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Splizard / minetest-mod-snow

Adds snow biomes to Minetest.
http://splizard.com/minetest/mods/snow-biomes/
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Unusual error and crash. #20

Closed jhcole closed 8 years ago

jhcole commented 8 years ago

Running 90e08fe. I can't figure out how line falling_snow.lua:98 is fine but then it chokes on 109. I've only seen this error once.

2016-08-10 04:17:41: ERROR[Main]: ServerError: Runtime error from mod 'snow' in callback environment_Step(): /home/foz/.minetest/mods/snow/src/falling_snow.lua:109: attempt to index a nil value 2016-08-10 04:17:41: ERROR[Main]: stack traceback: 2016-08-10 04:17:41: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:109: in function 'cold_perlin_test' 2016-08-10 04:17:41: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:137: in function 'get_snow' 2016-08-10 04:17:41: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:226: in function 'step_func' 2016-08-10 04:17:41: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:274: in function </home/foz/.minetest/mods/snow/src/falling_snow.lua:273> 2016-08-10 04:17:41: ERROR[Main]: /usr/local/share/minetest/builtin/game/register.lua:369: in function </usr/local/share/minetest/builtin/game/register.lua:349>

HybridDog commented 8 years ago

https://github.com/Splizard/minetest-mod-snow/blob/90e08fe0bca00065f92e63f7f166e7ba35baa993/src/falling_snow.lua#L88

The metatable of cold_perl_values is changed, maybe the garbage collector deleted cold_perl_values[y] when minetest.get_perlin took memory. Actually it should know that cold_perl_values[y][x] is accessed there and avoid deleting it, shouldn't it?

jhcole commented 8 years ago

I thought it might be related to garbage collection, but I would have hoped Lua would know better. Its very confusing to me at the moment what happened.

jhcole commented 8 years ago

It happened again :(

2016-08-14 13:34:58: ERROR[Main]: ServerError: Runtime error from mod 'snow' in callback environment_Step(): /home/foz/.minetest/mods/snow/src/falling_snow.lua:109: attempt to index a nil value 2016-08-14 13:34:58: ERROR[Main]: stack traceback: 2016-08-14 13:34:58: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:109: in function 'cold_perlin_test' 2016-08-14 13:34:58: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:137: in function 'get_snow' 2016-08-14 13:34:58: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:226: in function 'step_func' 2016-08-14 13:34:58: ERROR[Main]: /home/foz/.minetest/mods/snow/src/falling_snow.lua:274: in function </home/foz/.minetest/mods/snow/src/falling_snow.lua:273> 2016-08-14 13:34:58: ERROR[Main]: /usr/local/share/minetest/builtin/game/register.lua:369: in function </usr/local/share/minetest/builtin/game/register.lua:349>

HybridDog commented 8 years ago

Maybe minetest.get_perlin takes lots of memory. l now assume the garbage collector does not know that it is used there. Anyway, if it removes cold_perl_values[y], it needs memory, so it should not cache v if it happened: https://github.com/Splizard/minetest-mod-snow/commit/30b0dd9557aa72ca787d108424e90e8969df0641

Strangely your error message is attempt to index a nil value, i.e. x or y is nil (somehow?) but if the field was nil, e.g. due to garbage collection, the error message would be different: attempt to index field '?' (a nil value). If it still crashes, it now tells at least if y (or both) (L109) or only x (L110) becomes nil, please inform me.

rubenwardy commented 8 years ago

try adding

if x == nil then
    error("nil x")
end
if y == nil then
    error("ni y")
end

to https://github.com/Splizard/minetest-mod-snow/blob/90e08fe0bca00065f92e63f7f166e7ba35baa993/src/falling_snow.lua#L97

and seeing if that causes it to crash due to either of them being nil

HybridDog commented 8 years ago

rubenwardy, as long as this can't be reproduced, the code doesn't help much

x and y is passed to l_get2d, which copies the values to NoisePerlin2D l assume

HybridDog commented 8 years ago

but this crashes as soon as a the first player joins the server.

2016-08-20 06:23:59: ERROR[Main]: ServerError: Runtime error from mod 'snow' in callback environment_Step(): .../foz/Code/minetest/bin/../mods/snow/src/falling_snow.lua:122: x no integer but 38.588001251221 y no integer but -43.385997772217 2016-08-20 06:23:59: ERROR[Main]: stack traceback: 2016-08-20 06:23:59: ERROR[Main]: [C]: in function 'error' 2016-08-20 06:23:59: ERROR[Main]: .../foz/Code/minetest/bin/../mods/snow/src/falling_snow.lua:122: in function 'cold_perlin_test' 2016-08-20 06:23:59: ERROR[Main]: .../foz/Code/minetest/bin/../mods/snow/src/falling_snow.lua:155: in function 'get_snow' 2016-08-20 06:23:59: ERROR[Main]: .../foz/Code/minetest/bin/../mods/snow/src/falling_snow.lua:244: in function 'step_func' 2016-08-20 06:23:59: ERROR[Main]: .../foz/Code/minetest/bin/../mods/snow/src/falling_snow.lua:292: in function <.../foz/Code/minetest/bin/../mods/snow/src/falling_snow.lua:291> 2016-08-20 06:23:59: ERROR[Main]: /home/foz/Code/minetest/bin/../builtin/game/register.lua:369: in function

l think l forgot to round the player position, so the cache didn't work and l assume because float numbers are inaccurate in lua, the indices change slightly.

jhcole commented 8 years ago

I deployed the latest (b1a7d12) a week ago and haven't seen it happen again so hopefully it is fixed. I have, however, run out of memory twice in the last week #22