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cmd/compile: ssa fails to flush return values during deferred func #14725

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rsc opened this issue Mar 9, 2016 · 2 comments
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cmd/compile: ssa fails to flush return values during deferred func #14725

rsc opened this issue Mar 9, 2016 · 2 comments
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Go1.7Early

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@rsc
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rsc commented Mar 9, 2016

Reduced from a bug in cmd/doc found by @robpike.
/cc @khr @dr2chase

The -ssa=0 behavior is correct: the program should print 1, not 0.

$ go run -gcflags -ssa=0 /tmp/x.go
1
$ go run /tmp/x.go
0
$ cat /tmp/x.go
package main

func main() {
    println(f())
}

func f() (x int) {
    for {
        defer func() {
            recover()
            x = 1
        }()
        panic(1)
    }
}
$
@rsc rsc added this to the Go1.7Early milestone Mar 9, 2016
@rsc rsc mentioned this issue Mar 9, 2016
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@randall77 randall77 mentioned this issue Mar 9, 2016
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@randall77 randall77 self-assigned this Mar 9, 2016
@randall77
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Upon further investigation, this seems unrelated to #14591. It looks like x is allocated on the heap and we never copy the heap value back to the stack at the end of the function (after deferreturn).

@gopherbot
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CL https://golang.org/cl/20486 mentions this issue.

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