Build two binaries

.gitignore

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+/result*
+

app/.cargo/config.toml

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+[target.thumbv7m-none-eabi]
+# uncomment this to make `cargo run` execute programs on QEMU
+# runner = "qemu-system-arm -cpu cortex-m3 -machine lm3s6965evb -nographic -semihosting-config enable=on,target=native -kernel"
+
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+# uncomment ONE of these three option to make `cargo run` start a GDB session
+# which option to pick depends on your system
+# runner = "arm-none-eabi-gdb -q -x openocd.gdb"
+# runner = "gdb-multiarch -q -x openocd.gdb"
+# runner = "gdb -q -x openocd.gdb"
+
+rustflags = [
+  # This is needed if your flash or ram addresses are not aligned to 0x10000 in memory.x
+  # See https://github.com/rust-embedded/cortex-m-quickstart/pull/95
+  "-C", "link-arg=--nmagic",
+
+  # LLD (shipped with the Rust toolchain) is used as the default linker
+  "-C", "link-arg=-Tlink.x",
+
+  # if you run into problems with LLD switch to the GNU linker by commenting out
+  # this line
+  "-C", "linker=lld",
+
+  # if you need to link to pre-compiled C libraries provided by a C toolchain
+  # use GCC as the linker by commenting out both lines above and then
+  # uncommenting the three lines below
+  # "-C", "linker=arm-none-eabi-gcc",
+  # "-C", "link-arg=-Wl,-Tlink.x",
+  # "-C", "link-arg=-nostartfiles",
+]
+
+[build]
+# Pick ONE of these compilation targets
+# target = "thumbv6m-none-eabi"        # Cortex-M0 and Cortex-M0+
+target = "thumbv7m-none-eabi"        # Cortex-M3
+# target = "thumbv7em-none-eabi"       # Cortex-M4 and Cortex-M7 (no FPU)
+# target = "thumbv7em-none-eabihf"     # Cortex-M4F and Cortex-M7F (with FPU)
+# target = "thumbv8m.base-none-eabi"   # Cortex-M23
+# target = "thumbv8m.main-none-eabi"   # Cortex-M33 (no FPU)
+# target = "thumbv8m.main-none-eabihf" # Cortex-M33 (with FPU)

app/.gitignore

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+**/*.rs.bk
+.#*
+.gdb_history
+target/
+
+# editor files
+.vscode/*
+!.vscode/*.md
+!.vscode/*.svd
+!.vscode/launch.json
+!.vscode/tasks.json
+!.vscode/extensions.json

app/Cargo.toml

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+[package]
+authors = ["Alex Martens <[email protected]>"]
+edition = "2018"
+readme = "README.md"
+name = "app"
+version = "0.1.0"
+
+[dependencies]
+cortex-m = "0.7"
+cortex-m-rt = "0.7"
+cortex-m-semihosting = "0.5.0"
+panic-halt = "0.2.0"
+
+# Uncomment for the panic example.
+# panic-itm = "0.4.1"
+
+# Uncomment for the allocator example.
+# alloc-cortex-m = "0.4.0"
+
+# Uncomment for the device example.
+# Update `memory.x`, set target to `thumbv7em-none-eabihf` in `.cargo/config`,
+# and then use `cargo build --examples device` to build it.
+# [dependencies.stm32f3]
+# features = ["stm32f303", "rt"]
+# version = "0.7.1"
+
+# this lets you use `cargo fix`!
+[[bin]]
+name = "app"
+test = false
+bench = false
+
+[profile.release]
+codegen-units = 1 # better optimizations
+debug = true # symbols are nice and they don't increase the size on Flash
+lto = true # better optimizations

app/build.rs

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+//! This build script copies the `memory.x` file from the crate root into
+//! a directory where the linker can always find it at build time.
+//! For many projects this is optional, as the linker always searches the
+//! project root directory -- wherever `Cargo.toml` is. However, if you
+//! are using a workspace or have a more complicated build setup, this
+//! build script becomes required. Additionally, by requesting that
+//! Cargo re-run the build script whenever `memory.x` is changed,
+//! updating `memory.x` ensures a rebuild of the application with the
+//! new memory settings.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::PathBuf;
+
+fn main() {
+    // Put `memory.x` in our output directory and ensure it's
+    // on the linker search path.
+    let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    File::create(out.join("memory.x"))
+        .unwrap()
+        .write_all(include_bytes!("memory.x"))
+        .unwrap();
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // By default, Cargo will re-run a build script whenever
+    // any file in the project changes. By specifying `memory.x`
+    // here, we ensure the build script is only re-run when
+    // `memory.x` is changed.
+    println!("cargo:rerun-if-changed=memory.x");
+}

app/default.nix

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+{ lib
+, rustPlatform
+, lld
+}:
+
+let
+  cargoToml = builtins.fromTOML (builtins.readFile ./Cargo.toml);
+in
+rustPlatform.buildRustPackage {
+  inherit (cargoToml.package) version;
+  pname = cargoToml.package.name;
+
+  src = ./.;
+
+  cargoLock.lockFile = ./Cargo.lock;
+
+  nativeBuildInputs = [
+    lld
+  ];
+
+  # no tests for no_std
+  doCheck = false;
+}

app/examples/allocator.rs

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+//! How to use the heap and a dynamic memory allocator
+//!
+//! This example depends on the alloc-cortex-m crate so you'll have to add it to your Cargo.toml:
+//!
+//! ``` text
+//! # or edit the Cargo.toml file manually
+//! $ cargo add alloc-cortex-m
+//! ```
+//!
+//! ---
+
+#![feature(alloc_error_handler)]
+#![no_main]
+#![no_std]
+
+extern crate alloc;
+use panic_halt as _;
+
+use self::alloc::vec;
+use core::alloc::Layout;
+
+use alloc_cortex_m::CortexMHeap;
+use cortex_m::asm;
+use cortex_m_rt::entry;
+use cortex_m_semihosting::{hprintln, debug};
+
+// this is the allocator the application will use
+#[global_allocator]
+static ALLOCATOR: CortexMHeap = CortexMHeap::empty();
+
+const HEAP_SIZE: usize = 1024; // in bytes
+
+#[entry]
+fn main() -> ! {
+    // Initialize the allocator BEFORE you use it
+    unsafe { ALLOCATOR.init(cortex_m_rt::heap_start() as usize, HEAP_SIZE) }
+
+    // Growable array allocated on the heap
+    let xs = vec![0, 1, 2];
+
+    hprintln!("{:?}", xs).unwrap();
+
+    // exit QEMU
+    // NOTE do not run this on hardware; it can corrupt OpenOCD state
+    debug::exit(debug::EXIT_SUCCESS);
+
+    loop {}
+}
+
+// define what happens in an Out Of Memory (OOM) condition
+#[alloc_error_handler]
+fn alloc_error(_layout: Layout) -> ! {
+    asm::bkpt();
+
+    loop {}
+}