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fmt: Scan extra input when switching languages #45354

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Dezmmond opened this issue Apr 2, 2021 · 4 comments
Closed

fmt: Scan extra input when switching languages #45354

Dezmmond opened this issue Apr 2, 2021 · 4 comments
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FrozenDueToAge WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided.

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@Dezmmond
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Dezmmond commented Apr 2, 2021 •
edited

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

$ go version
go version go1.16.3 linux/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/root/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/root/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.16.3"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2160470449=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I wrote and tested this program:

My program Output
package main

import . "fmt"


func main() {

var (

name string

age int

)

Print("Введите имя: ")

Scanln(&name)

Print("Введите возраст: ")

Scanln(&age)


Println(name, age)



}

Algorithm:

  1. Started the program.
  2. In the name input field, I entered the text first in Cyrillic (text: Vuy), then completely erased it, switched the layout from American to Russian with the keyboard shortcut "Alt+Shift" and wrote in Latin (text: Dezm), then pressed the "Enter"button.
  3. In the age input field, enter the numbers (88), and then click the "Enter" button.

What did you expect to see?

In stdout i expected to see: Dezm 88

What did you see instead?

But i see instead: ВуDezm 88
@seankhliao seankhliao changed the title Error in the fmt.Scan() and fmt.Scanln() functions fmt: Scan extra input when switching languages Apr 2, 2021
@seankhliao
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Can you try it with the following and post the output?
Though I think this is more likely an issue with the terminal and/or input method than with Go.

(cribbed from #23562 (comment))

package main

import (
	"fmt"
	"os"
)

type myReader struct{}

func (r myReader) Read(p []byte) (n int, err error) {
	n, err = os.Stdin.Read(p)
	fmt.Fprintf(os.Stderr, "DEBUG: %q %v\n", p[:n], err)
	return n, err
}

func main() {
	var (
		name string
		age  int

		input = &myReader{}
	)

	fmt.Print("Введите имя: ")
	fmt.Fscanln(input, &name)

	fmt.Print("Введите возраст: ")
	fmt.Fscanln(input, &age)

	fmt.Println(name, age)
}

@seankhliao seankhliao added the WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. label Apr 2, 2021
@ghost
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ghost commented Apr 3, 2021

I can't reproduce this in Konsole, so I guess the culprit is indeed the issue author's terminal emulator or input method.

@Dezmmond
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Dezmmond commented Apr 5, 2021

This is my output:

Введите имя: Dezm
DEBUG: "\xd0"
DEBUG: "\x92"
DEBUG: "\xd1"
DEBUG: "\x83"
DEBUG: "D"
DEBUG: "e"
DEBUG: "z"
DEBUG: "m"
DEBUG: "\n"
Введите возраст: 88
DEBUG: "8"
DEBUG: "8"
DEBUG: "\n"
ВуDezm 88

@seankhliao
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So fmt is correctly processing what comes in on STDIN, you'll have to look elsewhere to find why the extra characters are passed to the program.

Closing as this is not a bug with Go

@golang golang locked and limited conversation to collaborators Apr 5, 2022
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@gopherbot @seankhliao @Dezmmond