1// run
2
3// Copyright 2018 The Go Authors. All rights reserved.
4// Use of this source code is governed by a BSD-style
5// license that can be found in the LICENSE file.
6
7// Verify that we don't consider a Go'd function's
8// arguments as pointers when they aren't.
9
10package main
11
12import (
13	"unsafe"
14)
15
16var badPtr uintptr
17
18var sink []byte
19
20func init() {
21	// Allocate large enough to use largeAlloc.
22	b := make([]byte, 1<<16-1)
23	sink = b // force heap allocation
24	//  Any space between the object and the end of page is invalid to point to.
25	badPtr = uintptr(unsafe.Pointer(&b[len(b)-1])) + 1
26}
27
28var throttle = make(chan struct{}, 10)
29
30// There are 2 arg bitmaps for this function, each with 2 bits.
31// In the first, p and q are both live, so that bitmap is 11.
32// In the second, only p is live, so that bitmap is 10.
33// Bitmaps are byte aligned, so if the first bitmap is interpreted as
34// extending across the entire argument area, we incorrectly concatenate
35// the bitmaps and end up using 110000001. That bad bitmap causes a6
36// to be considered a pointer.
37func noPointerArgs(p, q *byte, a0, a1, a2, a3, a4, a5, a6 uintptr) {
38	sink = make([]byte, 4096)
39	sinkptr = q
40	<-throttle
41	sinkptr = p
42}
43
44var sinkptr *byte
45
46func main() {
47	const N = 1000
48	for i := 0; i < N; i++ {
49		throttle <- struct{}{}
50		go noPointerArgs(nil, nil, badPtr, badPtr, badPtr, badPtr, badPtr, badPtr, badPtr)
51		sink = make([]byte, 4096)
52	}
53}
54