no-std Build

The feature no_std automatically converts the scripting engine into a no-std build.

Usually, a no-std build goes hand-in-hand with minimal builds because typical embedded hardware (the primary target for no-std) has limited storage.

Nightly Required

Currently, no_std requires the nightly compiler due to the crates that it uses.


Rhai allocates, so the first thing that must be included in any no-std project is an allocator crate, such as wee_alloc.

Then there is the need to set up proper error/panic handlers. The following example uses panic = "abort" and wee_alloc as the allocator.

// Set up for no-std.

// The following no-std features are usually needed.
#![feature(alloc_error_handler, start, core_intrinsics, lang_items, link_cfg)]

// Set up the global allocator.
extern crate alloc;
extern crate wee_alloc;

static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;

// Rust needs a CRT runtime on Windows when compiled with MSVC.
#[cfg(all(windows, target_env = "msvc"))]
#[link(name = "msvcrt")]
#[link(name = "libcmt")]
extern {}

// Set up panic and error handlers
fn err_handler(_: core::alloc::Layout) -> ! {

#[lang = "panic_impl"]
extern "C" fn rust_begin_panic(_: &core::panic::PanicInfo) -> ! {

#[lang = "eh_personality"]
extern "C" fn eh_personality() {}

extern "C" fn rust_eh_register_frames() {}

extern "C" fn rust_eh_unregister_frames() {}

fn main(_argc: isize, _argv: *const *const u8) -> isize {
    // ... main program ...


Check out the no-std sample applications for different operating environments.


Currently, the SmartString crate used by Rhai does not properly handle no-std builds.

Therefore, it is necessary to patch this crate until the issue is fixed.

# Patch smartstring wth a PR fix because it doesn't properly handle no-std builds.
smartstring = { git = "" }