Hi gophers, I want to know the reason behind the decision of using
*append(s[:0:0],
s...)* over the previous code since the two code return different slice
when dealing slice with zero len. The previous code will return brand new
slice with size zero, while the current code return an empty slice that's
still pointing to the previous array. And also, why not maybe using
*append(S(nil),
s...)* instead? This will return nil when dealing with zero len slice
though, but what's the potential problem that it will cause?
I don't know if this can be considered for a problem, but here is my
concern for the current code, *append(s[:0:0], s...)* :
If we try to create slices from an array pool to reduce allocation by using
append, and many our slices turned out to be zero, slices.Clone will return
slice that still pointing to array in the pool. If we try creating many of
them concurrently, (if I understand it correctly) the pool may try to
create many array objects as the object retrieved from Get may haven't been
Put back to the pool. Those array objects can only be garbage-collected
after those slices are no longer used / reachable and if it's an array of a
big struct, wouldn't it might potentially pressure the memory?
Here is just a pseudo-code for illustration only. I think the array
generated by pool will only be garbage-collected once *ch* is consumed and
the slices are no longer used:
var pool = sync.Pool{New: func() any { return &[255]bigstruct{} }}
var ch = make(chan []bigstruct, 1000)
for i := 0; i < 1000; i++ {
go func() {
arr := pool.Get().(*[255]bigstruct)
defer pool.Put(arr)
s := arr[:0]
ch <- slices.Clone(s) // slice points to arr
}()
}
CMIIW and thank you!
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