to reach it will prevent the bug from happening, even though the caravans move to the same position regardless.
It is this behaviour that leads me to believe the bug is caused by loading/unloading, most likely of caged animals, in the depot.
Purchasing all animals and moving them during construction still leaves the vacated tiles bugged.

Here is a save file made just before the bug occurs, the message regarding inbound traders has just occurred and auto-paused.
http://files.filefront.com/pre+bugzip/;11494797;/fileinfo.html

[Exponent]

Excellent work.  Maybe Toady will see this and can use this information to fix the bug.  Granted, it's not the hugest bug in the world, but hopefully this info can make it easy to track the bug down and squash it.

[Bizarro Kale]

Bug still present in 40a


-edit- Confirmed fixed in 40b

[Toady One]

Okay, the wagons weren't cleaning up their mess properly when they left the depot.  Should be fixed for next time.  Thanks for the recipe.