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khvzak
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Description

High level Lua 5.4/5.3/5.2/5.1 (including LuaJIT) bindings to Rust with async/await support

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mlua

Build Status Latest Version API Documentation

Guided Tour

mlua
is bindings to Lua programming language for Rust with a goal to provide safe (as far as it's possible), high level, easy to use, practical and flexible API.

Started as rlua v0.15 fork,

mlua
supports all major Lua versions (including LuaJIT) and allows to write native Lua modules in Rust as well as use Lua in a standalone mode.

mlua
supports the following Lua versions (and tested on Windows/macOS/Linux): - Lua 5.4 (
feature = "lua54"
) - Lua 5.3 (
feature = "lua53"
) - Lua 5.2 (
feature = "lua52"
) - Lua 5.1 (
feature = "lua51"
) - LuaJIT 2.1.0 beta (
feature = "luajit"
) - LuaJIT 2.0.5 stable (
feature = "luajit"
)

Additional

feature = "vendored"
enables building static Lua from sources during
mlua
compilation.

Usage

Async/await support

Starting from v0.3,

mlua
supports async/await for all Lua versions. This works using Lua coroutines and require running Thread along with enabling
feature = "async"
in
Cargo.toml
.

Examples: - HTTP Client - HTTP Client (json) - HTTP Server - TCP Server

Serialization (serde) support

With

serialize
feature flag enabled,
mlua
allows you to serialize/deserialize any type that implements
serde::Serialize
and
serde::Deserialize
into/from
mlua::Value
. In addition
mlua
provides
serde::Serialize
trait implementation for it (including user data support).

Example

Compiling

You have to enable one of the features

lua54
,
lua53
,
lua52
,
lua51
or
luajit
, according to the choosen Lua version.

By default

mlua
uses
pkg-config
tool to find lua includes and libraries for the chosen Lua version. In most cases it works as desired, although sometimes could be more preferable to use a custom lua library. To achieve this, mlua supports
LUA_INC
,
LUA_LIB
,
LUA_LIB_NAME
and
LUA_LINK
environment variables.
LUA_LINK
is optional and may be
dylib
(a dynamic library) or
static
(a static library,
.a
archive).

An example how to use them:

sh
my_project $ LUA_INC=$HOME/tmp/lua-5.2.4/src LUA_LIB=$HOME/tmp/lua-5.2.4/src LUA_LIB_NAME=lua LUA_LINK=static cargo build

mlua
also supports vendored lua/luajit using the auxilary crates lua-src and luajit-src. Just enable the
vendored
feature and cargo will automatically build and link specified lua/luajit version. This is the easiest way to get started with
mlua
.

Standalone mode

Add to

Cargo.toml
:
[dependencies]
mlua = { version = "0.5", features = ["lua53"] }

main.rs
use mlua::prelude::*;

fn main() -> LuaResult { let lua = Lua::new();

let map_table = lua.create_table()?;
map_table.set(1, "one")?;
map_table.set("two", 2)?;

lua.globals().set("map_table", map_table)?;

lua.load("for k,v in pairs(map_table) do print(k,v) end").exec()?;

Ok(())

}

Module mode

Example

Add to

Cargo.toml
:
[lib]
crate-type = ["cdylib"]

[dependencies] mlua = { version = "0.5", features = ["lua53", "module"] }

lib.rs
:
use mlua::prelude::*;

fn hello(_: &Lua, name: String) -> LuaResult { println!("hello, {}!", name); Ok(()) }

#[mlua::lua_module] fn my_module(lua: &Lua) -> LuaResult { let exports = lua.create_table()?; exports.set("hello", lua.create_function(hello)?)?; Ok(exports) }

And then (macOS example):

$ cargo rustc -- -C link-arg=-undefined -C link-arg=dynamic_lookup
$ ln -s ./target/debug/libmy_module.dylib ./my_module.so
$ lua5.3 -e 'require("my_module").hello("world")'
hello, world!

On macOS, you need to set additional linker arguments. One option is to compile with

cargo rustc --release -- -C link-arg=-undefined -C link-arg=dynamic_lookup
, the other is to create a
.cargo/config
with the following content: ``` toml [target.x8664-apple-darwin] rustflags = [ "-C", "link-arg=-undefined", "-C", "link-arg=dynamiclookup", ]

[target.aarch64-apple-darwin] rustflags = [ "-C", "link-arg=-undefined", "-C", "link-arg=dynamic_lookup", ] ``

On Linux you can build modules normally with
cargo build --release`. Vendored and non-vendored builds are supported for these OS.

On Windows

vendored
mode for modules is not supported since you need to link to a Lua dll. Easiest way is to use either MinGW64 (as part of MSYS2 package) with
pkg-config
or MSVC with
LUA_INC
/
LUA_LIB
/
LUA_LIB_NAME
environment variables.

More details about compiling and linking Lua modules can be found on the Building Modules page.

Safety

One of the

mlua
goals is to provide safe API between Rust and Lua. Every place where the Lua C API may trigger an error longjmp in any way is protected by
lua_pcall
, and the user of the library is protected from directly interacting with unsafe things like the Lua stack, and there is overhead associated with this safety.

Unfortunately,

mlua
does not provide absolute safety even without using
unsafe
. This library contains a huge amount of unsafe code. There are almost certainly bugs still lurking in this library! It is surprisingly, fiendishly difficult to use the Lua C API without the potential for unsafety.

Panic handling

mlua
wraps panics that are generated inside Rust callbacks in a regular Lua error. Panics could be resumed then by propagating the Lua error to Rust code.

For example: ``` rust let lua = Lua::new(); let f = lua.createfunction(|, ()| -> LuaResult<()> { panic!("test panic"); })?; lua.globals().set("rust_func", f)?;

let _ = lua.load(r#" local status, err = pcall(rust_func) print(err) -- prints: test panic error(err) -- propagate panic "#).exec();

unreachable!() ```

mlua
should also be panic safe in another way as well, which is that any
Lua
instances or handles remains usable after a user generated panic, and such panics should not break internal invariants or leak Lua stack space. This is mostly important to safely use
mlua
types in Drop impls, as you should not be using panics for general error handling.

Below is a list of

mlua
behaviors that should be considered a bug. If you encounter them, a bug report would be very welcome:
  • If your program panics with a message that contains the string "mlua internal error", this is a bug.

  • The above is true even for the internal panic about running out of stack space! There are a few ways to generate normal script errors by running out of stack, but if you encounter a panic based on running out of stack, this is a bug.

  • Lua C API errors are handled by lonjmp. All instances where the Lua C API would otherwise longjmp over calling stack frames should be guarded against, except in internal callbacks where this is intentional. If you detect that

    mlua
    is triggering a longjmp over your Rust stack frames, this is a bug!
  • If you detect that, after catching a panic or during a Drop triggered from a panic, a

    Lua
    or handle method is triggering other bugs or there is a Lua stack space leak, this is a bug.
    mlua
    instances are supposed to remain fully usable in the face of user generated panics. This guarantee does not extend to panics marked with "mlua internal error" simply because that is already indicative of a separate bug.

License

This project is licensed under the MIT license

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