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  • Book (or resource) on Java bytecode

    - by Andrea
    I am looking for some resources on the JVM bytecode. Ideally I would for a short book; something more than a blog post but not a 800 pages tome. If it is relevant, I am a Scala developer, not a Java one, although I know Java just fine. I would like something that allowed me to read JVM bytecode and answer questions such as: Why does the bytecode has to know about high level construct such as classes? Are subtyping relations still visible in bytecode? How does type erasure work exactly? How do Oracle and Dalvik bytecode differ, and what consequences does this have for, say, developing Android apps with Scala? How does the JVM manage the stack, and why exactly this creates issues with tail call elimination? and so on.

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  • Stand-alone Bytecode Verifier

    - by HH
    In my bytecode instrumentation project, I stumble frequently on VerifyErrors. However, the default java Verifier gives little information on which instruction resulted in the error (it only gives the method and a small message). Is there any stand-alone bytecode verifier which provides with a little more advanced help in locating the error, at least the precise instruction location? Thank you.

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  • How are Scala traits compiled into Java bytecode?

    - by Justin Ardini
    I have played around with Scala for a while now, and I know that traits can act as the Scala equivalent of both interfaces and abstract classes. Recently I've been wondering how exactly traits are compiled into Java bytecode. I found some short explanations that stated traits are compiled exactly like Java interfaces when possible, and interfaces with an additional class otherwise. I still don't understand, however, how Scala achieves class linearization, a feature not available in Java. Could anyone explain or provide a good source explains how traits compile to Java bytecode?

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  • Bytecode and Objects

    - by HH
    Hey everyone, I am working on a bytecode instrumentation project. Currently when handling objects, the verifier throws an error most of the time. So I would like to get things clear concerning rules with objects (I read the JVMS but couldn't find the answer I was looking for): I am instrumenting the NEW instruction: original bytecode NEW <MyClass> DUP INVOKESPECIAL <MyClass.<init>> after instrumentation NEW <MyClass> DUP INVOKESTATIC <Profiler.handleNEW> DUP INVOKESPECIAL <MyClass.<init>> Note that I added a call to Profiler.handleNEW() which takes as argument an object reference (the newly created object). The piece of code above throws a VerificationError. While if I don't add the INVOKESTATIC (leaving only the DUP), it doesn't. So what is the rule that I'm violating? I can duplicate an uninitialized reference but I can't pass it as parameter? I would appreciate any help. Thank you

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  • running jython bytecode using java

    - by noamtm
    It looks like I'm missing something. When using Jython to run my Python code in Java, Java bytecode files are generated (test.py - [email protected]). Can I run these classes directly using java? In other words, I want to make this: $ java test@py [additional cp args] work. The intent: writing Python code and not having to give away source code.

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  • Types in Bytecode

    - by HH
    Hey everyone, I've been working for some time on (Java) Bytecode, however, it had never occurred to me to ask why are some instructions typed? I understand that in an ADD operation, we need to distinguish between an integer addition and a FP addition (that's why we have IADD and FADD). However, why do we need to distinguish between ISTORE and FSTORE? They both involve the exact same operation, which is moving 32 bits from the stack to a local variable position? The only answer I can think of is for type-safety, to prevent this: (ILOAD, ILOAD, FADD). However, I believe that type-safety is already enforced at the Java language level. OK, the Class file format is not directly coupled with Java, so is this a way to enforce type-safety for languages that do not support it? Any thought? Thank you.

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  • Converting ANTLR AST to Java bytecode using ASM

    - by Nick
    I am currently trying to write my own compiler, targeting the JVM. I have completed the parsing step using Java classes generated by ANTLR, and have an AST of the source code to work from (An ANTLR "CommonTree", specifically). I am using ASM to simplify the generating of the bytecode. Could anyone give a broad overview of how to convert this AST to bytecode? My current strategy is to explore down the tree, generating different code depending on the current node (using "Tree.getType()"). The problem is that I can only recognise tokens from my lexer this way, rather than more complex patterns from the parser. Is there something I am missing, or am I simply approaching this wrong? Thanks in advance :)

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  • Is there a way in .NET to access the bytecode/IL/CLR that is currently running?

    - by Alix
    Hi. I'd like to have access to the bytecode that is currently running or about to run in order to detect certain instructions and take specific actions (depending the instructions). In short, I'd like to monitor the bytecode in order to add safety control. Is this possible? I know there are some AOP frameworks that notify you of specific events, like an access to a field or the invocation of a method, but I'd like to skip that extra layer and just look at all the bytecode myself, throughout the entire execution of the application. I've already looked at the following questions (...among many many others ;) ):     Preprocessing C# - Detecting Methods     What CLR/.NET bytecode tools exist? as well as several AOP frameworks (although not in great detail, since they don't seem to do quite what I need) and I'm familiar with Mono.Cecil. I appreciate alternative suggestions, but I don't want to introduce the overhead of an AOP framework when what I actually need is access to the bytecode, without all the stuff they add on top to make it more user-friendly (... admittedly very useful stuff when you don't want to go low-level). Thanks :)

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  • NHibernate.Bytecode.UnableToLoadProxyFactoryFactoryException

    - by Shane
    I have the following code set up in my Startup IDictionary properties = new Dictionary(); properties.Add("connection.driver_class", "NHibernate.Driver.SqlClientDriver"); properties.Add("dialect", "NHibernate.Dialect.MsSql2005Dialect"); properties.Add("proxyfactory.factory_class", "NNHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle"); properties.Add("connection.provider", "NHibernate.Connection.DriverConnectionProvider"); properties.Add("connection.connection_string", "Data Source=ZEUS;Initial Catalog=mydb;Persist Security Info=True;User ID=sa;Password=xxxxxxxx"); InPlaceConfigurationSource source = new InPlaceConfigurationSource(); source.Add(typeof(ActiveRecordBase), (IDictionary<string, string>) properties); Assembly asm = Assembly.Load("Repository"); Castle.ActiveRecord.ActiveRecordStarter.Initialize(asm, source); I am getting the following error: failed: NHibernate.Bytecode.UnableToLoadProxyFactoryFactoryException : Unable to load type 'NNHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle' during configuration of proxy factory class. Possible causes are: - The NHibernate.Bytecode provider assembly was not deployed. - The typeName used to initialize the 'proxyfactory.factory_class' property of the session-factory section is not well formed. I have read and read I am referecning the All the assemblies listed and I am at a total loss as what to try next. Castle.ActiveRecord.dll Castle.DynamicProxy2.dll Iesi.Collections.dll log4net.dll NHibernate.dll NHibernate.ByteCode.Castle.dll I am 100% sure the assembly is in the bin. Anyone have any ideas?

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  • Java: Is there a way to obtain the bytecode for a class at runtime?

    - by Adam Paynter
    In Java, is there a way (at runtime) to obtain the bytecode which defined a particular class? Put another way, is there a way to obtain the byte[] array passed to ClassLoader.defineClass(String name, byte[] b, int off, int len) when a particular class was loaded? I see that this method is declared final, so creating a custom ClassLoader to intercept class definitions seems out of the question. In the past, I have used the class's ClassLoader to obtain the bytecode via the getResourceAsStream(String) method, but I would prefer a more canonical solution.

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  • Dealing with Try/Catch Exceptions in Java bytecode? ("stack height inconsistent")

    - by Cogwirrel
    I am trying to do some error handling in java bytecode. I first tried to implement some catch-like subroutines, where I would check for the error condition, and jump to the appropriate subroutine, a little like: iconst_1 iconst_0 dup ifeq calldiverr goto enddivtest calldiverr: jsr divError enddivtest: idiv ...More instructions... divError: getstatic java/lang/System/out Ljava/io/PrintStream; ldc "Oh dear you divided by 0!" invokevirtual java/io/PrintStream/print(Ljava/lang/String;)V The problem with the above is that when I have multiple instructions that jump to this subroutine, I get an error message when running the bytecode, saying that the stack height is inconsistent. Perhaps using exceptions is the best way to get around this? From some googling I have found that you can create instances of Exception classes and initialise them with something like: new java/lang/Exception dup ldc "exception message!" invokespecial java/lang/Exception/<init>(Ljava/lang/String;)V I have also found that you can throw them with athrow and this seems ok. What is confusing me however is exactly how exceptions are caught. There seems to be a magical "Exception table" which glues the throwing and catching of exceptions together, but I do not know how to define one of these when writing bytecode from scratch (and assembling using Jasmin). Can somebody tell me the secret of creating an exception table? And possibly give me an example of exception handling that will assemble with jasmin?

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  • Is it possible to cache JSP bytecode to avoid recompiles w/ Tomcat?

    - by Computer Guru
    Hi, Is there any way of caching the bytecode for JSP webapps/ In particular, using Tomcat as the Java servlet? I'm getting really fed up of Tomcat taking up all the CPU for 10 minutes while it compiles 4 different webapps every time I restart it.... I'm already using Jikes to "speed up" the compiles, but it's really killing me. The code does not change unless the webapp is upgraded (very rarely), and I cannot believe that there is no way to cache the compiled java bytecode instead of recompiling it each and every time. I'd appreciate any advice on the matter!

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  • Using JRuby/Jython for Ruby/Python interoperability?

    - by dbr
    Quite-probably a silly question, as I don't know much about Java/Jython/JRuby/bytecode, but.. I stumbled across _why's unholy again today.. It allows you to output Python bytecode from Ruby code.. Basically allowing them to produce the same bytecode.. Jython outputs Java bytecode, as does JRuby.. Since these both compile to the same bytecode, does this mean you could potentially use any Python library from Ruby, and Ruby libraries from Python?

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  • Any C/C++ to non-native bytecode compiler/interpreters?

    - by Matt
    As the title indicates, are there any C/C++ bytecode compilers/interpreters? I'm writing an application in an interpreted language that depends on certain libraries that are fully cross-compilable (there are no special flags to indicate code changes during compilation for a certain platform) but are written in C and C++. Rather than shipping n-platform-specific-libs with each platform, it would be nice to ship one set of libs which are interpreted by one platform specific interpreter. Possible and/or available?

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  • Writing a Compiler for .net - IL or Bytecode?

    - by Michael Stum
    I'm currently diving into the inner workings of .net, which means IL. As an exercise, I want to build a brainf..k compiler for .net (yes, they already exist, but as said it's for learning purposes). For the moment I'm just writing some text files that contain .il and compile them with ilasm, which works. But I wonder if I could/should go one level deeper and write bytecode directly? My "concern" is the Windows PE Stuff when compiling an EXE - instead of ilasm I would need some sort of Bytecode linker that would take my MSIL/CIL bytecode and generate the PE Stuff for it? Or do compilers "only" compile their language to IL and execute ilasm? Is there a managed version of it that I can call/embed from my compiler?

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  • Alternatives to Java bytecode instrumentation

    - by Rafael Regis
    I'm starting a project that will have to instrument java applications for coverage purposes (definition-usage of variables, etc). It has to add trace statements and some logic to the application and maybe remove statements. I have searched for ways of instrument Java code and what I always find is about bytecode instrumentation. My question is: It's the only way to instrument Java applications? There is any other way to do that? What are the advantages of bytecode instrumentation over the others? I'll probably use the bytecode solution, but I want to know what are the problems with the other approaches (if any) to decide precisely. Thanks!

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  • Why do VMs need to be "stack machines" or "register machines" etc.?

    - by Prog
    (This is an extremely newbie-ish question). I've been studying a little about Virtual Machines. Turns out a lot of them are designed very similarly to physical or theoretical computers. I read that the JVM for example, is a 'stack machine'. What that means (and correct me if I'm wrong) is that it stores all of it's 'temporary memory' on a stack, and makes operations on this stack for all of it's opcodes. For example, the source code 2 + 3 will be translated to bytecode similar to: push 2 push 3 add My question is this: JVMs are probably written using C/C++ and such. If so, why doesn't the JVM execute the following C code: 2 + 3..? I mean, why does it need a stack, or in other VMs 'registers' - like in a physical computer? The underlying physical CPU takes care of all of this. Why don't VM writers simply execute the interpreted bytecode with 'usual' instructions in the language the VM is programmed with? Why do VMs need to emulate hardware, when the actual hardware already does this for us? Again, very newbie-ish questions. Thanks for your help

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  • Eclipse + Django: How to get bytecode output when python source files change?

    - by Sean Ochoa
    Whenever I change my python source files in my Django project, the .pyc files become out of date. Of course that's because I need to recompile them in order to test them through my local Apache web server. I would like to get around this manual process by employing some automatic means of compiling them on save, or on build through Eclipse, or something like that. What's the best and proper way to do this?

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  • Java bytecode compiler benchmarks

    - by Dave Jarvis
    Q.1. What free compiler produces the fastest executable Java bytecode? Q.2. What free virtual machine executes Java bytecode the fastest (on 64-bit multi-core CPUs)? Q.3. What other (currently active) compiler projects are missing from this list: http://www.ibm.com/developerworks/java/jdk/ http://gcc.gnu.org/java/ http://openjdk.java.net/groups/compiler/ http://java.sun.com/javase/downloads/ http://download.eclipse.org/eclipse/downloads/ Q.4. What performance improvements can compilers do that JITs cannot (or do not)? Q.5. Where are some recent benchmarks, comparisons, or shoot-outs (for Q1 or Q2)? Thank you!

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