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// run
// Copyright 2019 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 30041: copying results of a reflect-generated
// call on stack should not have write barrier.
package main
import (
"reflect"
"runtime"
"unsafe"
)
var badPtr uintptr
var sink []byte
func init() {
// Allocate large enough to use largeAlloc.
b := make([]byte, 1<<16-1)
sink = b // force heap allocation
// Any space between the object and the end of page is invalid to point to.
badPtr = uintptr(unsafe.Pointer(&b[len(b)-1])) + 1
}
type ft func() *int
var fn ft
func rf([]reflect.Value) []reflect.Value {
a := reflect.ValueOf((*int)(nil))
return []reflect.Value{a}
}
const N = 1000
func main() {
fn = reflect.MakeFunc(reflect.TypeOf(fn), rf).Interface().(ft)
// Keep running GC so the write barrier is on.
go func() {
for i := 0; i < N; i++ {
runtime.GC()
}
}()
var x [10]uintptr
for i := range x {
x[i] = badPtr
}
for i := 0; i < N; i++ {
runtime.Gosched()
use(x) // prepare bad pointers on stack
fn()
}
}
//go:noinline
func use([10]uintptr) {}
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