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Fix out of bounds in lighting subsystem (#75018)

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## About The Pull Request
Fixes #74697

Look at this for loop

https://github.com/tgstation/tgstation/blob/bfba2c59340a5cb2e5fe9eb4705a0c3ff5d6f407/code/controllers/subsystem/lighting.dm#L34-L39

Now look at update corners

https://github.com/tgstation/tgstation/blob/bfba2c59340a5cb2e5fe9eb4705a0c3ff5d6f407/code/modules/lighting/lighting_source.dm#L428-L430

Now look at refresh values. this proc has a chance to delete itself here

https://github.com/tgstation/tgstation/blob/bfba2c59340a5cb2e5fe9eb4705a0c3ff5d6f407/code/modules/lighting/lighting_source.dm#L315-L318
And here

https://github.com/tgstation/tgstation/blob/bfba2c59340a5cb2e5fe9eb4705a0c3ff5d6f407/code/modules/lighting/lighting_source.dm#L331-L334

Now look at the Destroy proc, specifically focus on the needs_update
condition

https://github.com/tgstation/tgstation/blob/bfba2c59340a5cb2e5fe9eb4705a0c3ff5d6f407/code/modules/lighting/lighting_source.dm#L66-L67

We are removing the light from the subsystem source queue while the
subsystem is still iterating through them causing big problems for this
for loop

https://github.com/tgstation/tgstation/blob/bfba2c59340a5cb2e5fe9eb4705a0c3ff5d6f407/code/controllers/subsystem/lighting.dm#L33-L37

which causes the out of bounds exception because loop variable `i` is
not updated accordingly when this list size is reduced mid iteration.

The solution? we have to move the loop variable `i` back whenever the
source is deleted i.e. removed from the list so we don't overflow

## Changelog

🆑
fix: out of bounds when updating lights in lighting subsystem
/🆑

---------

Co-authored-by: LemonInTheDark <58055496+LemonInTheDark@users.noreply.github.com>
This commit is contained in:
SyncIt21
2023-05-24 11:29:56 -07:00
committed by GitHub
co-authored by LemonInTheDark
parent fd777c6375
commit cd4ed228f2
2 changed files with 58 additions and 41 deletions
Download Patch File Download Diff File Expand all files Collapse all files
code/modules/lighting/lighting_source.dm
+11 -19
View File
@@ -434,28 +434,20 @@
var/list/datum/lighting_corner/new_corners = (corners - src.effect_str)
LAZYINITLIST(src.effect_str)
var/list/effect_str = src.effect_str
if (needs_update == LIGHTING_VIS_UPDATE)
for (var/datum/lighting_corner/corner as anything in new_corners)
for (var/datum/lighting_corner/corner as anything in new_corners)
APPLY_CORNER(corner)
if (. != 0)
LAZYADD(corner.affecting, src)
effect_str[corner] = .
// New corners are a subset of corners. so if they're both the same length, there are NO old corners!
if(needs_update != LIGHTING_VIS_UPDATE && length(corners) != length(new_corners))
for (var/datum/lighting_corner/corner as anything in corners - new_corners) // Existing corners
APPLY_CORNER(corner)
if (. != 0)
LAZYADD(corner.affecting, src)
effect_str[corner] = .
else
for (var/datum/lighting_corner/corner as anything in new_corners)
APPLY_CORNER(corner)
if (. != 0)
LAZYADD(corner.affecting, src)
effect_str[corner] = .
// New corners are a subset of corners. so if they're both the same length, there are NO old corners!
if(length(corners) != length(new_corners))
for (var/datum/lighting_corner/corner as anything in corners - new_corners) // Existing corners
APPLY_CORNER(corner)
if (. != 0)
effect_str[corner] = .
else
LAZYREMOVE(corner.affecting, src)
effect_str -= corner
else
LAZYREMOVE(corner.affecting, src)
effect_str -= corner
var/list/datum/lighting_corner/gone_corners = effect_str - corners
for (var/datum/lighting_corner/corner as anything in gone_corners)