package main

import (
    "fmt"
    "runtime"
)

var sink *[20]byte

func f() (x [20]byte) {
    // Force x to be allocated on the heap.
    sink = &x
    sink = nil

    // Go to deferreturn after the panic below.
    defer func() {
        recover()
    }()

    // This call collects the heap-allocated version of x (!)
    runtime.GC()

    // Allocate that same object again and clobber it.
    y := new([20]byte)
    for i := 0; i < 20; i++ {
        y[i] = 99
    }
    // Make sure y is heap allocated.
    sink = y

    panic(nil)

    // After the recover we reach the deferreturn, which
    // copies the heap version of x back to the stack.
    // It gets the pointer to x from a stack slot that was
    // not marked as live during the call to runtime.GC().
}
func main() {
    x := f()
    for _, v := range x {
        if v != 0 {
            fmt.Printf("%v\n", x)
            panic("bad")
        }
    }
}