According to xargo my code has built successfully, but there's no binary in target, why?

Question

I'm brand new to Rust so forgive me if I don't know the lingo/tools yet. I'm trying to get an STM32F4 to blink an LED, and I think the code is right, but when I build it xargo doesn't generate a binary or any sort of error. My code is:

#![feature(proc_macro)] // <- IMPORTANT! Feature gate for procedural macros
#![no_std]

extern crate cortex_m;
extern crate cortex_m_rtfm as rtfm;
extern crate stm32f40x;

use cortex_m::peripheral::SystClkSource;
use rtfm::{app, Threshold};

app! {
    device: stm32f40x,
    resources: {},
    tasks: {
        SYS_TICK: {
            path: toggle,
            resources: [GPIOC],
        },
    },
}

fn init(p: init::Peripherals, _r: init::Resources) {
    // TODO: initialize the GPIO
    p.SYST.set_clock_source(SystClkSource::Core);
    p.SYST.set_reload(8_000_000); // 1s?
    p.SYST.enable_interrupt();
    p.SYST.enable_counter();
}

fn idle() -> ! {
    loop {
        rtfm::wfi();
    }
}

fn toggle(_t: &mut Threshold, r: SYS_TICK::Resources) {
    **r.GPIOC.odr.modify(|r, w| w.odr13().bit(!r.odr13().bit()));
}

The Cargo.toml file is

[package]
name = "sign_firmware"
version = "0.0.1"
authors = ["teryret"]
categories = ["embedded", "no-std"]
description = "With any luck this will cause an STM32F4 based board to drive a few thousand LEDs."
keywords = ["arm", "cortex-m"]
license = "MIT OR Apache-2.0"
repository = "TODO"
[dependencies]
cortex-m = "*"
cortex-m-rt = "*"
cortex-m-rtfm = "*"
stm32f40x = "*"

[profile]
[profile.release]
debug = true
lto = true

[target.arm-none-linux-gnueabihf]
ar = "arm-linux-gnueabihf-gcc-ar"
linker = "arm-linux-gnueabihf-gcc"

And when I run xargo build --release in the docker image I set up to contain all the dependencies and whatnot it says:

teryret@bee ~/d/rtfm> ./build 
   Compiling core v0.0.0 (file:///usr/local/rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libcore)
    Finished release [optimized + debuginfo] target(s) in 12.82 secs
    Updating git repository `https://github.com/rust-lang-nursery/compiler-builtins`
   Compiling compiler_builtins v0.1.0 (https://github.com/rust-lang-nursery/compiler-builtins#f5532b22)
    Finished release [optimized + debuginfo] target(s) in 2.12 secs
warning: unused manifest key: target.arm-none-linux-gnueabihf.ar
warning: unused manifest key: target.arm-none-linux-gnueabihf.linker
 Downloading cortex-m-rtfm v0.2.1
 Downloading stm32f40x v0.5.0
 Downloading cortex-m-rt v0.3.6
 Downloading cortex-m v0.3.1
 Downloading rtfm-core v0.1.0
 Downloading static-ref v0.2.1
 Downloading cortex-m-rtfm-macros v0.2.0
 Downloading error-chain v0.10.0
 Downloading quote v0.3.15
 Downloading rtfm-syntax v0.1.0
 Downloading syn v0.11.11
 Downloading unicode-xid v0.0.4
 Downloading synom v0.11.3
 Downloading volatile-register v0.2.0
 Downloading bare-metal v0.1.1
 Downloading aligned v0.1.1
 Downloading vcell v0.1.0
 Downloading r0 v0.2.2
   Compiling r0 v0.2.2
   Compiling libc v0.2.33
   Compiling vcell v0.1.0
   Compiling quote v0.3.15
   Compiling cc v1.0.3
   Compiling sign_firmware v0.0.1 (file:///usr/src/myapp)
   Compiling cortex-m-rt v0.3.6
   Compiling cortex-m-rtfm v0.2.1
   Compiling cfg-if v0.1.2
   Compiling rustc-demangle v0.1.5
   Compiling bare-metal v0.1.1
   Compiling unicode-xid v0.0.4
   Compiling aligned v0.1.1
   Compiling cortex-m v0.3.1
   Compiling static-ref v0.2.1
   Compiling volatile-register v0.2.0
   Compiling synom v0.11.3
   Compiling rtfm-core v0.1.0
   Compiling syn v0.11.11
   Compiling stm32f40x v0.5.0
   Compiling backtrace-sys v0.1.16
   Compiling backtrace v0.3.4
   Compiling error-chain v0.10.0
   Compiling rtfm-syntax v0.1.0
   Compiling cortex-m-rtfm-macros v0.2.0
    Finished release [optimized + debuginfo] target(s) in 47.2 secs

While lots of stuff is generated in target/ none of it is a binary I can flash onto the board. Any idea why? I mean, it's got to be something simple, but I don't have the experience to know where to look.

Answer 1

In the tutorial you were following, all of the examples are in an "examples" directory. You can build these using the --example argument, as shown in the tutorial:

xargo build --example hello

If this is your primary program, however, you will want to put your code in "src/main.rs", allowing just:

xargo build

If you have multiple executables, you can also specify that.