go issue19078 源码
golang issue19078 代码
文件路径：/test/fixedbugs/issue19078.go
// run
// 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.
// Issue 19078: liveness & zero-initialization of results
// when there is a defer.
package main
import "unsafe"
func main() {
// Construct an invalid pointer. We do this by
// making a pointer which points to the unused space
// between the last 48-byte object in a span and the
// end of the span (there are 32 unused bytes there).
p := new([48]byte) // make a 48-byte object
sink = &p // escape it, so it allocates for real
u := uintptr(unsafe.Pointer(p)) // get its address
u = u >> 13 << 13 // round down to page size
u += 1<<13 - 1 // add almost a page
for i := 0; i < 1000000; i++ {
_ = identity(u) // installs u at return slot
_ = liveReturnSlot(nil) // incorrectly marks return slot as live
}
}
//go:noinline
func liveReturnSlot(x *int) *int {
defer func() {}() // causes return slot to be marked live
sink = &x // causes x to be moved to the heap, triggering allocation
return x
}
//go:noinline
func identity(x uintptr) uintptr {
return x
}
var sink interface{}
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