Some temporary lists that are a result of list operations with some built in procs (view, range, viewers, etc.) are kept alive even after the proc ends, and as such keep the objects they contain alive until the list is cleared when another similar loop construct is called.
Numbered Steps to Reproduce Problem:
1. Do a for(var/O in view(n) - someValue) while making sure there are atoms that view can return
2. Clear all the references you can that keep the atoms from the view call alive
3. The atoms don't get garbage collected as there's still a list keeping them alive
Code Snippet (if applicable) to Reproduce Problem:
atom/movable
Del()
world.log << "deleting [src] ([ref(src)])"
..()
mob
verb
DoBugView() // calling it once keeps the newly created objects alive even after the proc ends, calling it a second time clears the previous temporary list and releases the references to those objects which calls their Del() procs
for(var/turf/T in view(2))
var/obj/O = new(T)
O.name = "bugView"
for(var/obj/O in view(2) - src)
O.loc = null
DoBugRange() // same as the view version
for(var/turf/T in range(2))
var/obj/O = new(T)
O.name = "bugRange"
for(var/obj/O in range(2) - src)
O.loc = null
DoBugViewers() // same as the view version
for(var/turf/T in view(2))
var/mob/M = new(T)
M.name = "bugViewers"
for(var/mob/M in viewers(2) - src)
M.loc = null
ClearLastList() // calling this after calling any of the previous verbs releases the hidden temporary list and its contents
for(var/V in view() - 1)
V
CheckObjs() // used to see how many objs are kept alive
world << "Outputing objs"
for(var/obj/O)
world << O
world << "Done"
CheckMobs() // used to see how many mobs are kept alive
world << "Outputing mobs"
for(var/mob/M)
world << M
world << "Done"
Expected Results:
All temporary lists are released by the time the proc ends, so any items they contain can be properly garbage collected when needed.
Actual Results:
Sometimes a temporary list is kept alive even after a proc ends and through multiple other proc calls.
Does the problem occur:
Every time? Or how often? Every time
In other games? Yes
In other user accounts? Yes
On other computers? Yes
When does the problem NOT occur?
When list operations are not used as a direct statement in a loop setup.
Did the problem NOT occur in any earlier versions? If so, what was the last version that worked? (Visit http://www.byond.com/download/build to download old versions for testing.)
Tested in 513.1542, 514.1589 and 515.1597, same result.
Workarounds:
Instead of doing for(var/O in view(n) - someValue) store the resulting list in a variable:
var/myList = view(n) - someValue
for(var/O in myList) ...
