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

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.