diff options
author | Russ Cox <rsc@golang.org> | 2014-08-25 14:38:19 -0400 |
---|---|---|
committer | Russ Cox <rsc@golang.org> | 2014-08-25 14:38:19 -0400 |
commit | 588ffed86c777b6270c341fffadbbfb82f2c6a9c (patch) | |
tree | 4e5302f4267cc27b1bc1e04c5c4469f577f0ec0d /test/slicecap.go | |
parent | e4b65ea6a0b2755b284d20e1822ea2db8df9a7e6 (diff) | |
download | go-588ffed86c777b6270c341fffadbbfb82f2c6a9c.tar.gz |
cmd/gc, runtime: treat slices and strings like pointers in garbage collection
Before, a slice with cap=0 or a string with len=0 might have its
base pointer pointing beyond the actual slice/string data into
the next block. The collector had to ignore slices and strings with
cap=0 in order to avoid misinterpreting the base pointer.
Now, a slice with cap=0 or a string with len=0 still has a base
pointer pointing into the actual slice/string data, no matter what.
The collector can now always scan the pointer, which means
strings and slices are no longer special.
Fixes issue 8404.
LGTM=khr, josharian
R=josharian, khr, dvyukov
CC=golang-codereviews
https://codereview.appspot.com/112570044
Diffstat (limited to 'test/slicecap.go')
-rw-r--r-- | test/slicecap.go | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/test/slicecap.go b/test/slicecap.go new file mode 100644 index 000000000..dceb7e2cc --- /dev/null +++ b/test/slicecap.go @@ -0,0 +1,90 @@ +// run + +// Copyright 2014 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 ( + hello = "hello" + bytes = []byte{1, 2, 3, 4, 5} + ints = []int32{1, 2, 3, 4, 5} + + five = 5 + + ok = true +) + +func notOK() { + if ok { + println("BUG:") + ok = false + } +} + +func checkString(desc, s string) { + p1 := *(*uintptr)(unsafe.Pointer(&s)) + p2 := *(*uintptr)(unsafe.Pointer(&hello)) + if p1-p2 >= 5 { + notOK() + println("string", desc, "has invalid base") + } +} + +func checkBytes(desc string, s []byte) { + p1 := *(*uintptr)(unsafe.Pointer(&s)) + p2 := *(*uintptr)(unsafe.Pointer(&bytes)) + if p1-p2 >= 5 { + println("byte slice", desc, "has invalid base") + } +} + +func checkInts(desc string, s []int32) { + p1 := *(*uintptr)(unsafe.Pointer(&s)) + p2 := *(*uintptr)(unsafe.Pointer(&ints)) + if p1-p2 >= 5*4 { + println("int slice", desc, "has invalid base") + } +} + +func main() { + { + x := hello + checkString("x", x) + checkString("x[5:]", x[5:]) + checkString("x[five:]", x[five:]) + checkString("x[5:five]", x[5:five]) + checkString("x[five:5]", x[five:5]) + checkString("x[five:five]", x[five:five]) + checkString("x[1:][2:][2:]", x[1:][2:][2:]) + y := x[4:] + checkString("y[1:]", y[1:]) + } + { + x := bytes + checkBytes("x", x) + checkBytes("x[5:]", x[5:]) + checkBytes("x[five:]", x[five:]) + checkBytes("x[5:five]", x[5:five]) + checkBytes("x[five:5]", x[five:5]) + checkBytes("x[five:five]", x[five:five]) + checkBytes("x[1:][2:][2:]", x[1:][2:][2:]) + y := x[4:] + checkBytes("y[1:]", y[1:]) + } + { + x := ints + checkInts("x", x) + checkInts("x[5:]", x[5:]) + checkInts("x[five:]", x[five:]) + checkInts("x[5:five]", x[5:five]) + checkInts("x[five:5]", x[five:5]) + checkInts("x[five:five]", x[five:five]) + checkInts("x[1:][2:][2:]", x[1:][2:][2:]) + y := x[4:] + checkInts("y[1:]", y[1:]) + } +} |