test/fixedbugs/issue19743.go

// errorcheck -0 -m -l

// Copyright 2017 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.

package foo

// Escape analysis needs to treat the uintptr-typed reflect.*Header fields as pointers.

import (
	"reflect"
	"unsafe"
)

type immutableBytes []byte

// Bug was failure to leak param b.
func toString(b immutableBytes) string { // ERROR "leaking param: b$"
	var s string
	if len(b) == 0 {
		return s
	}

	strHeader := (*reflect.StringHeader)(unsafe.Pointer(&s))         // ERROR "toString &s does not escape$"
	strHeader.Data = (*reflect.SliceHeader)(unsafe.Pointer(&b)).Data // ERROR "toString &b does not escape$"

	l := len(b)
	strHeader.Len = l
	return s
}