"checkptr: pointer arithmetic result points to invalid allocation" caused by #81

[aaron42net]

Using segmentio/encoding v0.2.16 on both MacOS and Linux with Go 1.16.2, I get fatal error: checkptr: pointer arithmetic result points to invalid allocation from Go's race detector pointing a finger at ascii/valid_print.go:31 with certain input to json.Marshal(), suggesting it is related to #81.

Here's simplified test code to trigger it:

package main

import (
	"testing"

	"github.com/segmentio/encoding/json"
)

type Foo struct {
	Source struct {
		Table string
	}
}

func TestUnmarshal(t *testing.T) {
	input := []byte(`{"source": {"table": "1234567"}}`)
	r := &Foo{}
	json.Unmarshal(input, r)
}

Run:

go mod init segtest
go mod tidy
go test -v -race -trimpath ./...

And you should see:

fatal error: checkptr: pointer arithmetic result points to invalid allocation

goroutine 19 [running]:
runtime.throw(0x12669e8, 0x40)
	runtime/panic.go:1117 +0x72 fp=0xc000042b28 sp=0xc000042af8 pc=0x1078352
runtime.checkptrArithmetic(0xc00012a060, 0xc000042bc8, 0x1, 0x1)
	runtime/checkptr.go:43 +0xbe fp=0xc000042b58 sp=0xc000042b28 pc=0x1047b7e
github.com/segmentio/encoding/ascii.ValidPrintString(0xc00012a040, 0x20, 0x1)
	github.com/segmentio/encoding@v0.2.16/ascii/valid_print.go:31 +0x4e5 fp=0xc000042be0 sp=0xc000042b58 pc=0x11d2725
github.com/segmentio/encoding/ascii.ValidPrint(...)
	github.com/segmentio/encoding@v0.2.16/ascii/valid_print.go:8
github.com/segmentio/encoding/json.internalParseFlags(0xc00012a040, 0x20, 0x20, 0xc000121380)
	github.com/segmentio/encoding@v0.2.16/json/parse.go:33 +0xcb fp=0xc000042c68 sp=0xc000042be0 pc=0x120420b
github.com/segmentio/encoding/json.Parse(0xc00012a040, 0x20, 0x20, 0x1223620, 0xc00011a520, 0x0, 0x10, 0xc000030640, 0xc00011a520, 0x138f720, ...)
	github.com/segmentio/encoding@v0.2.16/json/json.go:303 +0x114 fp=0xc000042dd0 sp=0xc000042c68 pc=0x1203a94
github.com/segmentio/encoding/json.Unmarshal(0xc00012a040, 0x20, 0x20, 0x1223620, 0xc00011a520, 0x0, 0x0)
	github.com/segmentio/encoding@v0.2.16/json/json.go:285 +0x93 fp=0xc000042e78 sp=0xc000042dd0 pc=0x1203833
segtest.TestUnmarshal(0xc000102900)
	segtest/main_test.go:18 +0x108 fp=0xc000042ed0 sp=0xc000042e78 pc=0x1213b68

If you can't reproduce, I'd be happy to provide more detail.

[achille-roussel]

Thanks for reporting @aaron42net, I'm looking into this.

[achille-roussel]

The fix was released in v0.2.17