Retrieving tagged services after the Symfony2 DIC has already been compiled

AggregatedTaggedServicesPass.php

<?php

namespace OpenSky\Bundle\MainBundle\DependencyInjection\Compiler;

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Reference;
use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;

class AggregatedTaggedServicesPass implements CompilerPassInterface
{
    /**
     * @see Symfony\Component\DependencyInjection\Compiler.CompilerPassInterface::process()
     */
    public function process(ContainerBuilder $container)
    {
        if (!$container->hasDefinition('tagged_service_holder')) {
            return;
        }

        $taggedServiceHolder = $container->getDefinition('tagged_service_holder');

        foreach ($container->findTaggedServiceIds('custom.tag') as $id => $attributes) {
            $taggedServiceHolder->addMethodCall('push', array(new Reference($id)));
        }
    }
}

example.php

<?php

/* Elsewhere in your container-aware code, you can simply iterate across the
 * tagged service holder (a SplDoublyLinkedList in this example) in lieu of
 * calling findTaggedServiceIds().
 */
foreach ($container->get('tagged_service_holder') as $taggedService) {
    // do something with the service
}

MainBundle.php

<?php

namespace OpenSky\Bundle\MainBundle;

use OpenSky\Bundle\MainBundle\DependencyInjection\Compiler\AggregatedTaggedServicesPass;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\HttpKernel\Bundle\Bundle;

class MainBundle extends Bundle
{
    /**
     * @see Symfony\Component\HttpKernel\Bundle.Bundle::registerExtensions()
     */
    public function registerExtensions(ContainerBuilder $container)
    {
        parent::registerExtensions($container);
        $container->addCompilerPass(new AggregatedTaggedServicesPass());
    }
}

MainExtension.php

<?php

namespace OpenSky\Bundle\MainBundle\DependencyInjection;

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Definition;
use Symfony\Component\DependencyInjection\Extension\Extension;

class MainExtension extends Extension
{
    public function configLoad($config, ContainerBuilder $container)
    {
        if (!$container->hasDefinition('tagged_service_holder')) {
            $taggedServiceHolder = new Definition();
            $taggedServiceHolder->setClass('SplDoublyLinkedList');
            $container->setDefinition('tagged_service_holder', $taggedServiceHolder);
        }
    }
}