How to build a Rust app free of shared libraries?

Question

How does one compile a Rust application without having to load shared libraries at all?

What have I tried:

ex.rs

fn main() {
  println!("Try to compile me statically!");
}

According to https://rust-lang.github.io/rfcs/1721-crt-static.html I performed the following:

$ rustc -C target-feature=+crt-static ./ex.rs
$ ldd ./ex
    linux-vdso.so.1 (0x00007ffc4e3ef000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fc30b8c4000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fc30b6bc000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fc30b49d000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fc30b285000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fc30ae94000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fc30bcfb000)

Why isn't libc compiled statically? And how to get rid of linking all other shared libraries?

Kheda

AFAIK standard libc (like glibc) aren't designed to be linked statically. You can try to use musl instead. – Ague

@Ague But my target project make use of the actix crate, which does not support musl. How to overcome it ? – Kheda

You fork actix or find an alternative – Freeforall

Answer 1

MUSL support for fully static binaries:
By default, Rust will statically link all Rust code. However, if you use the standard library, it will dynamically link to the system's libc implementation.

If you'd like a 100% static binary, the MUSL libc can be used on Linux:

rustup target add x86_64-unknown-linux-musl 

RUSTFLAGS='-C link-arg=-s' cargo build --release --target x86_64-unknown-linux-musl

main.rs file:

use actix_web::{web, App, HttpServer, Responder};

async fn index(info: web::Path<(String, u32)>) -> impl Responder {
    format!("Hello {}! id:{}", info.0, info.1)
}

#[actix_rt::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| App::new().service(web::resource("/{name}/{id}/index.html").to(index)))
        .bind("127.0.0.1:8080")?
        .run()
        .await
}

Cargo.toml file:

[profile.release]
opt-level = 's'  # Optimize for size.
lto = true # Link Time Optimization (LTO)
# codegen-units = 1 # Set this to 1 to allow for maximum size reduction optimizations:
# panic = 'abort' # removes the need for this extra unwinding code.

[dependencies]
actix-web = "2.0.0" # Actix web is a simple, pragmatic and extremely fast web framework for Rust.
actix-rt = "1.0.0"  # Actix runtime

Rust Platform Support

Brutalize

Thanks! It seems to be changed since the 2.0 version of actix. – Kheda