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bug: pointer arithmetic involving large offsets

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needs to dereference the base pointer to make
sure it catches nil.

R=r,ken
DELTA=21  (21 added, 0 deleted, 0 changed)
OCL=30083
CL=30101
This commit is contained in:
Russ Cox 2009-06-09 09:45:30 -07:00
parent b05c6fe23a
commit bf5c0c957c
1 changed files with 25 additions and 0 deletions
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25
test/bugs/bug162.go Normal file
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// $G $D/$F.go && $L $F.$A && (! ./$A.out || echo BUG: should fail)
// Copyright 2009 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 "unsafe"
var x byte
func main() {
var p *[1<<30]byte = nil;
x = 123;
// The problem here is not the use of unsafe:
// it is that indexing into p[] with a large
// enough index jumps out of the unmapped section
// at the beginning of memory and into valid memory.
// Pointer offsets and array indices, if they are
// very large, need to dereference the base pointer
// to trigger a trap.
println(p[uintptr(unsafe.Pointer(&x))]);
}