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// run
// Copyright 2018 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.
// Make sure return values aren't scanned until they
// are initialized, when calling functions and methods
// via reflect.
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
}
func f(d func() *byte) *byte {
// Initialize callee args section with a bad pointer.
g(badPtr)
// Then call a function which returns a pointer.
// That return slot starts out holding a bad pointer.
return d()
}
//go:noinline
func g(x uintptr) {
}
type T struct {
}
func (t *T) Foo() *byte {
runtime.GC()
return nil
}
func main() {
// Functions
d := reflect.MakeFunc(reflect.TypeOf(func() *byte { return nil }),
func(args []reflect.Value) []reflect.Value {
runtime.GC()
return []reflect.Value{reflect.ValueOf((*byte)(nil))}
}).Interface().(func() *byte)
f(d)
// Methods
e := reflect.ValueOf(&T{}).Method(0).Interface().(func() *byte)
f(e)
}
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