Duktape
sol2
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Duktape | sol2 | |
---|---|---|
10 | 20 | |
5,830 | 3,927 | |
- | - | |
6.4 | 3.9 | |
28 days ago | 28 days ago | |
JavaScript | C++ | |
MIT License | MIT License |
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For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.
Duktape
- Roll your own JavaScript runtime, pt. 3
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How to Create a Modern C Project with CMake and Conan
Im my projects I search for single file libs.(like https://github.com/svaarala/duktape etc...)
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Is there anyway to bypass the limit of rand()?
Use lrand48(), or better, implement a high-quality RNG like PCG or splitmix64.
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Libgrapheme: A simple freestanding C99 library for Unicode
You can also refer to the Unicode routines of other small JS engines[1,2], those don’t use ICU either, although the implementations are mercilessly size-optimized (to put it politely) and restricted to what the target JS version requires (e.g. casemapping but no normalization).
[1] https://github.com/bellard/quickjs/blob/master/libunicode.c
[2] https://github.com/svaarala/duktape/blob/master/src-input/du...
- Duktape
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Nan Boxing
> memcpy from bytes to a NaN should work fine
Signaling NaNs are explicitly undefined in C11 F.2.1.: "This specification does not define the behavior of signaling NaNs." - and in practice may be "quieted" by conversion to Quiet NaNs, changing their bit patterns. Fast math optimization flags will also break the hell out of your code by assuming NaNs are impossible. I want to say there are more circumstances where optimizers and compiler generated code can butcher your NaN payloads, but I'd be working off recollected hearsay and I can't find a source, so don't quote me on that.
NaN boxing is common enough that, if you take the right precautions, a modern compiler should probably support it, maybe. NaN boxing is uncommon enough that, if your codebase needs to be sufficiently portable, you need an opt out for when it breaks. Let's review duktape's scars:
https://github.com/svaarala/duktape/blob/123d9426d5e5b36d5da...
https://github.com/svaarala/duktape/blob/5252b7a50611a3cb8bf...
https://github.com/svaarala/duktape/blob/224a0b89ca08a36e37e...
Note that "the right precautions" involve unions and proper integer types to avoid optimizer-invoked rewrites of the value and debugging when things go wrong, not simply YOLOing bytes into a double via memcpy. Note that debugging when it all goes terribly wrong can be quite painful. I've personally had the misfortune of being forced to debug duktape being built with fast math optimizatoins enabled on one "rare" platform + build configuration that wasn't caught by duktape's #if defined(__FAST_MATH__) checks linked above (wasn't Clang nor GCC, so go figure it didn't make the same #define)
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YouTube-dl has a JavaScript interpreter written in 870 lines of Python
I was expecting this to be about Duktape <https://github.com/svaarala/duktape>, but heh, for sure no. I'd bet $1 there's no way youtube-dl would switch, but I wonder if yt-dlp would?
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Optimizations Enabled by -ffast-Math
Fast math optimizations can break code like this by breaking isNaN.
I was porting a C++ project to a certain platform - and that platform enabled a -ffast-math equivalent by default in Release (but not Debug) builds! This broke duktape, a JS engine said project embedded, in some nasty and subtle ways. Instead of storing a number/pointer/??? (8 bytes) + type tag (4? bytes) for each dynamically typed JS value, duktape can bit-pack values into a single 8 byte "double" value by storing object/string handles as NaN values - this isn't an uncommon trick for dynamically typed scripting stuff:
https://github.com/svaarala/duktape/blob/c3722054ea4a4e50f48...
Naturally, the -ffast-math equivalent broke isNaN checks, which caused random object/string handles to be mistakenly reinterpreted as "numbers" - but only in Release builds, for this one particular platform, in one rarely taken branch, so neither QA nor CI caught it, leading to hours of manufacturing a repro case, stepping through an absurd amount of code, and then finally looking at the default build rules and facepalming.
Cursing the platform vendor under my breath, I overrode the defaults to align with the defaults of every other config x platform combination we already had: no fast math. If you want those optimizations, use SSE-friendly NaN-avoiding intrinsics - or, if you must use the compiler flags, ensure you do so consistently across build configs and platforms, perhaps limited to a few TUs or modules if possible. This allows you to have a chance at using your Debug builds to debug the resulting "optimizations".
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Can C++ and JS be used together?
Sure. For example, DukTape is an implementation of Javascript designed to be embedded in other projects. Google's V8 Javascript engine (used in Chrome), can also be embedded, see Node.Js for example.
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[AskJS] Do you use JavaScript on Microcontrollers? Which engine / interpreter?
- Duktape (4.8k stars)
sol2
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Any tips for how to make moddable games?
As someone said, make the game data-driven is a good first step but I will say, also have some sort of way to add additional game logic. For C++ games, lua is really easy to embed the interpreter in your C++ binary, read in the files from a directory (like /mods) with the C++ filesystem api new in C++17, and it's very easy to use SoL to write an API for lua specific to your game. Many games use lua in this way and it's probably the most common mod path setup.
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Script Interoperability
I've only ever done this from C++, but it's using the same lua C library, so should be durable from C as well. You can look up how sol2 or any other wrapper libraries do it.
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Need help trying to embed lua in c++
Consider sol2
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CBN Changelog: December 3, 2022. Improved LUA support in progress!
This version relies on a Lua C++ wrapper called sol2 to hide Lua stack management from the developer, so creating new bindings can be done by adding a few lines of human-readable C++. It still has to be done manually, but at least sol2 is able to automatically figure out types of objects being bound, so it's not much different from our de-/serialization code.
- RTS programming game where you write real C++ code to control your player.
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why?
Here's an example: sol2
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Tools for rolling your own engine
Here is link number 2 - Previous text "Sol"
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Storing pointers to C++ data in Lua in a type-safe-ish manner that are comparable on the Lua side.
Have you considered using sol2? https://github.com/ThePhD/sol2 Or if you don't want to switch over, you can at least look at their code and see how they handle this.
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jluna: a new Julia <-> C++ Wrapper
It is half of a pun as I was inspired by [sol3](https://github.com/ThePhD/sol2) which is a lua <-> c++ wrapper. Sol means sun and the julia c-api prefixes all it's functions with jl, luna means moon so it is pronounced "jay luna"
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A new C++ <-> Julia Wrapper: jluna
If you want to be portable I'd recommend C++ and Lua, I used those for years and it runs on everything and there's this most amazing wrapper API which was a huge inspiration
What are some alternatives?
V8 - The official mirror of the V8 Git repository
Lua - Lua is a powerful, efficient, lightweight, embeddable scripting language. It supports procedural programming, object-oriented programming, functional programming, data-driven programming, and data description.
quickjs - Public repository of the QuickJS Javascript Engine.
pybind11 - Seamless operability between C++11 and Python
ChaiScript - Embedded Scripting Language Designed for C++
jerryscript - Ultra-lightweight JavaScript engine for the Internet of Things.
SWIG - SWIG is a software development tool that connects programs written in C and C++ with a variety of high-level programming languages.
Wren - The Wren Programming Language. Wren is a small, fast, class-based concurrent scripting language.