bytecode

问题 My professor recently said that although x = x + 1 and x++ will obviously give the same result, there is a difference in how they are implemented in the JVM. What does it mean? Isn't compiler like: hey, I see x++ so I will switch it to x = x + 1 and carry on? I doubt there is any difference when it comes to efficiency, but I would be surprised if assembly would be different in those cases... 回答1: My professor recently said that although x = x + 1 and x++ will obviously give the same result I

问题 My professor recently said that although x = x + 1 and x++ will obviously give the same result, there is a difference in how they are implemented in the JVM. What does it mean? Isn't compiler like: hey, I see x++ so I will switch it to x = x + 1 and carry on? I doubt there is any difference when it comes to efficiency, but I would be surprised if assembly would be different in those cases... 回答1: My professor recently said that although x = x + 1 and x++ will obviously give the same result I

问题 To what extent is python bytecode compatible between releases. I'm not talking about python2.x to python3.x but say... Python33 to python34? I am not after it for 'security' I use Cython to convert the bulk of a program to C, I do however use pyc file as a means to store some constants and pyc is preferable as it provides a file format that isn't easily changed unofficially. If someone wants something changed they can request via internal procedures Such a pyc file only contains variables

问题 Is it possible to change strings (content and size) in Lua bytecode so that it will still be correct? It's about translating strings in Lua bytecode. Of course, not every language has the same size for each word... 回答1: Yes, it is if you know what you're doing. Strings are prefixed by their size stored as an int. The size and endianness of that int is platform-dependent. But why do you have to edit bytecode? Have you lost the sources? 回答2: After some diving throught Lua source-code I found

问题 This might be a silly question, but, given the output of, say.. >>> from dis import dis >>> def myfunc(x): ... print x ** 2 ... >>> dis(myfunc) 2 0 LOAD_FAST 0 (x) 3 LOAD_CONST 1 (2) 6 BINARY_POWER 7 PRINT_ITEM 8 PRINT_NEWLINE 9 LOAD_CONST 0 (None) 12 RETURN_VALUE ..or a .pyc file - is it possible to reassembling this into a valid piece of Python source code? I.e where reassemble(dis(myfunc)) == "def reassembled_function(x):\n print x ** 2" Not for any particular practical reason, I'm just

问题 Following Scala mailing lists, different people often say: "compiler rewrites this [scala] code into this [java/scala??] code". For example, from one of the latest threads, if Scala sees class C(i: Int = 4) { ... } then the compiler rewrites this as (effectively): class C(i: Int) { ... } object C { def init$default$1: Int = 4 } How can I find out, what will be the compiler output for my code? Should I decompile the resulting bytecode for that? 回答1: You can use "-print" as compiler option, and

问题 What could help me in helping writing highly compact(least byte code count) programs in Java. Possibly I'm looking at: A tool that tells me how many byte codes a Class or a method generates. To visualize byte codes. The tool could tell me which areas need optimization in terms of byte code count or cpu cycles. A byte code chart would also help indicating what byte codes exist in Java and its various properties. Any existing tools that would help me to realize this? 回答1: Eclipse has a Byte

问题 Based on Brett Walker's comment to this question, I was wondering how it can be done. "If you want to fail the unit test, in the most general sense, when ever a catch clause is executed by the code in this method you are going to have to instrument the byte code to tell you when a catch clause is being executed. This is a complex task. I would not recommend this." How would I test that some method has executed a catch clause? (the isCatched() in the example below. Let's say I have the

问题 This question already has answers here : How to get all imports defined in a class using java reflection? (3 answers) Closed 2 years ago . Is there a way to find out what imports a class has? In this question: Jon Skeet says that you can't do this using reflection, but If you want to find all the types used within the compiled code, that's a slightly different matter. You may want to look at BCEL as a way of analyzing bytecode. This is what I want to know how to do. 回答1: Here is an old

问题 I would like to translate a plain Three Address Code file to Java Bytecode. There are some questions related to this topic already, but either they are not answered properly or the question goes way beyond what I'm looking for. Take for instance this segment of code, generated with the front end of the compiler available in the "Dragon Book": L1:L3: i = i + 1 L5: t1 = i * 8 t2 = a [ t1 ] if t2 < v goto L3 L4: j = j - 1 How would it look like in bytecode? Do I need to reconstruct the symbol