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syscall/js: call of Value.Int on undefined on win32 using node.js 10.7.0 #26524

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DHowett opened this issue Jul 22, 2018 · 5 comments
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arch-wasm WebAssembly issues FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. OS-Windows

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@DHowett
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DHowett commented Jul 22, 2018

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

go version go1.11beta2 windows/amd64

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

% go1.11beta2 env
set GOARCH=wasm
set GOBIN=
set GOCACHE=C:\Users\Dustin\AppData\Local\go-build
set GOEXE=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOOS=js
set GOPATH=C:\Users\Dustin\Projects\go
set GOPROXY=
set GORACE=
set GOROOT=C:\Users\Dustin\sdk\go1.11beta2
set GOTMPDIR=
set GOTOOLDIR=C:\Users\Dustin\sdk\go1.11beta2\pkg\tool\windows_amd64
set GCCGO=gccgo
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 -fmessage-length=0 -fdebug-prefix-map=C:\Users\Dustin\AppData\Local\Temp\go-build711284174=/tmp/go-build -gno-record-gcc-switches

% node.exe --version
v10.7.0

What did you do?

% $Env:GOOS="js"; $Env:GOARCH="wasm"
% cat test.go
package main

import "fmt"

func main() {
        fmt.Println("vim-go")
}
% go1.11beta2 build -o test.wasm
% cp C:\Users\Dustin\sdk\go1.11beta2\misc\wasm\wasm_exec.js .
% node.exe wasm_exec.js test.wasm

What did you expect to see?

vim-go

What did you see instead?

panic: syscall/js: call of Value.Int on undefined

goroutine 1 [running]:
syscall/js.Value.float(0x7ff8000000000001, 0x2adde, 0x9, 0x7ff8000000000001)
        C:/Users/Dustin/sdk/go1.11beta2/src/syscall/js/js.go:306 +0x35
syscall/js.Value.Int(0x7ff8000000000001, 0x2afad)
        C:/Users/Dustin/sdk/go1.11beta2/src/syscall/js/js.go:318 +0x2

Surprisingly, the same wasm binary on the same version of node works correctly on Node on Linux:

% docker run -ti --rm -v ${PWD}:/n node:latest bash
root@dbc7fd32409d:/# uname
Linux
root@dbc7fd32409d:/# node --version
v10.7.0
root@dbc7fd32409d:/# node /n/wasm_exec.js /n/test.wasm
vim-go
@agnivade agnivade changed the title js/wasm build products fail to launch on win32 node.js 10.7.0 syscall/js: call of Value.Int on undefined on win32 using node.js 10.7.0 Jul 22, 2018
@agnivade agnivade added OS-Windows arch-wasm WebAssembly issues NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Jul 22, 2018
@agnivade
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The stack trace coming from syscall/js is itself a bit strange when the code does not use syscall/js at all. It seems like the nodejs windows environment is somehow operating on an undefined js.Value, which is not very clear from the stack trace.

@DHowett
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DHowett commented Jul 28, 2018

It turns out that (node) fs on Windows does not include constants for O_NONBLOCK and O_SYNC. The initializer here demands that they exist, and we panic during syscall.init if they don't.

This is sufficient to ensure that all constants are present:

diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index 02a753c..71200cb 100644
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -4,11 +4,21 @@
 
 (() => {
 	// Map web browser API and Node.js API to a single common API (preferring web standards over Node.js API).
+	const requiredFsConstants = { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1, O_NONBLOCK: -1, O_SYNC: -1 };
 	const isNodeJS = typeof process !== "undefined";
 	if (isNodeJS) {
 		global.require = require;
 		global.fs = require("fs");
 
+		Object.entries(requiredFsConstants).forEach(([key, value]) => {
+			if (!(key in global.fs.constants)) {
+				Object.defineProperty(global.fs.constants, key, {
+					value: value,
+					writable: false
+				});
+			}
+		});
+
 		const nodeCrypto = require("crypto");
 		global.crypto = {
 			getRandomValues(b) {
@@ -37,7 +47,7 @@
 
 		let outputBuf = "";
 		global.fs = {
-			constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1, O_NONBLOCK: -1, O_SYNC: -1 }, // unused
+			constants: requiredFsConstants, // unused
 			writeSync(fd, buf) {
 				outputBuf += decoder.decode(buf);
 				const nl = outputBuf.lastIndexOf("\n");

@DHowett
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DHowett commented Jul 28, 2018

(The comment that the constants are unused is also manifestly false 😄)

@agnivade
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Thanks for the analysis @DHowett ! Would you like to send a patch and then @neelance can take a look at it ?

@bradfitz - Does it make sense to run wasm builders on windows machines too so that we can weed out issues like this ?

@gopherbot
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Change https://golang.org/cl/126600 mentions this issue: syscall: remove support for O_NONBLOCK and O_SYNC on js/wasm

jeet-parekh pushed a commit to jeet-parekh/go that referenced this issue Jul 31, 2018
This commit removes O_NONBLOCK on js/wasm. O_SYNC can't be
removed, because it is referenced by the os package, so instead
its use returns an error.

On Windows, the options O_NONBLOCK and O_SYNC are not available
when opening a file with Node.js. This caused the initialization
of the syscall package to panic.

The simplest solution is to not support these two options on js/wasm
at all. Code written for js/wasm is supposed to be portable,
so platform-specific options should not be used.

Fixes golang#26524.

Change-Id: I366aa3cdcfa59dfa9dc513368259f363ca090f00
Reviewed-on: https://go-review.googlesource.com/126600
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
@golang golang locked and limited conversation to collaborators Jul 31, 2019
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