diff --git a/CHANGELOG-4.0.md b/CHANGELOG-4.0.md
index 9deacb4981..c3af769a41 100644
--- a/CHANGELOG-4.0.md
+++ b/CHANGELOG-4.0.md
@@ -7,6 +7,15 @@ in 4.0 minor versions.
 To get the diff for a specific change, go to https://github.com/symfony/symfony/commit/XXX where XXX is the change hash
 To get the diff between two versions, go to https://github.com/symfony/symfony/compare/v4.0.0...v4.0.1
 
+* 4.0.6 (2018-03-05)
+
+ * bug #26393  [DI] Skip resource tracking if disabled (chalasr)
+ * bug #26403 fix the handling of timestamp in the MongoDBSessionHandler (hjanuschka)
+ * bug #26355 [DI] Fix missing "id" normalization when dumping the container (nicolas-grekas)
+ * bug #26368 [WebProfilerBundle] Fix Debug toolbar breaks app (xkobal)
+ * bug #26369 Use fill instead of style for svg colors (rpkamp)
+ * bug #26358 [FrameworkBundle] Silence "Failed to remove directory" on cache:clear (nicolas-grekas)
+
 * 4.0.5 (2018-03-01)
 
  * bug #26327 [Form][WCAG] Errors sign for people that do not see colors (Nyholm)
diff --git a/src/Symfony/Bridge/PhpUnit/CoverageListener.php b/src/Symfony/Bridge/PhpUnit/CoverageListener.php
index 79333fbd00..d41c26968f 100644
--- a/src/Symfony/Bridge/PhpUnit/CoverageListener.php
+++ b/src/Symfony/Bridge/PhpUnit/CoverageListener.php
@@ -18,3 +18,9 @@ if (class_exists('PHPUnit_Runner_Version') && version_compare(\PHPUnit_Runner_Ve
 } else {
     class_alias('Symfony\Bridge\PhpUnit\Legacy\CoverageListenerForV7', 'Symfony\Bridge\PhpUnit\CoverageListener');
 }
+
+if (false) {
+    class CoverageListener
+    {
+    }
+}
diff --git a/src/Symfony/Bridge/PhpUnit/SymfonyTestsListener.php b/src/Symfony/Bridge/PhpUnit/SymfonyTestsListener.php
index d46a79e00e..a753525b76 100644
--- a/src/Symfony/Bridge/PhpUnit/SymfonyTestsListener.php
+++ b/src/Symfony/Bridge/PhpUnit/SymfonyTestsListener.php
@@ -18,3 +18,9 @@ if (class_exists('PHPUnit_Runner_Version') && version_compare(\PHPUnit_Runner_Ve
 } else {
     class_alias('Symfony\Bridge\PhpUnit\Legacy\SymfonyTestsListenerForV7', 'Symfony\Bridge\PhpUnit\SymfonyTestsListener');
 }
+
+if (false) {
+    class SymfonyTestsListener
+    {
+    }
+}
diff --git a/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit b/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit
index 2f97e32e11..a549cd7da4 100755
--- a/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit
+++ b/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit
@@ -26,8 +26,13 @@ if (PHP_VERSION_ID >= 70200) {
     $PHPUNIT_VERSION = '4.8';
 }
 
+if ('composer.json' !== $COMPOSER_JSON = getenv('COMPOSER') ?: 'composer.json') {
+    putenv('COMPOSER=composer.json');
+    $_SERVER['COMPOSER'] = $_ENV['COMPOSER'] = 'composer.json';
+}
+
 $root = __DIR__;
-while (!file_exists($root.'/composer.json') || file_exists($root.'/DeprecationErrorHandler.php')) {
+while (!file_exists($root.'/'.$COMPOSER_JSON) || file_exists($root.'/DeprecationErrorHandler.php')) {
     if ($root === dirname($root)) {
         break;
     }
diff --git a/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_3_horizontal_layout.html.twig b/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_3_horizontal_layout.html.twig
index f0c4626daf..d6b08f7637 100644
--- a/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_3_horizontal_layout.html.twig
+++ b/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_3_horizontal_layout.html.twig
@@ -62,4 +62,4 @@ col-sm-10
             {{- form_errors(form) -}}
         </div>{#--#}
     </div>
-{%- endblock checkbox_row %}
\ No newline at end of file
+{%- endblock checkbox_row %}
diff --git a/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig b/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig
index a3484d9036..2acd7086b0 100644
--- a/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig
+++ b/src/Symfony/Bridge/Twig/Resources/views/Form/bootstrap_4_layout.html.twig
@@ -203,7 +203,13 @@
                 {% set label = name|humanize %}
             {%- endif -%}
         {%- endif -%}
-        <{{ element|default('label') }}{% if label_attr %}{% with { attr: label_attr } %}{{ block('attributes') }}{% endwith %}{% endif %}>{{ translation_domain is same as(false) ? label : label|trans({}, translation_domain) }}{{- form_errors(form) -}}</{{ element|default('label') }}>
+        <{{ element|default('label') }}{% if label_attr %}{% with { attr: label_attr } %}{{ block('attributes') }}{% endwith %}{% endif %}>{{ translation_domain is same as(false) ? label : label|trans({}, translation_domain) }}{% block form_label_errors %}{{- form_errors(form) -}}{% endblock form_label_errors %}</{{ element|default('label') }}>
+    {%- else -%}
+        {%- if errors|length > 0 -%}
+        <div id="{{ id }}_errors" class="mb-2">
+            {{- form_errors(form) -}}
+        </div>
+        {%- endif -%}
     {%- endif -%}
 {%- endblock form_label %}
 
@@ -261,12 +267,12 @@
 
 {% block form_errors -%}
     {%- if errors|length > 0 -%}
-        <div class="{% if form is not rootform %}invalid-feedback d-block{% else %}alert alert-danger{% endif %}">
-            <ul class="list-unstyled mb-0">
-                {%- for error in errors -%}
-                    <li><span class="initialism form-error-icon badge badge-danger">{{ 'Error'|trans({}, 'validators') }}</span> <span class="form-error-message">{{ error.message }}</span></li>
-                {%- endfor -%}
-            </ul>
-        </div>
+        <span class="{% if form is not rootform %}invalid-feedback d-block{% else %}alert alert-danger{% endif %}">
+            {%- for error in errors -%}
+                <span class="mb-0 d-block">
+                    <span class="initialism form-error-icon badge badge-danger">{{ 'Error'|trans({}, 'validators') }}</span> <span class="form-error-message">{{ error.message }}</span>
+                </span>
+            {%- endfor -%}
+        </span>
     {%- endif %}
 {%- endblock form_errors %}
diff --git a/src/Symfony/Bundle/SecurityBundle/Resources/views/Collector/security.html.twig b/src/Symfony/Bundle/SecurityBundle/Resources/views/Collector/security.html.twig
index 7d993fb1f5..096fadd0f8 100644
--- a/src/Symfony/Bundle/SecurityBundle/Resources/views/Collector/security.html.twig
+++ b/src/Symfony/Bundle/SecurityBundle/Resources/views/Collector/security.html.twig
@@ -317,7 +317,14 @@
                         </td>
                         <td>
                             {% if decision.attributes|length == 1 %}
-                                {{ decision.attributes|first }}
+                                {% set attribute = decision.attributes|first %}
+                                {% if attribute.expression is defined %}
+                                    Expression: <pre><code>{{ attribute.expression }}</code></pre>
+                                {% elseif attribute.type == 'string' %}
+                                    {{ attribute }}
+                                {% else %}
+                                     {{ profiler_dump(attribute) }}
+                                {% endif %}
                             {% else %}
                                 {{ profiler_dump(decision.attributes) }}
                             {% endif %}
diff --git a/src/Symfony/Bundle/SecurityBundle/Tests/Functional/UserPasswordEncoderCommandTest.php b/src/Symfony/Bundle/SecurityBundle/Tests/Functional/UserPasswordEncoderCommandTest.php
index 629ff18a0c..8d2e34aa20 100644
--- a/src/Symfony/Bundle/SecurityBundle/Tests/Functional/UserPasswordEncoderCommandTest.php
+++ b/src/Symfony/Bundle/SecurityBundle/Tests/Functional/UserPasswordEncoderCommandTest.php
@@ -86,7 +86,7 @@ class UserPasswordEncoderCommandTest extends WebTestCase
         $this->assertContains('Password encoding succeeded', $output);
 
         $encoder = new Argon2iPasswordEncoder();
-        preg_match('#  Encoded password\s+(\$argon2id\$[\w\d,=\$+\/]+={0,2})\s+#', $output, $matches);
+        preg_match('#  Encoded password\s+(\$argon2id?\$[\w\d,=\$+\/]+={0,2})\s+#', $output, $matches);
         $hash = $matches[1];
         $this->assertTrue($encoder->isPasswordValid($hash, 'password', null));
     }
diff --git a/src/Symfony/Component/BrowserKit/Client.php b/src/Symfony/Component/BrowserKit/Client.php
index 0beea40c4d..0f5c410a4b 100644
--- a/src/Symfony/Component/BrowserKit/Client.php
+++ b/src/Symfony/Component/BrowserKit/Client.php
@@ -79,7 +79,7 @@ abstract class Client
     }
 
     /**
-     * Sets the maximum number of requests that crawler can follow.
+     * Sets the maximum number of redirects that crawler can follow.
      *
      * @param int $maxRedirects
      */
@@ -90,7 +90,7 @@ abstract class Client
     }
 
     /**
-     * Returns the maximum number of requests that crawler can follow.
+     * Returns the maximum number of redirects that crawler can follow.
      *
      * @return int
      */
diff --git a/src/Symfony/Component/Config/Resource/ReflectionClassResource.php b/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
index c5b7abf896..bf8e5625ac 100644
--- a/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
+++ b/src/Symfony/Component/Config/Resource/ReflectionClassResource.php
@@ -148,12 +148,16 @@ class ReflectionClassResource implements SelfCheckingResourceInterface, \Seriali
             yield print_r($defaults, true);
         }
 
-        if ($class->isSubclassOf(EventSubscriberInterface::class)) {
+        if ($class->isAbstract() || $class->isInterface() || $class->isTrait()) {
+            return;
+        }
+
+        if (interface_exists(EventSubscriberInterface::class, false) && $class->isSubclassOf(EventSubscriberInterface::class)) {
             yield EventSubscriberInterface::class;
             yield print_r(\call_user_func(array($class->name, 'getSubscribedEvents')), true);
         }
 
-        if ($class->isSubclassOf(ServiceSubscriberInterface::class)) {
+        if (interface_exists(ServiceSubscriberInterface::class, false) && $class->isSubclassOf(ServiceSubscriberInterface::class)) {
             yield ServiceSubscriberInterface::class;
             yield print_r(\call_user_func(array($class->name, 'getSubscribedServices')), true);
         }
diff --git a/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php b/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php
index 00a7901f3a..9d61c9cd83 100644
--- a/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php
+++ b/src/Symfony/Component/Config/Tests/Util/XmlUtilsTest.php
@@ -55,7 +55,7 @@ class XmlUtilsTest extends TestCase
             XmlUtils::loadFile($fixtures.'valid.xml', array($mock, 'validate'));
             $this->fail();
         } catch (\InvalidArgumentException $e) {
-            $this->assertRegExp('/The XML file "[\w:\/\\\.-]+" is not valid\./', $e->getMessage());
+            $this->assertRegExp('/The XML file "[\w:\/\\\.~+-]+" is not valid\./', $e->getMessage());
         }
 
         $this->assertInstanceOf('DOMDocument', XmlUtils::loadFile($fixtures.'valid.xml', array($mock, 'validate')));
diff --git a/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php b/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
index 5ece0fa4a5..9a109e8a1c 100644
--- a/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
+++ b/src/Symfony/Component/DependencyInjection/Dumper/PhpDumper.php
@@ -935,9 +935,13 @@ EOF;
 
         if (Container::class !== $baseClassWithNamespace) {
             $r = $this->container->getReflectionClass($baseClassWithNamespace, false);
-
-            if (null !== $r && (null !== $constructor = $r->getConstructor()) && 0 === $constructor->getNumberOfRequiredParameters()) {
-                $code .= "        parent::__construct();\n\n";
+            if (null !== $r
+                && (null !== $constructor = $r->getConstructor())
+                && 0 === $constructor->getNumberOfRequiredParameters()
+                && Container::class !== $constructor->getDeclaringClass()->name
+            ) {
+                $code .= "        parent::__construct();\n";
+                $code .= "        \$this->parameterBag = null;\n\n";
             }
         }
 
@@ -1619,7 +1623,7 @@ EOF;
 
     private function dumpParameter(string $name): string
     {
-        if ($this->container->isCompiled() && $this->container->hasParameter($name)) {
+        if ($this->container->hasParameter($name)) {
             $value = $this->container->getParameter($name);
             $dumpedValue = $this->dumpValue($value, false);
 
diff --git a/src/Symfony/Component/DependencyInjection/Tests/EnvVarProcessorTest.php b/src/Symfony/Component/DependencyInjection/Tests/EnvVarProcessorTest.php
new file mode 100644
index 0000000000..b1ee044e9e
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/EnvVarProcessorTest.php
@@ -0,0 +1,304 @@
+<?php
+
+namespace Symfony\Component\DependencyInjection\Tests;
+
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\DependencyInjection\Container;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\EnvVarProcessor;
+
+class EnvVarProcessorTest extends TestCase
+{
+    const TEST_CONST = 'test';
+
+    /**
+     * @dataProvider validStrings
+     */
+    public function testGetEnvString($value, $processed)
+    {
+        $container = new ContainerBuilder();
+        $container->setParameter('env(foo)', $value);
+        $container->compile();
+
+        $processor = new EnvVarProcessor($container);
+
+        $result = $processor->getEnv('string', 'foo', function () {
+            $this->fail('Should not be called');
+        });
+
+        $this->assertSame($processed, $result);
+    }
+
+    public function validStrings()
+    {
+        return array(
+            array('hello', 'hello'),
+            array('true', 'true'),
+            array('false', 'false'),
+            array('null', 'null'),
+            array('1', '1'),
+            array('0', '0'),
+            array('1.1', '1.1'),
+            array('1e1', '1e1'),
+        );
+    }
+
+    /**
+     * @dataProvider validBools
+     */
+    public function testGetEnvBool($value, $processed)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $result = $processor->getEnv('bool', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return $value;
+        });
+
+        $this->assertSame($processed, $result);
+    }
+
+    public function validBools()
+    {
+        return array(
+            array('true', true),
+            array('false', false),
+            array('null', false),
+            array('1', true),
+            array('0', false),
+            array('1.1', true),
+            array('1e1', true),
+        );
+    }
+
+    /**
+     * @dataProvider validInts
+     */
+    public function testGetEnvInt($value, $processed)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $result = $processor->getEnv('int', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return $value;
+        });
+
+        $this->assertSame($processed, $result);
+    }
+
+    public function validInts()
+    {
+        return array(
+            array('1', 1),
+            array('1.1', 1),
+            array('1e1', 10),
+        );
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExceptionMessage Non-numeric env var
+     * @dataProvider invalidInts
+     */
+    public function testGetEnvIntInvalid($value)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('int', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return $value;
+        });
+    }
+
+    public function invalidInts()
+    {
+        return array(
+            array('foo'),
+            array('true'),
+            array('null'),
+        );
+    }
+
+    /**
+     * @dataProvider validFloats
+     */
+    public function testGetEnvFloat($value, $processed)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $result = $processor->getEnv('float', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return $value;
+        });
+
+        $this->assertSame($processed, $result);
+    }
+
+    public function validFloats()
+    {
+        return array(
+            array('1', 1.0),
+            array('1.1', 1.1),
+            array('1e1', 10.0),
+        );
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExceptionMessage Non-numeric env var
+     * @dataProvider invalidFloats
+     */
+    public function testGetEnvFloatInvalid($value)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('float', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return $value;
+        });
+    }
+
+    public function invalidFloats()
+    {
+        return array(
+            array('foo'),
+            array('true'),
+            array('null'),
+        );
+    }
+
+    /**
+     * @dataProvider validConsts
+     */
+    public function testGetEnvConst($value, $processed)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $result = $processor->getEnv('const', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return $value;
+        });
+
+        $this->assertSame($processed, $result);
+    }
+
+    public function validConsts()
+    {
+        return array(
+            array('Symfony\Component\DependencyInjection\Tests\EnvVarProcessorTest::TEST_CONST', self::TEST_CONST),
+            array('E_ERROR', E_ERROR),
+        );
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExceptionMessage undefined constant
+     * @dataProvider invalidConsts
+     */
+    public function testGetEnvConstInvalid($value)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('const', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return $value;
+        });
+    }
+
+    public function invalidConsts()
+    {
+        return array(
+            array('Symfony\Component\DependencyInjection\Tests\EnvVarProcessorTest::UNDEFINED_CONST'),
+            array('UNDEFINED_CONST'),
+        );
+    }
+
+    public function testGetEnvBase64()
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $result = $processor->getEnv('base64', 'foo', function ($name) {
+            $this->assertSame('foo', $name);
+
+            return base64_encode('hello');
+        });
+
+        $this->assertSame('hello', $result);
+    }
+
+    public function testGetEnvJson()
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $result = $processor->getEnv('json', 'foo', function ($name) {
+            $this->assertSame('foo', $name);
+
+            return json_encode(array(1));
+        });
+
+        $this->assertSame(array(1), $result);
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExceptionMessage Syntax error
+     */
+    public function testGetEnvInvalidJson()
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('json', 'foo', function ($name) {
+            $this->assertSame('foo', $name);
+
+            return 'invalid_json';
+        });
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExceptionMessage Invalid JSON env var
+     * @dataProvider otherJsonValues
+     */
+    public function testGetEnvJsonOther($value)
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('json', 'foo', function ($name) use ($value) {
+            $this->assertSame('foo', $name);
+
+            return json_encode($value);
+        });
+    }
+
+    public function otherJsonValues()
+    {
+        return array(
+            array(1),
+            array(1.1),
+            array(true),
+            array(false),
+        );
+    }
+
+    /**
+     * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
+     * @expectedExceptionMessage Unsupported env var prefix
+     */
+    public function testGetEnvUnknown()
+    {
+        $processor = new EnvVarProcessor(new Container());
+
+        $processor->getEnv('unknown', 'foo', function ($name) {
+            $this->assertSame('foo', $name);
+
+            return 'foo';
+        });
+    }
+}
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Container/NoConstructorContainer.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Container/NoConstructorContainer.php
index 7514cc7c1b..b14b013f1f 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Container/NoConstructorContainer.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/Container/NoConstructorContainer.php
@@ -2,6 +2,8 @@
 
 namespace Symfony\Component\DependencyInjection\Tests\Fixtures\Container;
 
-class NoConstructorContainer
+use Symfony\Component\DependencyInjection\Container;
+
+class NoConstructorContainer extends Container
 {
 }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_constructor_without_arguments.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_constructor_without_arguments.php
index 01caae6489..a6b9962b3d 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_constructor_without_arguments.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_constructor_without_arguments.php
@@ -29,6 +29,7 @@ class ProjectServiceContainer extends \Symfony\Component\DependencyInjection\Tes
     public function __construct()
     {
         parent::__construct();
+        $this->parameterBag = null;
 
         $this->services = $this->privates = array();
 
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_with_optional_constructor_arguments.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_with_optional_constructor_arguments.php
index 1c20741bf7..84986f1638 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_with_optional_constructor_arguments.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/custom_container_class_with_optional_constructor_arguments.php
@@ -29,6 +29,7 @@ class ProjectServiceContainer extends \Symfony\Component\DependencyInjection\Tes
     public function __construct()
     {
         parent::__construct();
+        $this->parameterBag = null;
 
         $this->services = $this->privates = array();
 
diff --git a/src/Symfony/Component/DomCrawler/Field/FormField.php b/src/Symfony/Component/DomCrawler/Field/FormField.php
index 567164d046..33c0bbeac0 100644
--- a/src/Symfony/Component/DomCrawler/Field/FormField.php
+++ b/src/Symfony/Component/DomCrawler/Field/FormField.php
@@ -75,8 +75,6 @@ abstract class FormField
         if ($labels->length > 0) {
             return $labels->item(0);
         }
-
-        return;
     }
 
     /**
diff --git a/src/Symfony/Component/Form/Tests/AbstractBootstrap4HorizontalLayoutTest.php b/src/Symfony/Component/Form/Tests/AbstractBootstrap4HorizontalLayoutTest.php
index e8ede167b3..c906c6549a 100644
--- a/src/Symfony/Component/Form/Tests/AbstractBootstrap4HorizontalLayoutTest.php
+++ b/src/Symfony/Component/Form/Tests/AbstractBootstrap4HorizontalLayoutTest.php
@@ -32,14 +32,12 @@ abstract class AbstractBootstrap4HorizontalLayoutTest extends AbstractBootstrap4
     [
         ./label[@for="name"]
         [
-            ./div[
-                ./ul
-                    [./li
-                        [./span[.="[trans]Error[/trans]"]]
-                        [./span[.="[trans]Error![/trans]"]]
-                    ]
-                    [count(./li)=1]
-            ]
+            ./span[@class="alert alert-danger"]
+                [./span[@class="mb-0 d-block"]
+                    [./span[.="[trans]Error[/trans]"]]
+                    [./span[.="[trans]Error![/trans]"]]
+                ]
+                [count(./span)=1]
         ]
         /following-sibling::div[./input[@id="name"]]
     ]
diff --git a/src/Symfony/Component/Form/Tests/AbstractBootstrap4LayoutTest.php b/src/Symfony/Component/Form/Tests/AbstractBootstrap4LayoutTest.php
index ec97577818..6e448c413a 100644
--- a/src/Symfony/Component/Form/Tests/AbstractBootstrap4LayoutTest.php
+++ b/src/Symfony/Component/Form/Tests/AbstractBootstrap4LayoutTest.php
@@ -32,14 +32,12 @@ abstract class AbstractBootstrap4LayoutTest extends AbstractBootstrap3LayoutTest
     [
         ./label[@for="name"]
         [
-            ./div[
-                ./ul
-                    [./li
-                        [./span[.="[trans]Error[/trans]"]]
-                        [./span[.="[trans]Error![/trans]"]]
-                    ]
-                    [count(./li)=1]
-            ]
+            ./span[@class="alert alert-danger"]
+                [./span[@class="mb-0 d-block"]
+                    [./span[.="[trans]Error[/trans]"]]
+                    [./span[.="[trans]Error![/trans]"]]
+                ]
+                [count(./span)=1]
         ]
         /following-sibling::input[@id="name"]
     ]
@@ -162,26 +160,32 @@ abstract class AbstractBootstrap4LayoutTest extends AbstractBootstrap3LayoutTest
         $html = $this->renderErrors($view);
 
         $this->assertMatchesXpath($html,
-'/div
+'/span
     [@class="alert alert-danger"]
     [
-        ./ul
-            [@class="list-unstyled mb-0"]
-            [
-                ./li
-                    [./span[.="[trans]Error[/trans]"]]
-                    [./span[.="[trans]Error 1[/trans]"]]
-                  
-                /following-sibling::li
-                    [./span[.="[trans]Error[/trans]"]]
-                    [./span[.="[trans]Error 2[/trans]"]]
-            ]
-            [count(./li)=2]
+        ./span[@class="mb-0 d-block"]
+            [./span[.="[trans]Error[/trans]"]]
+            [./span[.="[trans]Error 1[/trans]"]]
+          
+        /following-sibling::span[@class="mb-0 d-block"]
+            [./span[.="[trans]Error[/trans]"]]
+            [./span[.="[trans]Error 2[/trans]"]]    
     ]
+    [count(./span)=2]
 '
         );
     }
 
+    public function testErrorWithNoLabel()
+    {
+        $form = $this->factory->createNamed('name', 'Symfony\Component\Form\Extension\Core\Type\TextType', array('label'=>false));
+        $form->addError(new FormError('[trans]Error 1[/trans]'));
+        $view = $form->createView();
+        $html = $this->renderLabel($view);
+
+        $this->assertMatchesXpath($html, '//span[.="[trans]Error[/trans]"]');
+    }
+
     public function testCheckedCheckbox()
     {
         $form = $this->factory->createNamed('name', 'Symfony\Component\Form\Extension\Core\Type\CheckboxType', true);
diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MemcachedSessionHandler.php b/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MemcachedSessionHandler.php
index 9f4ef7028e..dd37eae14e 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MemcachedSessionHandler.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MemcachedSessionHandler.php
@@ -80,7 +80,9 @@ class MemcachedSessionHandler extends AbstractSessionHandler
      */
     public function updateTimestamp($sessionId, $data)
     {
-        return $this->memcached->touch($this->prefix.$sessionId, time() + $this->ttl);
+        $this->memcached->touch($this->prefix.$sessionId, time() + $this->ttl);
+
+        return true;
     }
 
     /**
diff --git a/src/Symfony/Component/HttpKernel/KernelInterface.php b/src/Symfony/Component/HttpKernel/KernelInterface.php
index e58fbd2ed5..925e37b071 100644
--- a/src/Symfony/Component/HttpKernel/KernelInterface.php
+++ b/src/Symfony/Component/HttpKernel/KernelInterface.php
@@ -18,7 +18,7 @@ use Symfony\Component\Config\Loader\LoaderInterface;
 /**
  * The Kernel is the heart of the Symfony system.
  *
- * It manages an environment made of bundles.
+ * It manages an environment made of application kernel and bundles.
  *
  * @author Fabien Potencier <fabien@symfony.com>
  */
@@ -27,7 +27,7 @@ interface KernelInterface extends HttpKernelInterface, \Serializable
     /**
      * Returns an array of bundles to register.
      *
-     * @return BundleInterface[] An array of bundle instances
+     * @return iterable|BundleInterface[] An iterable of bundle instances
      */
     public function registerBundles();
 
@@ -67,7 +67,7 @@ interface KernelInterface extends HttpKernelInterface, \Serializable
     public function getBundle($name);
 
     /**
-     * Returns the file path for a given resource.
+     * Returns the file path for a given bundle resource.
      *
      * A Resource can be a file or a directory.
      *
diff --git a/src/Symfony/Component/HttpKernel/Resources/welcome.html.php b/src/Symfony/Component/HttpKernel/Resources/welcome.html.php
index d8c37beb56..caac7fd6eb 100644
--- a/src/Symfony/Component/HttpKernel/Resources/welcome.html.php
+++ b/src/Symfony/Component/HttpKernel/Resources/welcome.html.php
@@ -76,7 +76,7 @@
     </div>
     <div id="comment">
         <p>
-            You're seeing this message because you have debug mode enabled and you haven't configured any URLs.
+            You're seeing this page because debug mode is enabled and you haven't configured any homepage URL.
         </p>
     </div>
 </div>
diff --git a/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php b/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php
index aa8f61cc8b..72804699ea 100644
--- a/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php
+++ b/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php
@@ -193,11 +193,10 @@ EOF
             }
         }
 
-        if ('' === $code) {
-            $code .= "        if ('/' === \$pathinfo) {\n";
-            $code .= "            throw new Symfony\Component\Routing\Exception\NoConfigurationException();\n";
-            $code .= "        }\n";
-        }
+        // used to display the Welcome Page in apps that don't define a homepage
+        $code .= "        if ('/' === \$pathinfo) {\n";
+        $code .= "            throw new Symfony\Component\Routing\Exception\NoConfigurationException();\n";
+        $code .= "        }\n";
 
         return $code;
     }
diff --git a/src/Symfony/Component/Routing/Matcher/UrlMatcher.php b/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
index e37cae0361..3862d7d42e 100644
--- a/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
+++ b/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
@@ -88,7 +88,7 @@ class UrlMatcher implements UrlMatcherInterface, RequestMatcherInterface
             return $ret;
         }
 
-        if (0 === count($this->routes) && '/' === $pathinfo) {
+        if ('/' === $pathinfo) {
             throw new NoConfigurationException();
         }
 
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php
index 97a544b7ba..21dfd7fc24 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php
@@ -238,6 +238,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher10.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher10.php
index 4166936568..2a97138ba6 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher10.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher10.php
@@ -2821,6 +2821,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher11.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher11.php
index 2167b4e917..dd348f57ce 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher11.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher11.php
@@ -146,6 +146,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         return null;
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher12.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher12.php
index be3d1f4373..30767d1410 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher12.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher12.php
@@ -91,6 +91,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher13.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher13.php
index f31a0544fe..e0b441d86a 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher13.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher13.php
@@ -60,6 +60,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php
index acffa8e6a2..96ed00cc81 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php
@@ -275,6 +275,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         return null;
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher3.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher3.php
index fc5c9853a2..a3b280fe9a 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher3.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher3.php
@@ -103,6 +103,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher4.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher4.php
index a5ea6c6276..feecc9df27 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher4.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher4.php
@@ -75,6 +75,10 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 return $ret;
         }
 
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
+
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
 }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher5.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher5.php
index 152cc61cec..a6536ef6a3 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher5.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher5.php
@@ -145,6 +145,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         return null;
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher6.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher6.php
index 960e20157d..3a9f9baf81 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher6.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher6.php
@@ -122,6 +122,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher7.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher7.php
index 591b526c14..ccb32ebb75 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher7.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher7.php
@@ -157,6 +157,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         return null;
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher8.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher8.php
index 0e1d0c8e95..fc20bbfffb 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher8.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher8.php
@@ -79,6 +79,9 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 $offset += strlen($m);
             }
         }
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
 
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher9.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher9.php
index c459408d70..28f3f36d17 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher9.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher9.php
@@ -44,6 +44,10 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
                 break;
         }
 
+        if ('/' === $pathinfo) {
+            throw new Symfony\Component\Routing\Exception\NoConfigurationException();
+        }
+
         throw $allow ? new MethodNotAllowedException(array_keys($allow)) : new ResourceNotFoundException();
     }
 }
diff --git a/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
index b4e8e46dc2..c9a7da9b81 100644
--- a/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
@@ -34,7 +34,6 @@ abstract class AbstractObjectNormalizer extends AbstractNormalizer
 {
     const ENABLE_MAX_DEPTH = 'enable_max_depth';
     const DEPTH_KEY_PATTERN = 'depth_%s::%s';
-    const ALLOW_EXTRA_ATTRIBUTES = 'allow_extra_attributes';
     const DISABLE_TYPE_ENFORCEMENT = 'disable_type_enforcement';
 
     private $propertyTypeExtractor;