1 files changed, 31 insertions, 0 deletions
diff --git a/test/nilptr/arrayindex1.go b/test/nilptr/arrayindex1.go
new file mode 100644
index 000000000..64f46e14d
--- /dev/null
+++ b/test/nilptr/arrayindex1.go
@@ -0,0 +1,31 @@
+// $G $D/$F.go && $L $F.$A &&
+//	((! sh -c ./$A.out) >/dev/null 2>&1 || 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 dummy [512<<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")
+	}
+
+	// The problem here 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.
+	var p *[1<<30]byte = nil
+	println(p[256<<20])	// very likely to be inside dummy, but should crash
+}