time: In time.Unix, an underflow occurs when you put a large negative value in the seconds area

[myyrakle]

Go version

go version go1.21.4 linux/amd64

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

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/myyrakle/.cache/go-build'
GOENV='/home/myyrakle/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/myyrakle/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/myyrakle/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.21.4'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/myyrakle/Codes/Go/just_test/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build612091784=/tmp/go-build -gno-record-gcc-switches'

What did you do?

As follows, create a time object by entering the maximum and minimum values ​​of int64 and output it as a string.

package main

import (
	"fmt"
	"math"
	"time"
)

func main() {
	fmt.Println(time.Unix(math.MaxInt64, 0)) // 292277026596-12-05 00:30:07 +0900 KST
	fmt.Println(time.Unix(math.MinInt64, 0)) // 292277026596-12-04 23:58:00 +0827 LMT
}

What did you expect to see?

I expected max to be a very large time value, and min to be a negative time value similar to max.

What did you see instead?

In the case of the maximum value, very large time values ​​are output as positive numbers, as intended.

However, for the minimum value, a positive number is output, even though it should be a negative value.

When I tested it myself, the minimum value that was actually output as a negative number was time.Unix(math.MinInt64+8139423736, 0).
An underflow occurs starting from time.Unix(math.MinInt64+8139423735, 0).

However, it doesn't seem to be specified in the document.

Is this behavior by design? Or is this a bug or undefined behavior?

[mauri870]

kindly cc @rsc, per https://dev.golang.org/owners

[AlexanderYastrebov]

Related issues #56909 and #63844