panic: unaligned 64-bit atomic operation

[zllovesuki]

attempting to use skipmap on an arm build (with GOARM=7, GOARCH=arm, go version 1.17.8) gave such panic:

panic: unaligned 64-bit atomic operation

goroutine 1 [running]:
runtime/internal/atomic.panicUnaligned()
        /usr/local/go/src/runtime/internal/atomic/unaligned.go:8 +0x24
runtime/internal/atomic.Load64(0xd3e9cc)
        /usr/local/go/src/runtime/internal/atomic/atomic_arm.s:286 +0x14
github.com/zhangyunhao116/skipmap.(*StringMap).randomlevel(0xd3e9c0)
        /home/rachel/go/pkg/mod/github.com/zhangyunhao116/skipmap@v0.7.0/types.go:8919 +0x34
github.com/zhangyunhao116/skipmap.(*StringMap).LoadOrStoreLazy(0xd3e9c0, {0xd21270, 0xf}, 0x541ca8)
        /home/rachel/go/pkg/mod/github.com/zhangyunhao116/skipmap@v0.7.0/types.go:9081 +0x20

skipmap version is v0.7.0 as i'm on go <1.18

Perhaps we can add some padding around these fields? or maybe rearrange the fields so they are aligned:

// StringMap represents a map based on skip list.
type StringMap struct {
	header       *stringNode
	length       int64
	highestLevel int64 // highest level for now
}

... and for the nodes

[zhangyunhao116]

Thanks for reporting this issue!
The problem has been fixed in branch oldversion. We can use go get github.com/zhangyunhao116/skipmap@oldversion to reinstall it. (This problem does not exist if version >= v0.8.0)

[zllovesuki]

I can confirm that moving fields around fixed the panic.