encoding/gob: race on idToType #23328
Description
On current master, this program sometimes fails when using the race detector:
package main
import (
"bytes"
"encoding/gob"
"fmt"
"sync"
)
type S0 struct {
I int
}
type S1 struct {
I int
}
type S2 struct {
I int
}
type S3 struct {
I int
}
type S4 struct {
I int
}
type S5 struct {
I int
}
type S6 struct {
I int
}
type S7 struct {
I int
}
type S8 struct {
I int
}
type S9 struct {
I int
}
func main() {
c := make(chan bool)
var wg sync.WaitGroup
for i := 0; i < 10; i++ {
wg.Add(1)
go func(i int) {
defer wg.Done()
var buf bytes.Buffer
var x interface{}
switch i {
case 0:
x = &S0{0}
case 1:
x = &S1{1}
case 2:
x = &S2{2}
case 3:
x = &S3{3}
case 4:
x = &S4{4}
case 5:
x = &S5{5}
case 6:
x = &S6{6}
case 7:
x = &S7{7}
case 8:
x = &S8{8}
case 9:
x = &S9{9}
default:
panic(i)
}
enc := gob.NewEncoder(&buf)
dec := gob.NewDecoder(&buf)
<-c
if err := enc.Encode(x); err != nil {
fmt.Println(err)
}
if err := enc.Encode(x); err != nil {
fmt.Println(err)
}
m := make(map[string]string)
// This call to Decode is expected to fail.
dec.Decode(&m)
}(i)
}
close(c)
wg.Wait()
}Sample failure:
==================
WARNING: DATA RACE
Write at 0x00c4200961e0 by goroutine 7:
runtime.mapassign_fast32()
/home/iant/go/src/runtime/hashmap_fast.go:350 +0x0
encoding/gob.setTypeId()
/home/iant/go/src/encoding/gob/type.go:186 +0xf8
encoding/gob.newStructType()
/home/iant/go/src/encoding/gob/type.go:429 +0xb6
encoding/gob.newTypeObject()
/home/iant/go/src/encoding/gob/type.go:522 +0xd36
encoding/gob.getType()
/home/iant/go/src/encoding/gob/type.go:598 +0x112
encoding/gob.getBaseType()
/home/iant/go/src/encoding/gob/type.go:585 +0x94
encoding/gob.buildTypeInfo()
/home/iant/go/src/encoding/gob/type.go:715 +0x106
encoding/gob.getTypeInfo()
/home/iant/go/src/encoding/gob/type.go:702 +0xed
encoding/gob.(*Encoder).sendActualType()
/home/iant/go/src/encoding/gob/encoder.go:96 +0xcb
encoding/gob.(*Encoder).sendType()
/home/iant/go/src/encoding/gob/encoder.go:168 +0x116
encoding/gob.(*Encoder).sendTypeDescriptor()
/home/iant/go/src/encoding/gob/encoder.go:190 +0x166
encoding/gob.(*Encoder).EncodeValue()
/home/iant/go/src/encoding/gob/encoder.go:243 +0x52c
encoding/gob.(*Encoder).Encode()
/home/iant/go/src/encoding/gob/encoder.go:175 +0x72
main.main.func1()
/home/iant/foo8.go:86 +0x1d8
Previous read at 0x00c4200961e0 by goroutine 13:
runtime.mapaccess1_fast32()
/home/iant/go/src/runtime/hashmap_fast.go:12 +0x0
encoding/gob.(*Decoder).typeString()
/home/iant/go/src/encoding/gob/decode.go:1041 +0x76
encoding/gob.(*Decoder).compileSingle()
/home/iant/go/src/encoding/gob/decode.go:1056 +0x563
encoding/gob.(*Decoder).compileDec()
/home/iant/go/src/encoding/gob/decode.go:1088 +0x132
encoding/gob.(*Decoder).getDecEnginePtr()
/home/iant/go/src/encoding/gob/decode.go:1145 +0x23b
encoding/gob.(*Decoder).decodeValue()
/home/iant/go/src/encoding/gob/decode.go:1190 +0x10b
encoding/gob.(*Decoder).DecodeValue()
/home/iant/go/src/encoding/gob/decoder.go:212 +0x1cb
encoding/gob.(*Decoder).Decode()
/home/iant/go/src/encoding/gob/decoder.go:187 +0x1c9
main.main.func1()
/home/iant/foo8.go:94 +0x371
Goroutine 7 (running) created at:
main.main()
/home/iant/foo8.go:55 +0xd9
Goroutine 13 (finished) created at:
main.main()
/home/iant/foo8.go:55 +0xd9
==================
Found 1 data race(s)
exit status 66
This is not a new failure but it's probably simple to fix.