SyncMutex: 'Mutex could not be created' on Windows

[MacGritsch]

I have tested the sync-module and specially the SyncMutex-class on Windows (PHP 8.3.x X64 TS).
It worked fine but after around one day, creation of Mutex fails with the exception "Mutex could not be created".
Is this something known?
In sourcecode I see that CreateMutexA() is used on windows. There seems to be no call to GetLastError(), so no idea why it fails creating the Mutex.
Could this be added?
I can not compile the module for Windows by myself, but I compiled it on macos and there it works fine.

Thank you for your grat work!

[jjdunn]

Our project has been using Sync extension for many years with no problems. We did run into some problems creating the mutex. solution is to try again.

Here's our class that wraps the mutex:

class DRSyncMutex {
    //number of times to retry creation of mutex before giving up
    const MutexRetryLimit = 15;  

    /**
     * Sometimes creating a new Mutex fails, the C++ library result is never returned, so we don't know why.
     * Workaround is to attempt to gain a mutex a number of times.
    */
    
    private $_mutex; // hold the created mutex for lock/unlock
    /*
     * @return DRSyncMutex $this
     */
    public function __construct($mutexName) {
        $retryCount = 0;
        do {
            try {
                $mutex = new SyncMutex($mutexName); // parent constructor
            } catch (Exception $e) {
                // this cannot be recovered from, if we don't get a mutex in $retryCount, rethrow
                usleep(100000); // 100 msec = 0.1 seconds
            }
            $retryCount++;
            $hasMutex = isset($mutex) && $mutex instanceof SyncMutex;
        } while (!$hasMutex && self::MutexRetryLimit > $retryCount);

        if (!$hasMutex) {
            //retries failed - rethrow
            throw new Exception("Mutex /{$mutexName}/ could not be created");
        }
        
        $this->_mutex = $mutex;
        return $this;
    }
    
    public function lock ($wait = -1) {
        return $this->_mutex->lock($wait);
    }
    public function unlock ($all = false) {
        return $this->_mutex->unlock($all);
    }
}

sample usage:

$mutexName = 'example';
$mutex = new DRSyncMutex($mutexName);
if ($mutex->lock(3000)) {
	try {
		//...whatever code must be single-threaded...
	} catch (\Exception $e) {
		// .. appropriate exception-handling logic
	}
}
$mutex->unlock();

[MacGritsch]

OMG, I found the problem:
I only checked that the length of the name (less than MAX_PATH) but not if it contains a backslash.
And thats exactly the only forbidden character - see CreateMutexA.
The name was part of a subpath in the Windows form "sub\path".

I think a meaningful exception or at least the error-value would help others to see the same issue.