Object with time.Time field doesn't equal itself after gob encode/decode (go 1.9+)

[vovka667]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.9.2 linux/amd64

Does this issue reproduce with the latest release?

Yes. It reproduces with Go version 1.9 and above.

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/vovka/pr/go"
GORACE=""
GOROOT="/home/vovka/.golang/stable"
GOTOOLDIR="/home/vovka/.golang/stable/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build079377208=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
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?

https://play.golang.org/p/Bz82uni81C

What did you expect to see?

something like this:

$ go version
go version go1.8.5 linux/amd64
$ go run main.go
gob:
        Before: &main.someObjectWithTime{Time:time.Time{sec:63644866279, nsec:191418226, loc:(*time.Location)(0x572660)}}
        After:  &main.someObjectWithTime{Time:time.Time{sec:63644866279, nsec:191418226, loc:(*time.Location)(0x572660)}}
        reflect.DeepEqual: true

What did you see instead?

$ go version
go version go1.9.2 linux/amd64
$ go run main.go
gob:
        Before: &main.someObjectWithTime{Time:time.Time{wall:0xbe7585dacdb772e0, ext:1437579, loc:(*time.Location)(0x593820)}}
        After:  &main.someObjectWithTime{Time:time.Time{wall:0xdb772e0, ext:63644866283, loc:(*time.Location)(0x593820)}}
        reflect.DeepEqual: false

[nussjustin]

That's the expected behaviour, since encoding a time.Time strips the monotonic time part. See the part about comparisons in time.Time's documentation:

Note that the Go == operator compares not just the time instant but also the Location and the monotonic clock reading. Therefore, Time values should not be used as map or database keys without first guaranteeing that the identical Location has been set for all values, which can be achieved through use of the UTC or Local method, and that the monotonic clock reading has been stripped by setting t = t.Round(0). In general, prefer t.Equal(u) to t == u, since t.Equal uses the most accurate comparison available and correctly handles the case when only one of its arguments has a monotonic clock reading.

If you want to compare two time.Time instances you should use Time.Equal.

[ghost]

Rel #22251

[ALTree]

Yes, as explained above this is expected.

Closing as a dup of #22251 (and others).