bytecode

How to verify Java Bytecode before injecting into the JVM?

孤人 提交于 2021-02-19 07:27:47
问题 I'm trying to verify "on the fly" generated bytecode! I already had several attempts, one attempt was to compile my classes in runtime with the eclipse compiler another was to compile from memory as mentioned here: Compile From Memory First results looked okay but I'm still not a 100% sure if the verification process is truly valid according to the JAVA 6 guidelines and security measurements as well to normal OOP Models. Any better way on how to verify bytecode? 回答1: If you load the generated

Why java bytecode from a class have come code for new staic inner class appear jvm instruction ACONST_NULL

喜欢而已 提交于 2021-02-19 06:11:25
问题 I try to new a inner staic class, But I find that bytecode appear the jvm instruction ACONST_NULL bwteen NEW , DUP and INVOKE_SPECIAL , But I know about a class new is NEW DUP INVOKE_SPECIAL package com.hoho.api; /** * @author linuxea */ public class Main { private static class InnerMain { // no field } public static void main(String[] args) { InnerMain innerMain = new InnerMain(); } } // class version 52.0 (52) // access flags 0x21 public class com/hoho/api/Main { // compiled from: Main.java

Why java bytecode from a class have come code for new staic inner class appear jvm instruction ACONST_NULL

无人久伴 提交于 2021-02-19 06:07:40
问题 I try to new a inner staic class, But I find that bytecode appear the jvm instruction ACONST_NULL bwteen NEW , DUP and INVOKE_SPECIAL , But I know about a class new is NEW DUP INVOKE_SPECIAL package com.hoho.api; /** * @author linuxea */ public class Main { private static class InnerMain { // no field } public static void main(String[] args) { InnerMain innerMain = new InnerMain(); } } // class version 52.0 (52) // access flags 0x21 public class com/hoho/api/Main { // compiled from: Main.java

Does nodejs/V8 store compiled machine code anywhere on disk?

£可爱£侵袭症+ 提交于 2021-02-18 10:46:12
问题 Edit : Node uses bytecode since Node 8.3, before that, sources were compiled directly to machine code. I do a lot of Python coding, and there's always bytecode lying around in .pyc files. I was wondering if node stores its machine code in similar files, eg it would make sense to keep the machine code representation around on disk and re-use it if a file's source is unchanged. If so, where does node/v8 store this machine code? Edit 2 : As @dystroy mentions below this is a dupe of How can I see

Why does Java code need to be compiled but JavaScript code does not

半腔热情 提交于 2021-02-17 21:24:05
问题 How come code written in Java needs to be compiled in byte-code that is interpreted by the JVM, but code written in a language like JavaScript does not need to be compiled and can run directly in a browser? Is there an easy way to understand this? What is the fundamental difference between the way these two languages are written, that may help to understand this behavior? I am not a CS student, so please excuse the naivete of the question. 回答1: Historically, JavaScript was an interpreted

Why does Java code need to be compiled but JavaScript code does not

不问归期 提交于 2021-02-17 21:21:35
问题 How come code written in Java needs to be compiled in byte-code that is interpreted by the JVM, but code written in a language like JavaScript does not need to be compiled and can run directly in a browser? Is there an easy way to understand this? What is the fundamental difference between the way these two languages are written, that may help to understand this behavior? I am not a CS student, so please excuse the naivete of the question. 回答1: Historically, JavaScript was an interpreted

unexplained 10%+ performance boost from simply adding a method argument (slimmer jit code)

泄露秘密 提交于 2021-02-17 19:13:07
问题 (note: proper answer must go beyond reproduction). After millions of invocations, quicksort1 is definitely faster than quicksort2, which have identical code aside from this 1 extra arg. The code is at the end of the post. Spoiler: I also found the jit code is fatter by 224 bytes even if it should be actually simpler (like the byte code size tells; see very last update below). Even after trying to factor out this effect with some microbenchmark harness (JMH), the performance difference is

unexplained 10%+ performance boost from simply adding a method argument (slimmer jit code)

[亡魂溺海] 提交于 2021-02-17 19:07:25
问题 (note: proper answer must go beyond reproduction). After millions of invocations, quicksort1 is definitely faster than quicksort2, which have identical code aside from this 1 extra arg. The code is at the end of the post. Spoiler: I also found the jit code is fatter by 224 bytes even if it should be actually simpler (like the byte code size tells; see very last update below). Even after trying to factor out this effect with some microbenchmark harness (JMH), the performance difference is

unexplained 10%+ performance boost from simply adding a method argument (slimmer jit code)

喜你入骨 提交于 2021-02-17 19:07:14
问题 (note: proper answer must go beyond reproduction). After millions of invocations, quicksort1 is definitely faster than quicksort2, which have identical code aside from this 1 extra arg. The code is at the end of the post. Spoiler: I also found the jit code is fatter by 224 bytes even if it should be actually simpler (like the byte code size tells; see very last update below). Even after trying to factor out this effect with some microbenchmark harness (JMH), the performance difference is

How to Decompile Bytenode “jsc” files?

余生长醉 提交于 2021-02-16 16:34:05
问题 I've just seen this library ByteNode it's the same as ByteCode of java but this is for NodeJS. This library compiles your JavaScript code into V8 bytecode, which protect your source code, I'm wondering is there anyway to Decompile byteNode therefore it's not secure enough. I'm wondering because I would like to protect my source code using this library? 回答1: TL;DR It'll raise the bar to someone copying the code and trying to pass it off as their own. It won't prevent a dedicated person from