cmd/go: Program exits abruptly with the 語 character #50105

gkamathe · 2021-12-11T15:59:49Z

I was playing around with a simple program to see how bytes/runes work

$ cat main.go 
package main

import (
	"fmt"
)

func main() {
	s := "hello"
	for i := 0; i < len(s); i++ {
		c := s[i]
		fmt.Printf("index : %d has char : %c which is hex : 0x%x\n", i, c, c)
	}

	for i, rchar := range s {
		fmt.Printf("Rune at byte position : %d is : %#U\n", i, rchar)
	}
}
$

Running it gave the expected results

$ go run main.go 
index : 0 has char : h which is hex : 0x68
index : 1 has char : e which is hex : 0x65
index : 2 has char : l which is hex : 0x6c
index : 3 has char : l which is hex : 0x6c
index : 4 has char : o which is hex : 0x6f
Rune at byte position : 0 is : U+0068 'h'
Rune at byte position : 1 is : U+0065 'e'
Rune at byte position : 2 is : U+006C 'l'
Rune at byte position : 3 is : U+006C 'l'
Rune at byte position : 4 is : U+006F 'o'
$

Next I thought of using words from a different language for s

$ cat main.go 
package main

import (
	"fmt"
)

func main() {
	// s := "hello"
	s := "日本語"
	for i := 0; i < len(s); i++ {
		c := s[i]
		fmt.Printf("index : %d has char : %c which is hex : 0x%x\n", i, c, c)
	}

	for i, rchar := range s {
		fmt.Printf("Rune at byte position : %d is : %#U\n", i, rchar)
	}
}
$

Did you notice what happened ? The second for loop never ran ?
What ?

$ go run main.go 
index : 0 has char : æ which is hex : 0xe6
index : 1 has char :  which is hex : 0x97
index : 2 has char : ¥ which is hex : 0xa5
index : 3 has char : æ which is hex : 0xe6
index : 4 has char :  which is hex : 0x9c
index : 5 has char : ¬ which is hex : 0xac
index : 6 has char : è which is hex : 0xe8
index : 7 has char : ª which is hex : 0xaa
index : 8 has char : $

Ok, next I tried to insert a fmt.Println to print random "======"

$ cat main.go 
package main

import (
	"fmt"
)

func main() {
	// s := "hello"
	s := "日本語"
	for i := 0; i < len(s); i++ {
		c := s[i]
		fmt.Printf("index : %d has char : %c which is hex : 0x%x\n", i, c, c)
	}

	fmt.Println("========================")
	for i, rchar := range s {
		fmt.Printf("Rune at byte position : %d is : %#U\n", i, rchar)
	}
}
$

Same behavior ? So the problem lies in the first for loop

$ go run main.go 
index : 0 has char : æ which is hex : 0xe6
index : 1 has char :  which is hex : 0x97
index : 2 has char : ¥ which is hex : 0xa5
index : 3 has char : æ which is hex : 0xe6
index : 4 has char :  which is hex : 0x9c
index : 5 has char : ¬ which is hex : 0xac
index : 6 has char : è which is hex : 0xe8
index : 7 has char : ª which is hex : 0xaa
index : 8 has char : $

To narrow down the issue, I chose a different set of characters from the same language

$ cat main.go 
package main

import (
	"fmt"
)

func main() {
	// s := "日本語"
	s := "こんにちは"
	for i := 0; i < len(s); i++ {
		c := s[i]
		fmt.Printf("index : %d has char : %c which is hex : 0x%x\n", i, c, c)
	}

	for i, rchar := range s {
		fmt.Printf("Rune at byte position : %d is : %#U\n", i, rchar)
	}
}
$

This time it ran fine, second for loop executed. Hmmm

$ go run main.go 
index : 0 has char : ã which is hex : 0xe3
index : 1 has char :  which is hex : 0x81
index : 2 has char :  which is hex : 0x93
index : 3 has char : ã which is hex : 0xe3
index : 4 has char :  which is hex : 0x82
index : 5 has char :  which is hex : 0x93
index : 6 has char : ã which is hex : 0xe3
index : 7 has char :  which is hex : 0x81
index : 8 has char : « which is hex : 0xab
index : 9 has char : ã which is hex : 0xe3
index : 10 has char :  which is hex : 0x81
index : 11 has char : ¡ which is hex : 0xa1
index : 12 has char : ã which is hex : 0xe3
index : 13 has char :  which is hex : 0x81
index : 14 has char : ¯ which is hex : 0xaf
Rune at byte position : 0 is : U+3053 'こ'
Rune at byte position : 3 is : U+3093 'ん'
Rune at byte position : 6 is : U+306B 'に'
Rune at byte position : 9 is : U+3061 'ち'
Rune at byte position : 12 is : U+306F 'は'
$

I focused on the problematic characters picking one at a time

s := "日"

Program worked fine for this character

$ go run main.go 
index : 0 has char : æ which is hex : 0xe6
index : 1 has char :  which is hex : 0x97
index : 2 has char : ¥ which is hex : 0xa5
Rune at byte position : 0 is : U+65E5 '日'
$

Moved to the next character

s := "本"

Again worked fine

$ go run main.go 
index : 0 has char : æ which is hex : 0xe6
index : 1 has char :  which is hex : 0x9c
index : 2 has char : ¬ which is hex : 0xac
Rune at byte position : 0 is : U+672C '本'
$

Which leaves the final character

s := "語"

And as expected the program seems to exit ? Second for loop never printed

$ go run main.go 
index : 0 has char : è which is hex : 0xe8
index : 1 has char : ª which is hex : 0xaa
index : 2 has char : $

I tried running the program on the Go playground and it seemed to work fine there
I am using the following version of Go on a Fedora distribution

$ go version
go version go1.16.8 linux/amd64
$

If you notice where the exit happens

index : 2 has char : $

It seems its coming from this line, so is %c or %x the problem here ?
Anybody else able to reproduce it on the exact same version ?

fmt.Printf("index : %d has char : %c which is hex : 0x%x\n", i, c, c)

I casually tried to reproduce the issue on various different online Go playgrounds (non-Google) too, by adding the line below to programs

fmt.Println(runtime.Version())

I am also seeing the issue on below version for an online playground here (https://www.onlinegdb.com/online_go_compiler)

go1.12.7

The text was updated successfully, but these errors were encountered:

seankhliao · 2021-12-11T16:19:47Z

The program doesn't terminate, just your terminal can't display what it considers to be invalid output.

Closing as not a bug in go

zyxkad · 2021-12-11T16:22:02Z

Hi, can you show your platform?
I try to run this program on my computer

$ go version
go version go1.17.2 darwin/amd64

I couldn't find any problem

gkamathe · 2021-12-11T16:27:47Z

@seankhliao In that case shouldn't the 2nd for loop at least run and print Output beginning with "Rune at byte position..." ? even if it doesn't print the actual characters ?

@zyxkad I am running Fedora on my laptop, Already gave the Go version above, Could you try this Golang online compiler here https://www.onlinegdb.com/online_go_compiler and try out the below program ? You can see that 2nd loop doesn't show all the characters either

package main

import (
	"fmt"
	"runtime"
)

func main() {
	s := "日本語"
	for i := 0; i < len(s); i++ {
		c := s[i]
		fmt.Printf("index : %d has char : %c which is hex : 0x%x\n", i, c, c)
	}

	for i, rchar := range s {
		fmt.Printf("Rune at byte position : %d is : %#U\n", i, rchar)
	}

    fmt.Println(runtime.Version())
}

Here is the output I see on the above Golang online playground

index : 0 has char : æ which is hex : 0xe6
index : 1 has char :  which is hex : 0x97
index : 2 has char : ¥ which is hex : 0xa5
index : 3 has char : æ which is hex : 0xe6
index : 4 has char :  which is hex : 0x9c
index : 5 has char : ¬ which is hex : 0xac
index : 6 has char : è which is hex : 0xe8
index : 7 has char : ª which is hex : 0xaa
index : 8 has char : '
Rune at byte position : 3 is : U+672C '本'
Rune at byte position : 6 is : U+8A9E '語'
go1.12.7

ianlancetaylor · 2021-12-11T16:57:02Z

For questions about how Go works and how to use it, please use a forum, not the issue tracker. See https://golang.org/wiki/Questions. Thanks.

seankhliao closed this as completed Dec 11, 2021

golang locked and limited conversation to collaborators Dec 11, 2022

gopherbot added the FrozenDueToAge label Dec 11, 2022

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cmd/go: Program exits abruptly with the 語 character #50105

cmd/go: Program exits abruptly with the 語 character #50105

gkamathe commented Dec 11, 2021 •

edited

seankhliao commented Dec 11, 2021

zyxkad commented Dec 11, 2021

gkamathe commented Dec 11, 2021

ianlancetaylor commented Dec 11, 2021

cmd/go: Program exits abruptly with the 語 character #50105

cmd/go: Program exits abruptly with the 語 character #50105

Comments

gkamathe commented Dec 11, 2021 • edited

seankhliao commented Dec 11, 2021

zyxkad commented Dec 11, 2021

gkamathe commented Dec 11, 2021

ianlancetaylor commented Dec 11, 2021

gkamathe commented Dec 11, 2021 •

edited