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// 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 runtime_test
import (
"bytes"
"runtime"
"testing"
)
const (
typeScalar = 0
typePointer = 1
)
// TestGCInfo tests that various objects in heap, data and bss receive correct GC pointer type info.
func TestGCInfo(t *testing.T) {
verifyGCInfo(t, "bss Ptr", &bssPtr, infoPtr)
verifyGCInfo(t, "bss ScalarPtr", &bssScalarPtr, infoScalarPtr)
verifyGCInfo(t, "bss PtrScalar", &bssPtrScalar, infoPtrScalar)
verifyGCInfo(t, "bss BigStruct", &bssBigStruct, infoBigStruct())
verifyGCInfo(t, "bss string", &bssString, infoString)
verifyGCInfo(t, "bss slice", &bssSlice, infoSlice)
verifyGCInfo(t, "bss eface", &bssEface, infoEface)
verifyGCInfo(t, "bss iface", &bssIface, infoIface)
verifyGCInfo(t, "data Ptr", &dataPtr, infoPtr)
verifyGCInfo(t, "data ScalarPtr", &dataScalarPtr, infoScalarPtr)
verifyGCInfo(t, "data PtrScalar", &dataPtrScalar, infoPtrScalar)
verifyGCInfo(t, "data BigStruct", &dataBigStruct, infoBigStruct())
verifyGCInfo(t, "data string", &dataString, infoString)
verifyGCInfo(t, "data slice", &dataSlice, infoSlice)
verifyGCInfo(t, "data eface", &dataEface, infoEface)
verifyGCInfo(t, "data iface", &dataIface, infoIface)
{
var x Ptr
verifyGCInfo(t, "stack Ptr", &x, infoPtr)
runtime.KeepAlive(x)
}
{
var x ScalarPtr
verifyGCInfo(t, "stack ScalarPtr", &x, infoScalarPtr)
runtime.KeepAlive(x)
}
{
var x PtrScalar
verifyGCInfo(t, "stack PtrScalar", &x, infoPtrScalar)
runtime.KeepAlive(x)
}
{
var x BigStruct
verifyGCInfo(t, "stack BigStruct", &x, infoBigStruct())
runtime.KeepAlive(x)
}
{
var x string
verifyGCInfo(t, "stack string", &x, infoString)
runtime.KeepAlive(x)
}
{
var x []string
verifyGCInfo(t, "stack slice", &x, infoSlice)
runtime.KeepAlive(x)
}
{
var x any
verifyGCInfo(t, "stack eface", &x, infoEface)
runtime.KeepAlive(x)
}
{
var x Iface
verifyGCInfo(t, "stack iface", &x, infoIface)
runtime.KeepAlive(x)
}
for i := 0; i < 10; i++ {
verifyGCInfo(t, "heap Ptr", runtime.Escape(new(Ptr)), trimDead(infoPtr))
verifyGCInfo(t, "heap PtrSlice", runtime.Escape(&make([]*byte, 10)[0]), trimDead(infoPtr10))
verifyGCInfo(t, "heap ScalarPtr", runtime.Escape(new(ScalarPtr)), trimDead(infoScalarPtr))
verifyGCInfo(t, "heap ScalarPtrSlice", runtime.Escape(&make([]ScalarPtr, 4)[0]), trimDead(infoScalarPtr4))
verifyGCInfo(t, "heap PtrScalar", runtime.Escape(new(PtrScalar)), trimDead(infoPtrScalar))
verifyGCInfo(t, "heap BigStruct", runtime.Escape(new(BigStruct)), trimDead(infoBigStruct()))
verifyGCInfo(t, "heap string", runtime.Escape(new(string)), trimDead(infoString))
verifyGCInfo(t, "heap eface", runtime.Escape(new(any)), trimDead(infoEface))
verifyGCInfo(t, "heap iface", runtime.Escape(new(Iface)), trimDead(infoIface))
}
}
func verifyGCInfo(t *testing.T, name string, p any, mask0 []byte) {
mask := runtime.GCMask(p)
if bytes.HasPrefix(mask, mask0) {
// Just the prefix matching is OK.
//
// The Go runtime's pointer/scalar iterator generates pointers beyond
// the size of the type, up to the size of the size class. This space
// is safe for the GC to scan since it's zero, and GCBits checks to
// make sure that's true. But we need to handle the fact that the bitmap
// may be larger than we expect.
return
}
t.Errorf("bad GC program for %v:\nwant %+v\ngot %+v", name, mask0, mask)
}
func trimDead(mask []byte) []byte {
for len(mask) > 0 && mask[len(mask)-1] == typeScalar {
mask = mask[:len(mask)-1]
}
return mask
}
var infoPtr = []byte{typePointer}
type Ptr struct {
*byte
}
var infoPtr10 = []byte{typePointer, typePointer, typePointer, typePointer, typePointer, typePointer, typePointer, typePointer, typePointer, typePointer}
type ScalarPtr struct {
q int
w *int
e int
r *int
t int
y *int
}
var infoScalarPtr = []byte{typeScalar, typePointer, typeScalar, typePointer, typeScalar, typePointer}
var infoScalarPtr4 = append(append(append(append([]byte(nil), infoScalarPtr...), infoScalarPtr...), infoScalarPtr...), infoScalarPtr...)
type PtrScalar struct {
q *int
w int
e *int
r int
t *int
y int
}
var infoPtrScalar = []byte{typePointer, typeScalar, typePointer, typeScalar, typePointer, typeScalar}
type BigStruct struct {
q *int
w byte
e [17]byte
r []byte
t int
y uint16
u uint64
i string
}
func infoBigStruct() []byte {
switch runtime.GOARCH {
case "386", "arm", "mips", "mipsle":
return []byte{
typePointer, // q *int
typeScalar, typeScalar, typeScalar, typeScalar, typeScalar, // w byte; e [17]byte
typePointer, typeScalar, typeScalar, // r []byte
typeScalar, typeScalar, typeScalar, typeScalar, // t int; y uint16; u uint64
typePointer, typeScalar, // i string
}
case "arm64", "amd64", "loong64", "mips64", "mips64le", "ppc64", "ppc64le", "riscv64", "s390x", "wasm":
return []byte{
typePointer, // q *int
typeScalar, typeScalar, typeScalar, // w byte; e [17]byte
typePointer, typeScalar, typeScalar, // r []byte
typeScalar, typeScalar, typeScalar, // t int; y uint16; u uint64
typePointer, typeScalar, // i string
}
default:
panic("unknown arch")
}
}
type Iface interface {
f()
}
type IfaceImpl int
func (IfaceImpl) f() {
}
var (
// BSS
bssPtr Ptr
bssScalarPtr ScalarPtr
bssPtrScalar PtrScalar
bssBigStruct BigStruct
bssString string
bssSlice []string
bssEface any
bssIface Iface
// DATA
dataPtr = Ptr{new(byte)}
dataScalarPtr = ScalarPtr{q: 1}
dataPtrScalar = PtrScalar{w: 1}
dataBigStruct = BigStruct{w: 1}
dataString = "foo"
dataSlice = []string{"foo"}
dataEface any = 42
dataIface Iface = IfaceImpl(42)
infoString = []byte{typePointer, typeScalar}
infoSlice = []byte{typePointer, typeScalar, typeScalar}
infoEface = []byte{typeScalar, typePointer}
infoIface = []byte{typeScalar, typePointer}
)
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