Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

wasm: reading from stdin fails with Windows #43913

Open
evanw opened this issue Jan 26, 2021 · 1 comment
Open

wasm: reading from stdin fails with Windows #43913

evanw opened this issue Jan 26, 2021 · 1 comment
Labels
arch-wasm WebAssembly issues NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. OS-Windows
Milestone
Unplanned

Comments

@evanw
Copy link

evanw commented Jan 26, 2021

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

$ go version
go version go1.15.7 windows/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
set GO111MODULE=
set GOARCH=wasm
set GOBIN=
set GOCACHE=C:\Users\User\AppData\Local\go-build
set GOENV=C:\Users\User\AppData\Roaming\go\env
set GOEXE=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\User\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=js
set GOPATH=C:\Users\User\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=c:\go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=c:\go\pkg\tool\windows_amd64
set GCCGO=gccgo
set GOWASM=
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=0
set GOMOD=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-fPIC -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\User\AppData\Local\Temp\go-build540642258=/tmp/go-build -gno-record-gcc-switches

What did you do?

Code:

package main

import "fmt"
import "io/ioutil"
import "os"

func main() {
	bytes, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		fmt.Printf("err is %q\n", err.Error())
	} else {
		fmt.Printf("stdin is %q\n", string(bytes))
	}
}

Build with:

C:\Users\User\Desktop>set GOROOT=js
C:\Users\User\Desktop>set GOARCH=wasm
C:\Users\User\Desktop>go build -o main.wasm main.go

What did you expect to see?

C:\Users\User\Desktop>echo abc | node c:\go\misc\wasm\wasm_exec.js main.wasm
stdin is "abc \r\n"

What did you see instead?

C:\Users\User\Desktop>echo abc | node c:\go\misc\wasm\wasm_exec.js main.wasm
panic: <object>

goroutine 6 [running]:
syscall.mapJSError(0x7ff8000100000015, 0x418128, 0x160f0008, 0x7ff8000100000011)
        c:/go/src/syscall/fs_js.go:552 +0x1e
syscall.fsCall.func1(0x0, 0x0, 0x432240, 0x3, 0x3, 0x418120, 0x40000430700)
        c:/go/src/syscall/fs_js.go:507 +0xb
syscall/js.handleEvent()
        c:/go/src/syscall/js/func.go:96 +0x24

This is due to a bug in node where fs.read behaves incorrectly on Windows. It returns an EOF error when it hits the end of the file (the <object> is the EOF error object). There are at least two reports including nodejs/node#35997 and nodejs/node#19831.

However, I'm reporting it here because a) this bug is really old so it's all over the place in the wild and b) I think it's easy for Go to work around. My suggested workaround is to treat an EOF error from fs.read as null which should both avoid the panic and match Go's behavior on Unix.
@seankhliao seankhliao added arch-wasm WebAssembly issues NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. OS-Windows labels Jan 26, 2021
@seankhliao seankhliao changed the title Reading from stdin fails with WebAssembly on Windows wasm: reading from stdin fails with Windows Jan 26, 2021
@codefromthecrypt
Copy link

I ran into this in a different case. the root issue is that the parser currently only works with objects that have "code" mappings here: https://github.com/golang/go/blob/go1.19beta1/src/syscall/fs_js.go#L548-L554

@seankhliao seankhliao added this to the Unplanned milestone Aug 27, 2022
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
arch-wasm WebAssembly issues NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. OS-Windows
Projects
None yet
Milestone
Unplanned
Development

No branches or pull requests
3 participants
@codefromthecrypt @evanw @seankhliao