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https://github.com/golang/go
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2c423f063b
A few examples (for accessing a slice of length 3): s[-1] runtime error: index out of range [-1] s[3] runtime error: index out of range [3] with length 3 s[-1:0] runtime error: slice bounds out of range [-1:] s[3:0] runtime error: slice bounds out of range [3:0] s[3:-1] runtime error: slice bounds out of range [:-1] s[3:4] runtime error: slice bounds out of range [:4] with capacity 3 s[0:3:4] runtime error: slice bounds out of range [::4] with capacity 3 Note that in cases where there are multiple things wrong with the indexes (e.g. s[3:-1]), we report one of those errors kind of arbitrarily, currently the rightmost one. An exhaustive set of examples is in issue30116[u].out in the CL. The message text has the same prefix as the old message text. That leads to slightly awkward phrasing but hopefully minimizes the chance that code depending on the error text will break. Increases the size of the go binary by 0.5% (amd64). The panic functions take arguments in registers in order to keep the size of the compiled code as small as possible. Fixes #30116 Change-Id: Idb99a827b7888822ca34c240eca87b7e44a04fdd Reviewed-on: https://go-review.googlesource.com/c/go/+/161477 Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>
133 lines
3.2 KiB
Go
133 lines
3.2 KiB
Go
// run
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// +build amd64
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// +build linux darwin
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"fmt"
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"syscall"
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)
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// Use global variables so the compiler
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// doesn't know that they are constants.
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var p = syscall.Getpagesize()
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var zero = 0
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var one = 1
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func main() {
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// Allocate 2 pages of memory.
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b, err := syscall.Mmap(-1, 0, 2*p, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANON|syscall.MAP_PRIVATE)
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if err != nil {
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panic(err)
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}
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// Mark the second page as faulting.
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err = syscall.Mprotect(b[p:], syscall.PROT_NONE)
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if err != nil {
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panic(err)
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}
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// Get a slice pointing to the last byte of the good page.
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x := b[p-one : p]
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test16(x)
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test16i(x, 0)
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test32(x)
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test32i(x, 0)
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test64(x)
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test64i(x, 0)
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}
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func test16(x []byte) uint16 {
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defer func() {
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r := recover()
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if r == nil {
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panic("no fault or bounds check failure happened")
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}
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s := fmt.Sprintf("%s", r)
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if s != "runtime error: index out of range [1] with length 1" {
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panic("bad panic: " + s)
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}
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}()
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// Try to read 2 bytes from x.
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return uint16(x[0]) | uint16(x[1])<<8
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// We expect to get an "index out of range" error from x[1].
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// If we promote the first load to a 2-byte load, it will segfault, which we don't want.
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}
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func test16i(x []byte, i int) uint16 {
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defer func() {
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r := recover()
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if r == nil {
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panic("no fault or bounds check failure happened")
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}
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s := fmt.Sprintf("%s", r)
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if s != "runtime error: index out of range [1] with length 1" {
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panic("bad panic: " + s)
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}
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}()
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return uint16(x[i]) | uint16(x[i+1])<<8
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}
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func test32(x []byte) uint32 {
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defer func() {
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r := recover()
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if r == nil {
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panic("no fault or bounds check failure happened")
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}
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s := fmt.Sprintf("%s", r)
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if s != "runtime error: index out of range [1] with length 1" {
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panic("bad panic: " + s)
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}
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}()
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return uint32(x[0]) | uint32(x[1])<<8 | uint32(x[2])<<16 | uint32(x[3])<<24
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}
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func test32i(x []byte, i int) uint32 {
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defer func() {
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r := recover()
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if r == nil {
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panic("no fault or bounds check failure happened")
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}
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s := fmt.Sprintf("%s", r)
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if s != "runtime error: index out of range [1] with length 1" {
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panic("bad panic: " + s)
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}
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}()
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return uint32(x[i]) | uint32(x[i+1])<<8 | uint32(x[i+2])<<16 | uint32(x[i+3])<<24
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}
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func test64(x []byte) uint64 {
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defer func() {
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r := recover()
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if r == nil {
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panic("no fault or bounds check failure happened")
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}
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s := fmt.Sprintf("%s", r)
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if s != "runtime error: index out of range [1] with length 1" {
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panic("bad panic: " + s)
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}
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}()
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return uint64(x[0]) | uint64(x[1])<<8 | uint64(x[2])<<16 | uint64(x[3])<<24 |
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uint64(x[4])<<32 | uint64(x[5])<<40 | uint64(x[6])<<48 | uint64(x[7])<<56
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}
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func test64i(x []byte, i int) uint64 {
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defer func() {
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r := recover()
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if r == nil {
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panic("no fault or bounds check failure happened")
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}
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s := fmt.Sprintf("%s", r)
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if s != "runtime error: index out of range [1] with length 1" {
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panic("bad panic: " + s)
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}
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}()
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return uint64(x[i+0]) | uint64(x[i+1])<<8 | uint64(x[i+2])<<16 | uint64(x[i+3])<<24 |
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uint64(x[i+4])<<32 | uint64(x[i+5])<<40 | uint64(x[i+6])<<48 | uint64(x[i+7])<<56
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}
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