Inconsistent outputs with fork in JIT

[YuanchengJiang]

Description

The following code:

<?php
$pid = pcntl_fork();
var_dump(pcntl_getcpu());
print("1\n");
class A {
    private function __call($strMethod, $arrArgs) {
        echo "In " . __METHOD__ . $strMethod . "(array(" . implode(',',$arrArgs) . "))\n";
    }
}
class B extends A {
    function test() {
        A::test1(1,'a');
    }
}
$b = new B();
$b->test();
?>

Resulted in this output:

int(%d)
1
int(%d)
1
In A::__calltest1(array(1,a))
In A::__calltest1(array(1,a))

But I expected this output instead:

int(%d)
1
In A::__calltest1(array(1,a))
int(%d)
1
In A::__calltest1(array(1,a))

To reproduce:

-d "zend_extension=/php-src/modules/opcache.so" -d "opcache.enable=1" -d "opcache.enable_cli=1" -d "opcache.jit=0115"

Not sure whether it is an expected feature? Also unsure about its impact.

PHP Version

nightly

Operating System

ubuntu 22.04

[nielsdos]

This is not related to JIT. What's happening here is that you fork the process and they both start writing to the same output stream. This can cause ordering races between the output. The same would happen with the equivalent C code.