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time: Time.MarshalBinary loses monotonic component #20255

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ggaaooppeenngg opened this issue May 5, 2017 · 1 comment

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commented May 5, 2017

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version devel +8db4d02 Fri Apr 28 07:27:25 2017 +0000 darwin/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/gaopeng/Workplace/GOPATH"
GORACE=""
GOROOT="/Users/gaopeng/Workplace/go"
GOTOOLDIR="/Users/gaopeng/Workplace/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/mf/smd0sz4s6b13k6fg88_nc1240000gn/T/go-build220820873=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

By adding patch in src/time/time.go

+func (t Time) GetWallAndExt() (uint64, int64) {
+       return t.wall, t.ext
+}
+
+func (t *Time) SetWallAndExt(wall uint64, ext int64) {
+       t.wall = wall
+       t.ext = ext
+}

I run this program

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
	"time"
)

// 13707589861482070995 464861
// 610436051 63629562089
func main() {
	var buf bytes.Buffer
	t := time.Now()
	t.SetWallAndExt(13707589861482070995, 464861)
	fmt.Println(t)
	fmt.Println(gob.NewEncoder(&buf).Encode(t))
	var t1 time.Time
	fmt.Println(gob.NewDecoder(&buf).Decode(&t1))

	w, e := t.GetWallAndExt()
	fmt.Printf("0x%b 0x%b\n", w, e)
	fmt.Println(t)

	w, e = t1.GetWallAndExt()
	fmt.Printf("0x%b 0x%b\n", w, e)
	fmt.Println(t1)
}

What did you expect to see?

0x1011111000111011001001000101101001100100011000101000001111010011 0x1110001011111011101
2017-05-05 14:21:29.610436051 +0800 CST m=+0.000464861
0x100100011000101000001111010011 0x111011010000100111100001000011101001
2017-05-05 14:21:29.610436051 +0800 CST m=+0.000464861

What did you see instead?

0x1011111000111011001001000101101001100100011000101000001111010011 0x1110001011111011101
2017-05-05 14:21:29.610436051 +0800 CST m=+0.000464861
0x100100011000101000001111010011 0x111011010000100111100001000011101001
2017-05-05 14:21:29.610436051 +0800 CST

BTW, I found related issue #12914 and #19502, and I propose to rm final field m=±<value> in Time.String(), since we should follow the way wall clock is used to show time, and monotonic clock is used to comparison.

@ggaaooppeenngg ggaaooppeenngg changed the title gob encode encode monotonic time to wall time time: BinaryMarshal encodes monotonic time to wall time May 5, 2017

@bradfitz bradfitz changed the title time: BinaryMarshal encodes monotonic time to wall time time: BinaryMarshal loses monotonic component of Time May 5, 2017

@bradfitz bradfitz added this to the Go1.9 milestone May 5, 2017

@bradfitz bradfitz changed the title time: BinaryMarshal loses monotonic component of Time time: Time.MarshalBinary loses monotonic component May 5, 2017

@bradfitz

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commented May 5, 2017

Actually, this is intentional. The monotonic component of a Time value is only meaningful within a current process for comparison with other such Times. It should not be serialized and read later.

@bradfitz bradfitz closed this May 5, 2017

@golang golang locked and limited conversation to collaborators May 5, 2018

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