await() error in SimpleFiber.php

[szado]

(Great job with Fibers initiative!)
For test purposes I'm refactoring my app with await() function in place of promises-chains. I've got an error:

2021-11-29 21:56:23 [EXCEPTION] Error: Value of type null is not callable in ...\vendor\react\async\src\SimpleFiber.php:59
2021-11-29 21:56:23 [EXCEPTION] #0 ...\vendor\react\async\src\functions.php(92): React\Async\SimpleFiber->suspend()
2021-11-29 21:56:23 [EXCEPTION] #1 ...\MessagesProcessor.php(114): React\Async\await(Object(React\Promise\Promise))

It occurs when I try to use async() function. It's hard to say how to reproduce this bug. In the same call stack, a few promises before, I use a React\Http\Browser with async() function. If I comment this usage (replace to something like resolve(new ResultObject())) - error doesn't occur. If I use Browser with promise-style api, the PHP process ends with error:

Process finished with exit code -1073741819 (0xC0000005)

I'm using the newest versions of all packages, ofc PHP 8.1.
Do you know what can cause these errors?

[szado]

This code causes Segmentation fault error (CLI on Windows):

<?php
require 'vendor/autoload.php';
$browser = new \React\Http\Browser();
/** @var \Psr\Http\Message\ResponseInterface $response */
$response = \React\Async\await($browser->get('https://github.com'));
var_dump((string)$response->getBody());

...but only for "github.com", for "google.com" returns proper result.
This works fine in both cases:

<?php
require 'vendor/autoload.php';
$browser = new \React\Http\Browser();
$browser
    ->get('https://github.com')
    ->then(fn (\Psr\Http\Message\ResponseInterface $response) => var_dump((string)$response->getBody()));

EDIT:
Problem exists only on Windows PHP compilation - on linux all works correctly.
EDIT2:
Please check it for yourself on your environment, on my it's not predictable. Yesterday it worked, now it doesn't - in CLI I have segmentation fault.

[clue]

@szado Thank you for reporting, this definitely shouldn't have happened!

I've tried reproducing this a number of times, but can not reproduce the problem you're seeing on Linux.

A segmentation fault is not something that userland PHP code should be able to trigger. There is also no platform-specific code in ReactPHP involved, so I can only suspect this is an issue with the fibers implementation in PHP itself. I don't think this boils down to an issue in ReactPHP itself, so I wonder if we can break this down to a reproducible script that also shows this segmentation fault without ReactPHP?

Accordingly, it looks like this should probably be reported upstream in PHP. Can anybody take a look at this and link/report back here?

Thank you!

[szado]

@clue maybe this code will be helpful: https://github.com/szado/reactphp-connection-pool/blob/master/test.php
It triggers Segmentation fault and Error: Value of type null is not callable in ...\reactphp-connection-pool\vendor\react\async\src\SimpleFiber.php on line 59 (it can be more directly related to ReactPHP) on Windows and Linux.

[Revalto]

Tested on both Windows and Linux, I didn't notice any difference. The error is present both there and there.

Here is my piece of code. I'm trying to wait for a WebSocket response and give it back. As a result, I get an error. If you don't wait for an answer, but just give out any value, everything goes well

return new Promise(function (callable $resolve) {
  ReplyRoute::reply('Server:GetValue', function (int $value) use ($resolve) {
      $resolve($value); // Error
  });

  $resolve(100); // Good
});

[WyriHaximus]

@szado I can reproduce that error and looking into the exact cause (probably related to PHP Fatal error: Uncaught TypeError: Szado\React\ConnectionPool\ConnectionPool::retryWithDelay(): Return value must be of type Szado\React\ConnectionPool\ConnectionAdapters\ConnectionAdapterInterface, null returned) and then work on a fix.
The browser segfault I can't reproduce on windows. But might be the same root cause internally.

[bartvanhoutte]

Ran into the same error.

<?php

use React\Promise\Promise;
use React\Promise\PromiseInterface;

use function React\Async\await;
use function React\Promise\resolve;

require_once __DIR__ . '/vendor/autoload.php';

function test(): PromiseInterface {
    $resolver = function ($resolve, $reject) {
      await(resolve());

      $resolve();
    };

    return new Promise($resolver);
}

await(test());

[docker://fiber:latest/]:php /opt/project/index.php

Fatal error: Uncaught Error: Value of type null is not callable in /opt/project/vendor/react/async/src/SimpleFiber.php on line 59

Error: Value of type null is not callable in /opt/project/vendor/react/async/src/SimpleFiber.php on line 59

Call Stack:
    0.0002     391640   1. {main}() /opt/project/index.php:0
    0.0886    4169192   2. React\Async\await($promise = class React\Promise\Promise { private $canceller = NULL; private $result = NULL; private $handlers = [0 => class Closure { virtual $closure = "React\Promise\Promise::React\Promise\{closure}", ... }]; private $progressHandlers = [0 => class Closure { virtual $closure = "React\Promise\Promise::React\Promise\{closure}", ... }]; private $requiredCancelRequests = 0; private $cancelRequests = 0 }) /opt/project/index.php:19
    0.0886    4174816   3. React\Async\SimpleFiber->suspend() /opt/project/vendor/react/async/src/functions.php:89

[WyriHaximus]

TL;DR You're only having one fiber (the main fiber) running and you want to await for a promise twice, it's simply not possible.

[WyriHaximus]

P.S. Will get you a longer response somewhere between tonight and the end of the weekend. Working on a bunch of examples and a blog post on this.

[bartvanhoutte]

@WyriHaximus 👌 It might lead to some unexpected errors when you're using a 3rd party library. Right now the example is pretty useless but replace await(resolve()) with some 3rd party function that undirectly calls await somewhere and you're stuck. Will try to find a workaround in my case.

[bartvanhoutte]

Something like this instead?

<?php

use React\Promise\PromiseInterface;

use function React\Async\async;
use function React\Async\await;
use function React\Promise\resolve;

require_once __DIR__ . '/vendor/autoload.php';

function test(): PromiseInterface {
    return async(function () {
      await(resolve());
    });
}

await(test());

[WyriHaximus]

@bartvanhoutte yes, each async will create a new fiber.

[WyriHaximus]

Just filed #18 that helps with a few cases mentioned in this issue. And intentionally all of them (except the segfault), but I'd have to test that