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// run
// Copyright 2011 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.
// Test that the implementation catches nil ptr indirection
// in a large address space.
package main
import "unsafe"
// Having a big address space means that indexing
// at a 256 MB offset from a nil pointer might not
// cause a memory access fault. This test checks
// that Go is doing the correct explicit checks to catch
// these nil pointer accesses, not just relying on the hardware.
var dummy [256 << 20]byte // give us a big address space
func main() {
// the test only tests what we intend to test
// if dummy starts in the first 256 MB of memory.
// otherwise there might not be anything mapped
// at the address that might be accidentally
// dereferenced below.
if uintptr(unsafe.Pointer(&dummy)) > 256<<20 {
panic("dummy too far out")
}
shouldPanic(p1)
shouldPanic(p2)
shouldPanic(p3)
shouldPanic(p4)
shouldPanic(p5)
shouldPanic(p6)
shouldPanic(p7)
shouldPanic(p8)
shouldPanic(p9)
shouldPanic(p10)
shouldPanic(p11)
shouldPanic(p12)
}
func shouldPanic(f func()) {
defer func() {
if recover() == nil {
panic("memory reference did not panic")
}
}()
f()
}
func p1() {
// Array index.
var p *[1 << 30]byte = nil
println(p[256<<20]) // very likely to be inside dummy, but should panic
}
var xb byte
func p2() {
var p *[1 << 30]byte = nil
xb = 123
// Array index.
println(p[uintptr(unsafe.Pointer(&xb))]) // should panic
}
func p3() {
// Array to slice.
var p *[1 << 30]byte = nil
var x []byte = p[0:] // should panic
_ = x
}
var q *[1 << 30]byte
func p4() {
// Array to slice.
var x []byte
var y = &x
*y = q[0:] // should crash (uses arraytoslice runtime routine)
}
func fb([]byte) {
panic("unreachable")
}
func p5() {
// Array to slice.
var p *[1 << 30]byte = nil
fb(p[0:]) // should crash
}
func p6() {
// Array to slice.
var p *[1 << 30]byte = nil
var _ []byte = p[10 : len(p)-10] // should crash
}
type T struct {
x [256 << 20]byte
i int
}
func f() *T {
return nil
}
var y *T
var x = &y
func p7() {
// Struct field access with large offset.
println(f().i) // should crash
}
func p8() {
// Struct field access with large offset.
println((*x).i) // should crash
}
func p9() {
// Struct field access with large offset.
var t *T
println(&t.i) // should crash
}
func p10() {
// Struct field access with large offset.
var t *T
println(t.i) // should crash
}
type T1 struct {
T
}
type T2 struct {
*T1
}
func p11() {
t := &T2{}
p := &t.i
println(*p)
}
// ADDR(DOT(IND(p))) needs a check also
func p12() {
var p *T = nil
println(*(&((*p).i)))
}
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