From 0d80be617c2cccc69216eeb286bd6f6e330b98e4 Mon Sep 17 00:00:00 2001
From: wcampbell <wcampbell1995@gmail.com>
Date: Tue, 8 Aug 2023 22:02:55 -0400
Subject: [PATCH] Change ensure_no_std to just build and thumbv7em-none-eabihf

---
 .github/workflows/main.yml    |  3 ++-
 ensure_no_std/Cargo.toml      |  3 ++-
 ensure_no_std/src/bin/main.rs | 40 +++++++++++++++++++++--------------
 src/impls/primitive.rs        |  2 ++
 src/impls/slice.rs            |  4 ++--
 5 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index ffb741f9..10ee0756 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -112,7 +112,8 @@ jobs:
         with:
           toolchain: nightly
           override: true
-      - run: cd ensure_no_std && cargo run --release
+          target: thumbv7em-none-eabihf
+      - run: cd ensure_no_std && cargo build --release --target thumbv7em-none-eabihf
 
   ensure_wasm:
     name: Ensure wasm
diff --git a/ensure_no_std/Cargo.toml b/ensure_no_std/Cargo.toml
index 5b9f659a..f3799d4a 100644
--- a/ensure_no_std/Cargo.toml
+++ b/ensure_no_std/Cargo.toml
@@ -19,6 +19,7 @@ default = ["alloc"]
 alloc = []
 
 [dependencies]
-wee_alloc = "0.4"
+cortex-m-rt = "0.7.3"
 deku = { path = "../", default-features = false, features = ["alloc"] }
+embedded-alloc = "0.5.0"
 
diff --git a/ensure_no_std/src/bin/main.rs b/ensure_no_std/src/bin/main.rs
index a64da7c8..954ddf17 100644
--- a/ensure_no_std/src/bin/main.rs
+++ b/ensure_no_std/src/bin/main.rs
@@ -1,25 +1,16 @@
-//! Based on https://github.com/rustwasm/wee_alloc/tree/master/example
-//! Run with `cargo +nightly run --release`
-
+//! cargo build --target thumbv7em-none-eabihf
 #![no_std]
 #![no_main]
-#![feature(core_intrinsics, alloc_error_handler)]
 
 extern crate alloc;
-extern crate wee_alloc;
 
-#[no_mangle]
-pub extern "C" fn _start() -> ! {
-    loop {}
-}
+use core::panic::PanicInfo;
 
-#[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
-    loop {}
-}
+use cortex_m_rt::entry;
+use embedded_alloc::Heap;
 
 #[global_allocator]
-static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
+static HEAP: Heap = Heap::empty();
 
 use alloc::{format, vec, vec::Vec};
 use deku::prelude::*;
@@ -35,8 +26,18 @@ struct DekuTest {
     data: Vec<u8>,
 }
 
-#[no_mangle]
-pub extern "C" fn main() -> () {
+#[entry]
+fn main() -> ! {
+    // Initialize the allocator BEFORE you use it
+    {
+        use core::mem::MaybeUninit;
+        const HEAP_SIZE: usize = 1024;
+        static mut HEAP_MEM: [MaybeUninit<u8>; HEAP_SIZE] = [MaybeUninit::uninit(); HEAP_SIZE];
+        unsafe { HEAP.init(HEAP_MEM.as_ptr() as usize, HEAP_SIZE) }
+    }
+
+    // now the allocator is ready types like Box, Vec can be used.
+
     let test_data: Vec<u8> = vec![0b10101_101, 0x02, 0xBE, 0xEF];
 
     // Test reading
@@ -54,4 +55,11 @@ pub extern "C" fn main() -> () {
     // Test writing
     let val = val.to_bytes().unwrap();
     assert_eq!(test_data, val);
+
+    loop { /* .. */ }
+}
+
+#[panic_handler]
+fn panic(_: &PanicInfo) -> ! {
+    loop {}
 }
diff --git a/src/impls/primitive.rs b/src/impls/primitive.rs
index 64927b32..dced374d 100644
--- a/src/impls/primitive.rs
+++ b/src/impls/primitive.rs
@@ -1,5 +1,7 @@
 #[cfg(feature = "alloc")]
 use alloc::format;
+#[cfg(feature = "alloc")]
+use alloc::string::ToString;
 use core::convert::TryInto;
 
 use acid_io::Read;
diff --git a/src/impls/slice.rs b/src/impls/slice.rs
index 4587afc8..c31631c2 100644
--- a/src/impls/slice.rs
+++ b/src/impls/slice.rs
@@ -1,12 +1,12 @@
 //! Implementations of DekuRead and DekuWrite for [T; N] where 0 < N <= 32
 
-use bitvec::prelude::*;
 pub use deku_derive::*;
 
-use crate::{DekuError, DekuRead, DekuWrite};
 
 #[cfg(feature = "const_generics")]
 mod const_generics_impl {
+    use bitvec::prelude::*;
+    use crate::{DekuError, DekuRead, DekuWrite};
     use core::mem::MaybeUninit;
     use std::io::Read;