Add a flag for verifying generated bytecode

This flag is enabled by default in tests through inspecting the
assertion status on the GeneratedQueryStructure class. If assertions are
enabled, the byte code verification will be enabled, otherwise it is not
enabled. When running tests, assertions are enabled.

community/codegen/pom.xml

@@ -12,6 +12,7 @@
     <bundle.namespace>org.neo4j.codegen</bundle.namespace>
     <license-text.header>GPL-3-header.txt</license-text.header>
     <licensing.prepend.text>notice-gpl-prefix.txt</licensing.prepend.text>
+    <asm.version>5.2</asm.version>
   </properties>
 
   <modelVersion>4.0.0</modelVersion>
@@ -53,7 +54,21 @@ the relevant Commercial Agreement.
     <dependency>
       <groupId>org.ow2.asm</groupId>
       <artifactId>asm</artifactId>
-      <version>5.2</version>
+      <version>${asm.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm-util</artifactId>
+      <version>${asm.version}</version>
+      <scope>provided</scope>
+      <optional>true</optional>
+    </dependency>
+    <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm-analysis</artifactId>
+      <version>${asm.version}</version>
+      <scope>provided</scope>
+      <optional>true</optional>
     </dependency>
     <dependency>
       <groupId>org.apache.commons</groupId>

community/codegen/src/main/java/org/neo4j/codegen/bytecode/ByteCode.java

@@ -46,6 +46,7 @@ protected String name()
             return "BYTECODE";
         }
     };
+    public static final CodeGeneratorOption VERIFY_GENERATED_BYTECODE = load( "Verifier" );
 
     @Override
     public void applyTo( Object target )
@@ -55,4 +56,17 @@ public void applyTo( Object target )
             ((Configuration) target).withFlag( this );
         }
     }
+
+    private static CodeGeneratorOption load( String option )
+    {
+        try
+        {
+            return (CodeGeneratorOption) Class.forName( ByteCode.class.getName() + option )
+                    .getDeclaredMethod( "load" + option ).invoke( null );
+        }
+        catch ( Throwable e )
+        {
+            return BLANK_OPTION;
+        }
+    }
 }

community/codegen/src/main/java/org/neo4j/codegen/bytecode/ByteCodeChecker.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2002-2017 "Neo Technology,"
+ * Network Engine for Objects in Lund AB [http://neotechnology.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * Neo4j is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.neo4j.codegen.bytecode;
+
+import java.util.Collection;
+
+import org.neo4j.codegen.ByteCodes;
+import org.neo4j.codegen.CompilationFailureException;
+
+interface ByteCodeChecker
+{
+    void check( ClassLoader classpathLoader, Collection<ByteCodes> byteCodes ) throws CompilationFailureException;
+}

community/codegen/src/main/java/org/neo4j/codegen/bytecode/ByteCodeGenerator.java

@@ -19,7 +19,9 @@
  */
 package org.neo4j.codegen.bytecode;
 
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import org.neo4j.codegen.ByteCodes;
@@ -28,12 +30,12 @@
 import org.neo4j.codegen.CompilationFailureException;
 import org.neo4j.codegen.TypeReference;
 
-public class ByteCodeGenerator extends CodeGenerator
+class ByteCodeGenerator extends CodeGenerator
 {
     private final Configuration configuration;
     private final Map<TypeReference,ClassByteCodeWriter> classes = new HashMap<>();
 
-    public ByteCodeGenerator( ClassLoader parentClassLoader, Configuration configuration)
+    ByteCodeGenerator( ClassLoader parentClassLoader, Configuration configuration )
     {
         super( parentClassLoader );
         this.configuration = configuration;
@@ -58,6 +60,16 @@ protected ClassEmitter generate( TypeReference type, TypeReference base, TypeRef
 
     protected Iterable<? extends ByteCodes> compile( ClassLoader classpathLoader ) throws CompilationFailureException
     {
-        return classes.values().stream().map( ClassByteCodeWriter::toByteCodes )::iterator;
+        List<ByteCodes> byteCodes = new ArrayList<>( classes.size() );
+        for ( ClassByteCodeWriter writer : classes.values() )
+        {
+            byteCodes.add( writer.toByteCodes() );
+        }
+        ByteCodeChecker checker = configuration.bytecodeChecker();
+        if ( checker != null )
+        {
+            checker.check( classpathLoader, byteCodes );
+        }
+        return byteCodes;
     }
 }