test: stress test for stack objects

Allocate a long linked list on the stack. This tests both
lots of live stack objects, and lots of intra-stack pointers
to those objects.

Change-Id: I169e067416455737774851633b1e5367e10e1cf2
Reviewed-on: https://go-review.googlesource.com/c/135296
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

diff --git a/test/stackobj2.go b/test/stackobj2.go
new file mode 100644 (file)
index 0000000..a1abd9b
--- /dev/null
+++ b/test/stackobj2.go
@@ -0,0 +1,83 @@
+// 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 (
+       "fmt"
+       "runtime"
+)
+
+// linked list up the stack, to test lots of stack objects.
+
+type T struct {
+       // points to a heap object. Test will make sure it isn't freed.
+       data *int64
+       // next pointer for a linked list of stack objects
+       next *T
+       // duplicate of next, to stress test the pointer buffers
+       // used during stack tracing.
+       next2 *T
+}
+
+func main() {
+       makelist(nil, 10000)
+}
+
+func makelist(x *T, n int64) {
+       if n%2 != 0 {
+               panic("must be multiple of 2")
+       }
+       if n == 0 {
+               runtime.GC()
+               i := int64(1)
+               for ; x != nil; x, i = x.next, i+1 {
+                       // Make sure x.data hasn't been collected.
+                       if got := *x.data; got != i {
+                               panic(fmt.Sprintf("bad data want %d, got %d", i, got))
+                       }
+               }
+               return
+       }
+       // Put 2 objects in each frame, to test intra-frame pointers.
+       // Use both orderings to ensure the linked list isn't always in address order.
+       var a, b T
+       if n%3 == 0 {
+               a.data = newInt(n)
+               a.next = x
+               a.next2 = x
+               b.data = newInt(n - 1)
+               b.next = &a
+               b.next2 = &a
+               x = &b
+       } else {
+               b.data = newInt(n)
+               b.next = x
+               b.next2 = x
+               a.data = newInt(n - 1)
+               a.next = &b
+               a.next2 = &b
+               x = &a
+       }
+
+       makelist(x, n-2)
+}
+
+// big enough and pointer-y enough to not be tinyalloc'd
+type NotTiny struct {
+       n int64
+       p *byte
+}
+
+// newInt allocates n on the heap and returns a pointer to it.
+func newInt(n int64) *int64 {
+       h := &NotTiny{n: n}
+       p := &h.n
+       escape = p
+       return p
+}
+
+var escape *int64