Questions tagged [virtual-machine]
A virtual machine is an emulation layer between a program and the OS that presents to the application a specialized environment to run in, than the raw environment that the OS provides.
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Sandboxing interpreted code
I have a little pet compiler project that generates bytecode interpreted by a virtual machine. The language is kind of low-level, as it allows the user to manually allocate memory and dereference any ...
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Bytecode format and loading in language VMs
I am thinking about how to build a language VM. I have been able to get some of the basic constructs right, including jumps to functions within the chunk of bytecode that is currently loaded.
But now ...
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How to model opcodes effectively for a language VM?
I am learning about building a language VM with the long-term goal of writing an own language.
For guidance, I am looking at this LC3 tutorial by Justin Meiners and Building a Language VM by Fletcher ...
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How a VPS processes an incoming packet (conceptually)
I'm interested in understanding, conceptually (e.g., similar to how many of the concepts in networking are explained in textbooks like Tanenbaum's Computer Networks, or Kurose's Computer Networking), ...
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How should a bytecode VM call external C functions?
I am trying to implement a basic bytecode VM, which I plan to target with a compiler. How can I implement the ability to call external C functions using the bytecode, i.e., call arbitrary functions in ...
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VM-images: how protect time-license programs?
One big customer asked me to supply my program to run within a balanced VM-images structure; I mean, the program will be recorded into an image which will be launched in "instances" to ...
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Use of globals in stack-based virtual machine implementation
I'm implementing a stack-based virtual machine in C.
The following variables are used by pretty much every function:
memory array
various pointers to memory offsets
program counter
stack
stack ...
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Is there any reason I shouldn't use a LInux host for a Linux guest VM?
I'm a developer and my typical environment is to use is a Linux guest OS running inside VirtualBox on a Windows host. Most software companies don't allow developers to install Linux bare metal on ...
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What does it mean for an OS to compile down to a function?
I was reading the Urbit docs and stopped at this paragraph (emphasis mine):
The main thing to understand about our ‘overlay OS’, as we call it, is that the foundation is a single, simple function. ...
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How do language implementations implement native-extension class instantiation?
I'm writing a language interpreter in C. I'm currently implementing a system that allows writing extension modules in C for the interpreter.
These modules are loaded into a code file like a normal ...
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How do VMs and GCs treat objects which wrap yet active resources, but that are unreachable from user code?
I am building an interpreter in C for a simple programming language.
The interpreter is fitted with a built in garbage collector. The GC simply marks all objects which are linked from some root (the ...
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Why is it difficult to create a truly portable garbage collector for C?
When reading the Python docs for writing C extensions, one can find the following text in the part about CPython's garbage collection strategy (emphasis mine):
... The disadvantage [of automatic ...
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If my development machine is slow and has low end specifications, why can't I just rent a VM on Azure? [closed]
I need 16GB RAM on my development machine to do some Android programming but I can't really afford to buy a new one. So, what's there to stop me from just creating a VM on Azure, use it for just a few ...
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How can one bake a GUI framework inside an interpreter without freezing the interpreter?
I am writing a bytecode interpreter in C for a simple programming language.
I want to add GUI capabilities to the language. As a first step, I decided to bake into the interpreter a wrapper for the ...
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VNC security: SSH tunnel from local machine to VM necessary?
SETUP:
Local Windows 10 machine. It runs a VM (Ubuntu Server, NAT, Virtualbox)
QUESTION:
I want to make a VNC connection from my Local machine to the VM. Since VNC is not a secure protocol, it is ...
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To show the difference between system VMs and JVMs
I am trying to draw diagrams that show the difference between system virtual machines and Java virtual machines.
The first two images looks correct to me. But I don't know how to draw the third.
...
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How is an async stack implemented?
I am working on creating a simple VM sort of thing in JS:
let sp = 0 // stack pointer
let m = [] // memory
initialize:
sp = 0
invoke:
m[sp] = m[sp - 1] // position in stack
m[sp + 1] = input[m[...
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Is a call stack required for robust computer architecture?
I am not too familiar with the computer architecture terminology yet so please bear with me. I seem to understand that von Neumann architectures are more robust ("universal Turing machines") as ...
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Why do some VMs manage their own memory instead of relying fully on the system allocator?
As far as I know, most "serious" VM implementations, such as CPython and the Oracle JVM, do not request new memory from the operating system ("malloc()") each time they create a new object.
As far as ...
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How can I sync a git repository with directories from another machine?
My team and I use a git repository to keep track of our projects. This repository is cloned in our Windows PCs that we use to develop most of our software. However, we also use another machine ( a ...
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How are "registers" implemented in VMs?
Process VMs (such as the Oracle JVM, CPython, .NET CLR etc.) are usually stack-based or register-based.
Are the "registers" in a register-based VM actually the registers of the underlying physical ...
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OS tax in dockerized production environment
I am reading Docker deep dive since I am interested in this shiny technology.
I can read:
The VM model then carves low-level hardware resources into VMs. Each
VM is a software construct ...
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What is the best way to run untrusted hooks/plugins?
I'm building a data processing system where users can submit hooks to execute on incoming data.
The hooks are untrusted and should execute in a sandbox with access only to a limited API that I expose ...
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GCC or Clang to output bytecode for a VM?
Long story short, I wanted to use C as a scripting language and in a portable manner so I created a register-based, JITless VM to accomplish this.
I've formalized the VM's ISA, script file format, ...
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Why do we need nginx server on top of linux server?
Recently, I tried to deploy a web project to a virtual machine. I used the Ubuntu server as my OS, but while following along some tutorials I came to the fact which was very confusing for the beginner ...
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Why are most language virtual machines designed with a load/store architecture? Is there a speed advantage vs. a register-memory architecture?
I am developing a virtual machine for personal use (open source of course!)
In researching and looking at the source code of other virtual machines, especially those of scripting languages; I noted ...
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What is the minimum set of operations a language implementation must provide for it to be usable for all applications?
As a fun hobby project, I'm writing a simple bytecode VM and a compiler from a basic high-level language to the said bytecode.
(Offtopic: the compiler is inspired by Jack Crenshaw's awesome tutorial -...
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Is comparing "dollar-hours" for running a specific piece of code practical as an estimate of rented system performance?
Background: there'a a gazillion types of virtual machines in Microsoft Azure each having different performance and price. Such virtual machines are paid per hour. The goal is to decide how to get "the ...
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Sharing virtual box / environment?
I am wondering how do big development teams do it, when they all work on one project.
Options are:
1 virtual machine in cloud that they ssh into and push updates via ftp ?
each developer have ...
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Easy way to debug platform-specific issues of non-GUI software on Windows?
I'm maintaining a couple of software repositories (C, C++ essentially) which I want to also run - or let's start with at least build - seamlessly on Windows.
Now, my desktop machine does not have ...
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How can I access attached data section in custom script language?
Sorry if title is not clear, suggestions on better title are welcome.
For the purpose of [self-]education I am writing a toy scripting language that would compile to bytecode and be executed on a toy ...
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Help With Memory Mapped I/O and Hardware Interrupts for Virtual Machine
I've been working on a 24-bit virtual machine to help me learn more about computers and programming in general and was hoping to find a bit more information on memory mapped input/output and hardware ...
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How do interpreters and VM print?
While direct Language-Assembly compilers generate the code required to perform specific task for the given platform, how do interpreters do it?
Abstract example
The following pseudo-code...
printf(&...
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Are repeatable performance tests possible on a VM?
My application does a lot of database inserts, so disk I/O is a big part of the workload. QA does almost all testing on VM's. I'm concerned that tests intended to detect performance regressions won't ...
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Garbage collection virtual machine
Say you have a virtual machine with the following instruction set.
0 ACC <= [S] Copy address S from memory to ACC
1 ACC => [S] Copy the value of the ACC to the memory address S.
2 ...
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First time writing a scripting engine
So I decided to created a stack-based virtual machine and the result came out pretty good (in my opinion!). The first iteration was a basic toy VM.
I did a rewrite to make the VM work more ...
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safely executing arbitrary code
I have a program that can get code from a user as input (This question is language-agnostic, though I am primarily interested in answers for Java and Python). Usually, this code is going to be useful, ...
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Service dependencies during local development
I'm working on a system split into multiple services. Some services (and especially the front end web server) depend on other services to function. When developing these locally, do you point to the ...
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Criteria for a language (Terra as a tricky example) to be usable for operating system development, and how to meet missing criteria
For example, a language that I was looking at recently- Terra. You can address the question in the context of any language, I'm just most comfortable with Lua so I'm starting from there.
The Terra ...
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How exactly is bytecode "parsed"?
How is Bytecode "parsed"?
It is my understand that Bytecode is a binary, intermediate representation of the syntax of a given programming language. Certain programming languages convert their source ...
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How is memory modeled in projects like Apache Spark or Druid?
In the past couple of months I've worked with both Apache Spark and Druid for some projects. As I've gone through the process of learning how to use these tools, I've spent some time reading through ...
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What is a type system?
Background
I am designing a language, as a side project. I have a working assembler, static analyser, and virtual machine for it. Since I can already compile and run non-trivial programs using the ...
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Do bytecode compilers compile syntax directly or intermediate assembly language?
I am going to write a very simple VM and bytecode compiler. Is it typical for a bytecode compiler to read the syntax and attempt to create the bytecode directly or is there an intermediate stage to ...
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Using DB migration tools within a Virtual Machine with Vagrant
I am setting up Vagrant with multiple developers using ScotchBox (v2.5) in our workplace, I have got the initial vagrantfile working ok however I'm unsure of how best to handle Database migrations.
...
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How do Virtual Machines allocate memory?
If I want to allocate a struct in C,
#include<stdio.h>
typedef struct container {
int i;
} Container;
int main() {
Container *ptr_to_container;
ptr_to_container = (Container *) ...
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Testing a bootloader written from scratch?
I'm planning to write a simple bootloader. Nothing too complicated. Just really basic output and maybe keyboard input.
But it seems a bit crazy to restart my computer every time I want to run the ...
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One vagrant file (/var/www/VagrantFile) for multiple apps
I manage multiple apps in my dev:
/var/www/
qa
jt
auth
We have a QA vagrant which runs QA app in its own vagrant. My understanding was that each app would run its own VM but this would ...
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Computer Architectures NOT based on arrays [closed]
Wadler's original paper on Monads for Functional Programming ( Haskell ) ,he says
Another question with a long history is whether it is desirable to base programs on array update. Since so much ...
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What is the point of the Common Language Runtime (CLR)?
My understanding is that part of the point of the JVM was that the code could "run anywhere", but CLR code was designed to run only on Windows: so why have a virtual machine?
I know that the CLR ...
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New Kind of VM Type
I have designed my own kind of vm, a sort of stack-register. It works by having a stack but instead of pushing and popping values, you simply store the values on the stack, and add together different ...
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