Crash on windows when passing child process' stdin as other childs stdout

[mika-fischer]

• Version: v8.9.2
• Platform: Windows 10 64bits

The following simple test crashes the node process on Windows. It works fine on Linux.

const {spawn} = require('child_process');

if (process.argv.length <= 2) {
    // parent
    const child2 = spawn(process.argv0, [process.argv[1], '.'], {
        stdio: ['pipe', 'ignore', 'ignore'],
    });
    const child1 = spawn(process.argv0, [process.argv[1], '.'], {
        stdio: ['pipe', child2.stdin, 'ignore'],
    });
    setInterval(() => child1.stdin.write(`.`), 1);
} else {
    // children
    process.stdin.pipe(process.stdout);
}

The error is:

Exception thrown: write access violation.
req was 0x2275CA37430.

It occurs in deps/uv/src/win/core.c:439.

Call stack:

Locals:

I got the stack traces from a self-compiled build, but it also crashes with the official binary.

[bzoz]

@mika-fischer I can't reproduce this. I'm trying this with Node 8.9.2 (but also with 8.6.0 and latest nightly) on 64-bit Win 10 Pro and it works. Are you maybe redirecting the script output somewhere or using some other terminal (like ConEmu)?

[mika-fischer]

I've tried it in plain cmd, cmder, VS2015 x64 Native Command Prompt and cmd inside VSCode. And of course it's best to run it in the debugger. In all those cases it always crashes for me.

So if you run it in the debugger with devenv /debugexe apps\node\Debug\node.exe tests\nodejs-process-pipe\bug.js it just continues running?

[bzoz]

I did not test this correctly, it does indeed crash.

I've tested, this reproduces back to v6 (on v4 there is a TypeError when spawning child2).

I've made slightly modified version of your code which still reproduces:

const writeSize = 1

const spawn = require('child_process').spawn;

const who = process.argv.length <= 2 ? 'parent' : process.argv[2];


switch (who) {
    case 'parent':
        const consumer = spawn(process.argv0, [process.argv[1], 'consumer'], {
            stdio: ['pipe', 'ignore', 'inherit'],
        });
        const producer = spawn(process.argv0, [process.argv[1], 'producer'], {
            stdio: ['pipe', consumer.stdin, 'inherit'],
        });
        process.stdin.on('data', () => {})
        break
    case 'producer':
        const buffer = Buffer.alloc(writeSize, '.');
        const write = () => {
            process.stdout.write(buffer, write);
        }
        write()
        break
    case 'consumer':
        var totalDots = 0;
        process.stdin.on('data', (data) => {
            totalDots += data.length
            console.error(`Got ${data.length} dots! Total: ${totalDots}`)
        })
        break
}

The consumer will receive data from the producer so that part works. But then, it will crash at random point, between 600 and 900 bytes written.

If you change writeSize to about 1000, it will crash either:

• instantly
• after one write
• after two writes, where the second one is much bigger:
  

This looks like a race inside libuv, I'll investigate this further.

[seishun]

Can't reproduce on master. It was probably fixed in #18260.

[bzoz]

It was fixed in #18019. Maybe we should add this as a test to Node.js?

[cjihrig]

@bzoz a regression test is a good idea.

[bzoz]

Test in #18614