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all: assign zero after resize in implementations of heap.Interface #26296

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merged 1 commit into from
Dec 5, 2022
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all: assign zero after resize in implementations of heap.Interface #26296

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1 change: 1 addition & 0 deletions core/txpool/list.go
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ func (h *nonceHeap) Pop() interface{} {
old := *h
n := len(old)
x := old[n-1]
old[n-1] = 0
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Setting a uint64 to 0 does not make any difference to the gc

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Slice tricks from the Go wiki states that you should set the item that is deleted to the zero value of T.

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Interesting!

*h = old[0 : n-1]
return x
}
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1 change: 1 addition & 0 deletions core/types/transaction.go
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Expand Up @@ -508,6 +508,7 @@ func (s *TxByPriceAndTime) Pop() interface{} {
old := *s
n := len(old)
x := old[n-1]
old[n-1] = nil
*s = old[0 : n-1]
Comment on lines +511 to 512
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Interesting idea -- but I think this should not be needed. Instead of nilling the item, we resize the slice.

Taken to the extreme, imagine we have a slice with 100 pointers, and then do myslice = myslice[:0] -- that should free up all the pointers for the gc, without us explicitly nilling them. It's the same case here.

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I don't think resizing would help since the same underlying array is referenced.

This is the example for a priority queue from the standard lib:

func (pq *PriorityQueue) Pop() any {
	old := *pq
	n := len(old)
	item := old[n-1]
	old[n-1] = nil  // avoid memory leak
	item.index = -1 // for safety
	*pq = old[0 : n-1]
	return item
}

https://pkg.go.dev/container/heap

return x
}
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1 change: 1 addition & 0 deletions p2p/util.go
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Expand Up @@ -70,6 +70,7 @@ func (h *expHeap) Pop() interface{} {
old := *h
n := len(old)
x := old[n-1]
old[n-1] = expItem{}
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IMO this is moot, and will be forgotten by the next line

*h = old[0 : n-1]
return x
}