Antares
Spell Reviewer
- Joined
- Dec 13, 2009
- Messages
- 920
Hello,
I'm again and again running into situations where I'm unsure how the Lua garbage collector would handle things and how I should write my code to prevent unexpected behavior.
I've just had ChatGPT explain to me how the Lua garbage collector determines whether a closure where objects are used in is still reachable or not, and therefore determine whether objects referenced within those closures should be garbage collected.
"In Lua, the garbage collector uses a form of reachability analysis to determine whether an object (including closures and their upvalues) is reachable or not. Objects are considered reachable if they are part of the root set or if they can be reached through a chain of references starting from the root set.
The root set typically includes global variables, local variables in currently executing functions, and other objects that the collector knows are reachable. During the garbage collection process, Lua's collector traces the objects starting from the root set and follows references from one object to another."
Which leads me to the question... is the Lua garbage collector smart enough to take triggers and timers into account when determining which code is still reachable?
Here, we create a table with some numbers in it. If we disregard the timer, the table should quickly be garbage collected because it is defined as a local variable and is out of scope as the code exits the function CreateNumbers. The anonymous callback function is also only defined within CreateNumbers and becomes out of scope. This should make the table be cleaned unless the garbage collector is smart enough to realize that it is still referenced by a function used by the currently running timer, but I'm doubtful that it understands what the Warcraft III natives are doing.
Please correct me if I'm wrong and if I'm not, how would one write the above code to prevent premature garbage collection?
I'm again and again running into situations where I'm unsure how the Lua garbage collector would handle things and how I should write my code to prevent unexpected behavior.
I've just had ChatGPT explain to me how the Lua garbage collector determines whether a closure where objects are used in is still reachable or not, and therefore determine whether objects referenced within those closures should be garbage collected.
"In Lua, the garbage collector uses a form of reachability analysis to determine whether an object (including closures and their upvalues) is reachable or not. Objects are considered reachable if they are part of the root set or if they can be reached through a chain of references starting from the root set.
The root set typically includes global variables, local variables in currently executing functions, and other objects that the collector knows are reachable. During the garbage collection process, Lua's collector traces the objects starting from the root set and follows references from one object to another."
Which leads me to the question... is the Lua garbage collector smart enough to take triggers and timers into account when determining which code is still reachable?
Lua:
function CreateNumbers()
local numbers = {1, 3, 5}
local newTimer = CreateTimer()
TimerStart( newTimer, 10, false, function()
print(numbers[1] + numbers[2] + numbers[3])
end)
end
Here, we create a table with some numbers in it. If we disregard the timer, the table should quickly be garbage collected because it is defined as a local variable and is out of scope as the code exits the function CreateNumbers. The anonymous callback function is also only defined within CreateNumbers and becomes out of scope. This should make the table be cleaned unless the garbage collector is smart enough to realize that it is still referenced by a function used by the currently running timer, but I'm doubtful that it understands what the Warcraft III natives are doing.
Please correct me if I'm wrong and if I'm not, how would one write the above code to prevent premature garbage collection?