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go/test/fixedbugs/issue24187.go
Josh Bleecher Snyder aa9c1a8f80 runtime: fix amd64p32 indexbytes in presence of overflow
When the slice/string length is very large,
probably artifically large as in CL 97523,
adding BX (length) to R11 (pointer) overflows.
As a result, checking DI < R11 yields the wrong result.
Since they will be equal when the loop is done,
just check DI != R11 instead.
Yes, the pointer itself could overflow, but if that happens,
something else has gone pretty wrong; not our concern here.

Fixes #24187

Change-Id: I2f60fc6ccae739345d01bc80528560726ad4f8c6
Reviewed-on: https://go-review.googlesource.com/97802
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
2018-03-01 16:53:33 +00:00

34 lines
602 B
Go

// +build amd64p32
// 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.
package main
import (
"bytes"
"fmt"
"unsafe"
)
func main() {
b := make([]byte, 128)
for i := range b {
b[i] = 1
}
if bytes.IndexByte(b, 0) != -1 {
panic("found 0")
}
for i := range b {
b[i] = 0
c := b
*(*int)(unsafe.Pointer(uintptr(unsafe.Pointer(&c)) + unsafe.Sizeof(uintptr(0)))) = 1<<31 - 1
if bytes.IndexByte(c, 0) != i {
panic(fmt.Sprintf("missing 0 at %d\n", i))
}
b[i] = 1
}
}