Volker,
I don't know if the term "memory leak" is misuse.
But, the 1st version's memory usage is constant but the 2nd version's one
grows over time as if nothing is garbage-collected.
Yota
On Friday, March 3, 2017 at 2:38:08 AM UTC+9, Volker Dobler wrote:
>
> Am Donnerstag, 2. März 2017 17:15:05 UTC+1 schrieb Yota Toyama:
>>
>> Hi, all.
>>
>> I'm trying to understand argument liveness in Go 1.8.
>> As preparation for it, I wrote 2 programs which iterate over infinite
>> lists.
>> At first, I thought both can be run forever without any memory leak.
>> However, the result was that one could and the other couldn't.
>>
>> Their main difference is the way to iterate lists.
>>
>> l := *NewList(42, nil)
>>
>> for {
>> l = *l.Rest() // Cause no memory leak :)
>> }
>>
>> vs
>>
>> l := NewList(42, nil)
>>
>> for {
>> l = l.Rest() // Cause memory leak!!!
>> }
>>
>> The repository is here <https://github.com/raviqqe/argument-liveness.go>.
>> I wanna understand why the latter causes memory leak and what is going on
>> in my programs at low level.
>> Any ideas?
>>
>
>
> What makes you say that one version causes a memory leak?
>
> The first version produces much less garbage (well, basically none):
> l is a ListValue and the freshly created "list rest" is assigned to it,
> basically just overwriting the memory location of l with the same
> value.
>
> The second version produces an endless linked list where only the
> last list element is reachable from your code as this is the only value
> you have a pointer to.
>
> So the second produces tremendous amounts of garbage but this
> garbage is collectable. Running it shows no problem when tracing GC
> at least not with Go 1.8.
>
> So the main difference is: The first code does not produce an "endless
> list" it just operates on one List value while the second code really
> constructs an ever increasing linked list if List values where only the
> tail is reachable/uncollectable.
>
> How did you determine the second version "leaks"?
>
> V
>
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