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0 pointsknorker3mo ago0 comments

Yeah. That's what I said.

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I mean that escape analysis has nothing to do with my example either, in terms of understand the semantics of the code (so I’m disagreeing with the ‘because GC and escape analysis’ part of your comment).

knorkerOP3mo ago

Your https://news.ycombinator.com/item?id=46234206 relies on escape analysis though, right?

Escape analysis is the reason your `x` is on the heap. Because it escaped. Otherwise it'd be on the stack.[1]

Now if by "semantics of the code" you mean "just pretend everything is on the heap, and you won't need to think about escape analysis", then sure.

Now in terms of what actually happens, your code triggers escape analysis, and OP does not.

[1] Well, another way to say this I guess is that without escape analysis, a language would be forced to never use the stack.

foldr3mo ago

Escape analysis clearly isn’t part of the semantics of Go. For that to be the case, the language standard would have to specify exactly which values are guaranteed to be stack allocated. In reality, this depends on size thresholds which can vary from platform to platform or between different versions of the Go compiler. Is the following non-escaping array value stack allocated?

    func pointless() byte {
        var a byte[1024]
        a[0] = 1
        return a[0]
    }

That’s entirely up to the compiler, not something that’s determined by the language semantics. It could vary from platform to platform or compiler version to compiler version. So clearly you don’t need to think about the details of escape analysis to understand what your code does because in many cases you simply won’t know if your value is on the stack or not.

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foldr3mo ago

knorkerOP3mo ago

Your https://news.ycombinator.com/item?id=46234206 relies on escape analysis though, right?

Escape analysis is the reason your `x` is on the heap. Because it escaped. Otherwise it'd be on the stack.[1]

Now if by "semantics of the code" you mean "just pretend everything is on the heap, and you won't need to think about escape analysis", then sure.

Now in terms of what actually happens, your code triggers escape analysis, and OP does not.

[1] Well, another way to say this I guess is that without escape analysis, a language would be forced to never use the stack.

foldr3mo ago

    func pointless() byte {
        var a byte[1024]
        a[0] = 1
        return a[0]
    }

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j / k navigate · click thread line to collapse