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cmd/gc: returning a function parameter causes escape #3702

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bradfitz opened this issue Jun 4, 2012 · 6 comments
Closed

cmd/gc: returning a function parameter causes escape #3702

bradfitz opened this issue Jun 4, 2012 · 6 comments
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@bradfitz
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bradfitz commented Jun 4, 2012

The buf below shouldn't escape to the heap.

package main

func nothing() {
}

func f(b []byte) []byte { // leaking param: b
        b[0] = 'H'
        b[1] = 'i'
        nothing() // (force f to not inline.)
        return b[:2]
}

func main() {
        var buf [10]byte // moved to heap: buf
        hi := f(buf[:]) // buf escapes to heap
        for i, c := range hi {
                println(i, c)
        }
}

$ go tool 6g -s -m e.go
e.go:3: can inline nothing
e.go:9: inlining call to nothing
e.go:14: moved to heap: buf
e.go:6: leaking param: b
e.go:15: buf escapes to heap
@rsc
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rsc commented Jun 4, 2012

Comment 1:

That is exactly what I'm working on. I am probably going to have to
change gears for a week or two, but it's at the top of my compiler
work list.

Status changed to Accepted.

@rsc
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rsc commented Sep 12, 2012

Comment 2:

http://golang.org/cl/6339053/ is supposed to fix this. lvd may look into why
it's broken, or if he doesn't get to it I will.

@rsc
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rsc commented Sep 12, 2012

Comment 3:

Labels changed: added priority-later, removed priority-triage.

@rsc
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rsc commented Sep 12, 2012

Comment 4:

Labels changed: added go1.1.

@lvdlvd
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lvdlvd commented Oct 29, 2012

@bradfitz
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bradfitz commented Oct 29, 2012

Comment 6:

Verified the example at top doesn't example.

Status changed to Fixed.

Attachments:

  1. e.go (731 bytes)

@rsc rsc added this to the Go1.1 milestone Apr 14, 2015
@rsc rsc removed the go1.1 label Apr 14, 2015
@golang golang locked and limited conversation to collaborators Jun 24, 2016
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