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runtime: document that KeepAlive doesn't have anything to do with unsafe.Pointer safety rules #47562

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mdempsky opened this issue Aug 5, 2021 · 1 comment · Fixed by ferrmin/go#122
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runtime: document that KeepAlive doesn't have anything to do with unsafe.Pointer safety rules #47562

mdempsky opened this issue Aug 5, 2021 · 1 comment · Fixed by ferrmin/go#122
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Documentation FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.17

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@mdempsky
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mdempsky commented Aug 5, 2021

There's nothing in the runtime.KeepAlive or unsafe.Pointer documentation to suggest they interact, but I've seen experienced Go engineers mistakenly interpret that runtime.KeepAlive can be used as a quick-fix for working around misuse of unsafe.Pointer.

This often happens to work today, but it's not guaranteed to be safe. In particular, misuse of unsafe.Pointer can lead to objects being allocated on the stack, which can result in unintended program behavior due to memory corruption: https://play.golang.org/p/s2G90hvQUOZ

We don't normally document what things aren't used for, but this seems like a subtle enough point to call out, IMO.
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Change https://golang.org/cl/340269 mentions this issue: runtime: warn that KeepAlive is not an unsafe.Pointer workaround

@dmitshur dmitshur added the NeedsFix The path to resolution is known, but the work has not been done. label Aug 5, 2021
@dmitshur dmitshur added this to the Go1.17 milestone Aug 5, 2021
@ferrmin ferrmin mentioned this issue Aug 6, 2021
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@cristaloleg cristaloleg mentioned this issue Sep 18, 2021
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runtime: warn that KeepAlive is not an unsafe.Pointer workaround golang/go
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