"Hello World" no_std linker error

help
1

Hi,

I've been trying to get this "Hello World" to build under the latest stable (1.46.0), and it won't work.

I copied the source from the linked post and get the following error:

error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-m64" "-Wl,--eh-frame-hdr" "-L" "/home/ambiso/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "/home/ambiso/Documents/Projects/echo/target/debug/deps/echo-8931c6e21c0c4d8a.4gijvs203q71b4l8.rcgu.o" "/home/ambiso/Documents/Projects/echo/target/debug/deps/echo-8931c6e21c0c4d8a.r3qi88wqf9d15wl.rcgu.o" "-o" "/home/ambiso/Documents/Projects/echo/target/debug/deps/echo-8931c6e21c0c4d8a" "-Wl,--gc-sections" "-pie" "-Wl,-zrelro" "-Wl,-znow" "-nodefaultlibs" "-L" "/home/ambiso/Documents/Projects/echo/target/debug/deps" "-L" "/home/ambiso/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" "/home/ambiso/Documents/Projects/echo/target/debug/deps/liblibc-fe6f0c4fc5d79e24.rlib" "/home/ambiso/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_std_workspace_core-cbfb51de52131460.rlib" "/home/ambiso/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-97497c26fddb7882.rlib" "/home/ambiso/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-f1a9d8c443e20b5e.rlib" "-Wl,-Bdynamic" "-lutil" "-ldl" "-lutil"
  = note: /usr/bin/ld: /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../lib/Scrt1.o: in function `_start':
          (.text+0x16): undefined reference to `__libc_csu_fini'
          /usr/bin/ld: (.text+0x1d): undefined reference to `__libc_csu_init'
          /usr/bin/ld: (.text+0x2a): undefined reference to `__libc_start_main'
          /usr/bin/ld: /home/ambiso/Documents/Projects/echo/target/debug/deps/echo-8931c6e21c0c4d8a.4gijvs203q71b4l8.rcgu.o: in function `main':
          /home/ambiso/Documents/Projects/echo/src/main.rs:11: undefined reference to `printf'
          collect2: error: ld returned 1 exit status


error: aborting due to previous error

Here's the main.rs I'm using:

#![no_std]
#![no_main]

extern crate libc;

#[no_mangle]
pub extern "C" fn main(_argc: isize, _argv: *const *const u8) -> isize {
    // Since we are passing a C string the final null character is mandatory
    const HELLO: &'static str = "Hello, world!\n\0";
    unsafe {
        libc::printf(HELLO.as_ptr() as *const _);
    }
    0
}

#[panic_handler]
fn my_panic(_info: &core::panic::PanicInfo) -> ! {
    loop {}
}

Here is my Cargo.toml:

[package]
name = "echo"
version = "0.1.0"
authors = ["ambiso <ambiso@invalid>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

libc = { version = "*", features = [] }

[profile.dev]
panic = 'abort'

[profile.release]
# opt-level = 'z'  # Optimize for size.
# lto = true
# codegen-units = 1
panic = 'abort'

I've found this related issue but I couldn't make it work.

Thanks for any help!

2

Try deleting the target folder.

3

Unfortunately that did not help, I get the exact same error.

4

I've fixed it by adding -lc to the rustc command.
This can also be achieved by adding the following file in .cargo/config

[build]
rustflags = ["-C", "link-args=-lc"]

I'm not sure why seemingly nobody has encountered this error before.
Why isn't rust linking with libc by itself?

5

It only links libc when it is told to do so. Normally this is done by the libc crate used as dependency of libstd.

6

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