alt Hacker NewsAre you sure this is what's happening? Looks to me like the slice object is returned by value, and the array was always on the heap. See https://go.dev/play/p/Bez0BgRny7G (the address of the slice object changed, so it's not the same object on the heap)
Sure, Go has escape analysis, but is that really what's happening here?
Isn't this a better example of escape analysis: https://go.dev/play/p/qX4aWnnwQV2 (the object retains its address, always on the heap, in both caller and callee)
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That’s the one.
Since 1.17 it’s not impossible for escape analysis to come into play for slices but afaik that is only a consideration for slices with a statically known size under 64KiB.
Interesting! This could be true. I'll play around with this in a bit.
Yes, this is merely the slice fat pointer being copied and returned.
Depending on escape analysis, the array underlying the slice can get allocated on the stack as well, if it doesn't escape the function context. Of course, in this case, because we are returning a pointer to it via the slice, that optimization isn't applicable.