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// run
// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Issue 8048. Incorrect handling of liveness when walking stack
// containing faulting frame.
package main
import "runtime"
func main() {
test1()
test2()
test3()
}
func test1() {
// test1f will panic without its own defer.
// The runtime.GC checks that we can walk the stack
// at that point and not get confused.
// The recover lets test1 exit normally.
defer func() {
runtime.GC()
recover()
}()
test1f()
}
func test1f() {
// Because b == false, the if does not execute,
// so x == nil, so the println(*x) faults reading
// from nil. The compiler will lay out the code
// so that the if body occurs above the *x,
// so if the liveness info at the *x is used, it will
// find the liveness at the call to runtime.GC.
// It will think y is live, but y is uninitialized,
// and the runtime will crash detecting a bad slice.
// The runtime should see that there are no defers
// corresponding to this panicked frame and ignore
// the frame entirely.
var x *int
var b bool
if b {
y := make([]int, 1)
runtime.GC()
x = &y[0]
}
println(*x)
}
func test2() {
// Same as test1, but the fault happens in the function with the defer.
// The runtime should see the defer and garbage collect the frame
// as if the PC were immediately after the defer statement.
defer func() {
runtime.GC()
recover()
}()
var x *int
var b bool
if b {
y := make([]int, 1)
runtime.GC()
x = &y[0]
}
println(*x)
}
func test3() {
// Like test1 but avoid array index, which does not
// move to end of function on ARM.
defer func() {
runtime.GC()
recover()
}()
test3setup()
test3f()
}
func test3setup() {
var x uintptr
var b bool
b = true
if b {
y := uintptr(123)
runtime.GC()
x = y
}
runtime.GC()
globl = x
}
var globl uintptr
func test3f() {
var x *int
var b bool
if b {
y := new(int)
runtime.GC()
x = y
}
println(*x)
}
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