bytecode | Python module to modify bytecode | Bytecode library
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kandi X-RAY | bytecode Summary
Python module to modify bytecode
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Currently covering the most popular Java, JavaScript and Python libraries. See a Sample of bytecode
bytecode Key Features
bytecode Examples and Code Snippets
public static int[] convertToByteCode(String instructions) {
if (instructions == null || instructions.trim().length() == 0) {
return new int[0];
}
var splitedInstructions = instructions.trim().split(" ");
var bytecode = new int
public static String toBinary(String bytecode) {
return bytecode.replaceFirst("^0x", "");
}
Community Discussions
Trending Discussions on bytecode
QUESTION
I've created a new Java project in IntelliJ with Gradle that uses Java 17. When running my app it has the error Cause: error: invalid source release: 17
.
My Settings
I've installed openjdk-17
through IntelliJ
and set it as my Project SDK
.
The Project language level
has been set to 17 - Sealed types, always-strict floating-point semantics
.
In Modules -> Sources
I've set the Language level
to Project default (17 - Sealed types, always strict floating-point semantics)
.
In Modules -> Dependencies
I've set the Module SDK
to Project SDK openjdk-17
.
In Settings -> Build, Execution, Deployment -> Compiler -> Java Compiler
I've set the Project bytecode version
to 17
.
Gradle
...ANSWER
Answered 2021-Oct-24 at 14:23The message typically entails that your JAVA_HOME environment variable points to a different Java version.
Here are the steps to follow:
- Close IntelliJ IDEA
- Open a terminal window and check your JAVA_HOME variable value:
- *nix system:
echo $JAVA_HOME
- Windows system:
echo %JAVA_HOME%
- *nix system:
- The JAVA_HOME path should be pointing to a different path, then set it to the openjdk-17 path:
- *nix system:
export JAVA_HOME=/path/to/openjdk-17
- Windows system:
set JAVA_HOME=path\to\openjdk-17
- *nix system:
- Open your project again in IntelliJ IDEA
- Make sure to set both source and target compatibility versions (not only the
sourceCompatibility
)
You should be able to build your project.
EDIT: Gradle ToolchainYou may need also to instruct Gradle to use a different JVM than the one it uses itself by setting the Java plugin toolchain to your target version:
QUESTION
I am trying to deploy my SimpleStorage.sol contract to a ganache local chain by making a transaction using python. It seems to have trouble connecting to the chain.
...ANSWER
Answered 2022-Jan-17 at 18:17Had this issue myself, apparently it's some sort of Ganache CLI error but the simplest fix I could find was to change the network id in Ganache through settings>server to 1337. It restarts the session so you'd then need to change the address and private key variable.
If it's the same tutorial I'm doing, you're likely to come unstuck after this... the code for transaction should be:
QUESTION
I am trying to compile and load dynamically generated Java code during runtime. Since both ClassLoader::defineClass and Unsafe::defineAnonymousClass have serious drawbacks in this scenario, I tried using hidden classes via Lookup::defineHiddenClass instead. This works fine for all classes that I tried to load, except for those that call lambda expressions or contain anonymous classes.
Calling a lambda expression throws the following exception:
...ANSWER
Answered 2022-Feb-23 at 18:19You can not turn arbitrary classes into hidden classes.
The documentation of defineHiddenClass
contains the sentence
- On any attempt to resolve the entry in the run-time constant pool indicated by
this_class
, the symbolic reference is considered to be resolved toC
and resolution always succeeds immediately.
What it doesn’t spell out explicitly is that this is the only place where a type resolution ever ends up at the hidden class.
But it has been said unambiguously in bug report JDK-8222730:
For a hidden class, its specified hidden name should only be accessible through the hidden class's 'this_class' constant pool entry.
The class should not be accessible by specifying its original name in, for example, a method or field signature even within the hidden class.
Which we can check. Even a simple case like
QUESTION
So I lately came across an explanation for Python's interpreter and compiler (CPython specifically).
Please correct me if I'm wrong. I just want to be sure I understand these specific concepts.
So CPython gets both compiled (to bytecode) and then interpreted (in the PVM)? And what does the PVM do exactly? Does it read the bytecode line by line, and translate each one to binary instructions that can be executed on a specific computer? Does this mean that a computer based on an Intel processor needs a different PVM from an AMD-based computer?
...ANSWER
Answered 2022-Feb-09 at 13:49- Yes, CPython is compiled to bytecode which is then executed by the virtual machine.
- The virtual machine executes instructions one-by-one. It's written in C (but you can write it in another language) and looks like a huge
if/else
statement like "if the current instruction is this, do this; if the instruction is this, do another thing", and so on. Instructions aren't translated to binary - that's why it's called an interpreter.- You can find the list of instructions here: https://docs.python.org/3.10/library/dis.html#python-bytecode-instructions
- The implementation of the VM is available here: https://github.com/python/cpython/blob/f71a69aa9209cf67cc1060051b147d6afa379bba/Python/ceval.c#L1718
- Bytecode doesn't have a concept of "line": it's just a stream of bytes. The interpreter can read one byte at a time and use another
if/else
statement to decide what instruction it's looking at. For example:
QUESTION
So I'm currently trying to deploy a router smart contract. I've been building it through erdpy contract build
, which has been successful (I'm on rust nightly tool chain as the Smart contract needs it). And I am now trying to deploy it, but I can't manage to do it. I keep having a 400 BadRequest
from https://devnet-api.elrond.com/transaction/send
.
Here are the logs from the deployment:
...ANSWER
Answered 2022-Jan-05 at 10:47I have you tried to deploy with the argument --verbose
?
That should be something like that (not sure of the syntax because I am on phone)
erdpy --verbose contract deploy
QUESTION
was looking at this V8 design doc where it has a section for Constant Pool Entries
it says
Constant pools are used to store heap objects and small integers that are referenced as constants in generated bytecode. and
... Small integers and the strong referenced oddball type’s have bytecodes to load them directly and do not go into the constant pool.
So I am confused: are small integers pooled or not?
My understanding is that it is not worth it pooling small integers if sizeof(int) < sizeof(int *)
- because it is cheaper to just copy the actual integer instead of copying the pointer that points to the integer in the constant pool. Also variables that hold integers can be optimised to be stored directly in CPU registers and skip being allocated in memory first.
Also, are they located on the V8 heap or the stack? My understanding had always been that smis are just be the immediate values allocated on the stack instead of being a pointer + an integer allocated on heap. Also if you take a heap snapshot using chrome devtool you cannot find smis in the heap snapshot - only heap number such as big integers or double like 3.14 are on the heap until I saw this article https://v8.dev/blog/pointer-compression#value-tagging-in-v8
JavaScript values in V8 are represented as objects and allocated on the V8 heap, no matter if they are objects, arrays, numbers or strings. This allows us to represent any value as a pointer to an object.
Now I am just baffled - are smis also allocated on the heap?
...ANSWER
Answered 2022-Jan-17 at 12:37V8 developer here.
are small integers pooled or not?
They are not (at least not right now). That said, this is a small implementation detail and could be done either way: it would totally be possible to use the constant pool for Smis. I suppose the decision to build special machinery for Smis (instead of reusing the general-purpose constant pool) was made because things turned out to be more efficient that way.
it is not worth it pooling small integers if
sizeof(int) < sizeof(int *)
The details are different (a Smi is not an int
, and constant pool slots are referenced by index rather than C++ pointer), but this reasoning does go in the right direction: avoiding indirections can save time and memory.
are smis also allocated on the heap?
Yes, everything is allocated on the heap. The stack is only useful for temporary (and sufficiently small) things; that's largely unrelated to the type of thing.
The "trick" of Smis is that they're not stored as separate objects: when you have an object that refers to a Smi, such as let foo = {smi: 42}
, then the value 42
can be smi-encoded and stored directly inside the "foo" object (whereas if the value was 42.5
, then the object would store a pointer to a separate "HeapNumber"). But since the object is on the heap, so is the Smi.
@DanielCruz
What I understand [...] is that constant small integers are pooled. Variable small integers are not.
Nope. Any literal that occurs in source code is "constant". Whether you use let
or const
for your variables has nothing to do with this.
QUESTION
I have noticed different behavior when using env_parent()
from rlang
package and when using env_parent(caller_env())
, although caller_env()
is a default argument for env_parent()
first parameter:
ANSWER
Answered 2022-Jan-15 at 21:30The short answer to your question is, there is a difference between explicitly calling a function with an argument, compared to calling the function and letting it supply the same argument as default by itself. In the latter case, the caller environment is the execution environment of the function. In the former case the caller environment is where the function was explicitly called from.
It took me a while to find a nice visualization of what is going on, but I think I found one.
Let's create two functions similar to {rlang}'s env_parent
and caller_env
. The difference is that myCallEnv
will not only return the execution environment of the calling function, it will also show the call strack tree with lobstr::cst()
:
QUESTION
The JLS states, that for arrays, "The enhanced for statement is equivalent to a basic for statement of the form". However if I check the generated bytecode for JDK8, for both variants different bytecode is generated, and if I try to measure the performance, surprisingly, the enhanced one seems to be giving better results(on jdk8)... Can someone advise why it's that? I'd guess it's because of incorrect jmh testing, so if it's that, please suggest how to fix that. (I know that JMH states not to test using loops, but I don't think this applies here, as I'm actually trying to measure the loops here)
My JMH testing was rather simple (probably too simple), but I cannot explain the results. Testing JMH code is below, typical results are:
...ANSWER
Answered 2022-Jan-05 at 19:41TL;DR: You are observing what happens when JIT compiler cannot trust that values
are not changing inside the loop. Additionally, in the tiny benchmark like this, Blackhole.consume
costs dominate, obscuring the results.
Simplifying the test:
QUESTION
I ran the code in VSCode and got a TypeError: Object of type set is not JSON serializable
. I just start to learn to code, really don't get it, and googled it, also didn't know what does JSON serializable means.
ANSWER
Answered 2021-Dec-29 at 01:48Instead of this:
QUESTION
Just tried JDK17 on Eclipse 2021-09 to have it fail with a java.lang.VerifyError
, which wasn't very helpful itself. I tracked it down to a switch statement, that gets fed a value pulled out of a Map
or another generic type. If I use a local variable in the switch statement instead, everything works as intended.
Test code:
...ANSWER
Answered 2021-Oct-26 at 09:25It is a problem with your Eclipse, not with Java-17 itself. Java-17 has been released only yesterday. Wait for some time until the IDEs are updated to support Java-17.
Demo:
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Vulnerabilities
No vulnerabilities reported
Install bytecode
You can use bytecode like any standard Python library. You will need to make sure that you have a development environment consisting of a Python distribution including header files, a compiler, pip, and git installed. Make sure that your pip, setuptools, and wheel are up to date. When using pip it is generally recommended to install packages in a virtual environment to avoid changes to the system.
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