mirror of
https://github.com/golang/go
synced 2024-11-23 04:10:04 -07:00
4efa216c9d
Allow the user to construct slices that are larger than the Go heap as long as they don't overflow the address space. Updates #48798. Change-Id: I659c8334d04676e1f253b9c3cd499eab9b9f989a Reviewed-on: https://go-review.googlesource.com/c/go/+/355489 Trust: Matthew Dempsky <mdempsky@google.com> Run-TryBot: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>
70 lines
1.5 KiB
Go
70 lines
1.5 KiB
Go
// run
|
|
|
|
// Copyright 2021 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 main
|
|
|
|
import (
|
|
"math"
|
|
"unsafe"
|
|
)
|
|
|
|
const maxUintptr = 1 << (8 * unsafe.Sizeof(uintptr(0)))
|
|
|
|
func main() {
|
|
var p [10]byte
|
|
|
|
// unsafe.Add
|
|
{
|
|
p1 := unsafe.Pointer(&p[1])
|
|
assert(unsafe.Add(p1, 1) == unsafe.Pointer(&p[2]))
|
|
assert(unsafe.Add(p1, -1) == unsafe.Pointer(&p[0]))
|
|
}
|
|
|
|
// unsafe.Slice
|
|
{
|
|
s := unsafe.Slice(&p[0], len(p))
|
|
assert(&s[0] == &p[0])
|
|
assert(len(s) == len(p))
|
|
assert(cap(s) == len(p))
|
|
|
|
// nil pointer with zero length returns nil
|
|
assert(unsafe.Slice((*int)(nil), 0) == nil)
|
|
|
|
// nil pointer with positive length panics
|
|
mustPanic(func() { _ = unsafe.Slice((*int)(nil), 1) })
|
|
|
|
// negative length
|
|
var neg int = -1
|
|
mustPanic(func() { _ = unsafe.Slice(new(byte), neg) })
|
|
|
|
// length too large
|
|
var tooBig uint64 = math.MaxUint64
|
|
mustPanic(func() { _ = unsafe.Slice(new(byte), tooBig) })
|
|
|
|
// size overflows address space
|
|
mustPanic(func() { _ = unsafe.Slice(new(uint64), maxUintptr/8) })
|
|
mustPanic(func() { _ = unsafe.Slice(new(uint64), maxUintptr/8+1) })
|
|
|
|
// sliced memory overflows address space
|
|
last := (*byte)(unsafe.Pointer(^uintptr(0)))
|
|
_ = unsafe.Slice(last, 1)
|
|
mustPanic(func() { _ = unsafe.Slice(last, 2) })
|
|
}
|
|
}
|
|
|
|
func assert(ok bool) {
|
|
if !ok {
|
|
panic("FAIL")
|
|
}
|
|
}
|
|
|
|
func mustPanic(f func()) {
|
|
defer func() {
|
|
assert(recover() != nil)
|
|
}()
|
|
f()
|
|
}
|