document how to use the heap and a dynamic allocator

CHANGELOG.md

@@ -5,6 +5,15 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- Documentation and an example about how to use the heap and a dynamic memory
+  allocator.
+
+### Changed
+
+- Bumped the `cortex-m-rt` dependency to v0.2.2
+
 ## [v0.1.6] - 2017-05-26
 
 ### Added

Cargo.toml

@@ -10,7 +10,7 @@ version = "0.1.6"
 
 [dependencies]
 cortex-m = "0.2.6"
-cortex-m-rt = "0.2.0"
+cortex-m-rt = "0.2.2"
 
 [profile.release]
 lto = true

examples/allocator.rs

@@ -0,0 +1,71 @@
+//! How to use the heap and a dynamic memory allocator
+//!
+//! To compile this example you'll need to build the collections crate as part
+//! of the Xargo sysroot. To do that change the Xargo.toml file to look like
+//! this:
+//!
+//! ``` text
+//! [dependencies.core]
+//! [dependencies.collections] # new
+//!
+//! [dependencies.compiler_builtins]
+//! features = ["mem"]
+//! git = "https://github.com/rust-lang-nursery/compiler-builtins"
+//! stage = 1
+//! ```
+//!
+//! 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(collections)]
+#![feature(used)]
+#![no_std]
+
+// This is the allocator crate; you can use a different one
+extern crate alloc_cortex_m;
+#[macro_use]
+extern crate collections;
+#[macro_use]
+extern crate cortex_m;
+extern crate cortex_m_rt;
+
+use cortex_m::asm;
+
+fn main() {
+    // Initialize the allocator
+    unsafe {
+        extern "C" {
+            // Start of the heap
+            static mut _sheap: usize;
+        }
+
+        // Size of the heap in words (1 word = 4 bytes)
+        // WARNING: The bigger the heap the greater the chance to run into a
+        // stack overflow (collision between the stack and the heap)
+        const SIZE: isize = 256;
+
+        // End of the heap
+        let _eheap = (&mut _sheap as *mut _).offset(SIZE);
+
+        alloc_cortex_m::init(&mut _sheap as *mut _, _eheap);
+    }
+
+    // Growable array allocated on the heap
+    let xs = vec![0, 1, 2];
+    hprintln!("{:?}", xs);
+}
+
+// As we are not using interrupts, we just register a dummy catch all handler
+#[allow(dead_code)]
+#[used]
+#[link_section = ".rodata.interrupts"]
+static INTERRUPTS: [extern "C" fn(); 240] = [default_handler; 240];
+
+extern "C" fn default_handler() {
+    asm::bkpt();
+}

gen-examples.sh

@@ -11,6 +11,7 @@ main() {
         crash
         register-interrupt-handler
         override-exception-handler
+        allocator
     )
 
     rm -rf src/examples

src/examples/_3_crash.rs

@@ -27,7 +27,7 @@
 //! $2 = cortex_m::exception::Exception::HardFault
 //!
 //! (gdb) # Where did we come from?
-//! (gdb) print _e
+//! (gdb) backtrace
 //! ```
 //!
 //! ```

src/examples/_6_allocator.rs

@@ -0,0 +1,75 @@
+//! How to use the heap and a dynamic memory allocator
+//!
+//! To compile this example you'll need to build the collections crate as part
+//! of the Xargo sysroot. To do that change the Xargo.toml file to look like
+//! this:
+//!
+//! ``` text
+//! [dependencies.core]
+//! [dependencies.collections] # new
+//!
+//! [dependencies.compiler_builtins]
+//! features = ["mem"]
+//! git = "https://github.com/rust-lang-nursery/compiler-builtins"
+//! stage = 1
+//! ```
+//!
+//! 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(collections)]
+//! #![feature(used)]
+//! #![no_std]
+//! 
+//! // This is the allocator crate; you can use a different one
+//! extern crate alloc_cortex_m;
+//! #[macro_use]
+//! extern crate collections;
+//! #[macro_use]
+//! extern crate cortex_m;
+//! extern crate cortex_m_rt;
+//! 
+//! use cortex_m::asm;
+//! 
+//! fn main() {
+//!     // Initialize the allocator
+//!     unsafe {
+//!         extern "C" {
+//!             // Start of the heap
+//!             static mut _sheap: usize;
+//!         }
+//! 
+//!         // Size of the heap in words (1 word = 4 bytes)
+//!         // WARNING: The bigger the heap the greater the chance to run into a
+//!         // stack overflow (collision between the stack and the heap)
+//!         const SIZE: isize = 256;
+//! 
+//!         // End of the heap
+//!         let _eheap = (&mut _sheap as *mut _).offset(SIZE);
+//! 
+//!         alloc_cortex_m::init(&mut _sheap as *mut _, _eheap);
+//!     }
+//! 
+//!     // Growable array allocated on the heap
+//!     let xs = vec![0, 1, 2];
+//!     hprintln!("{:?}", xs);
+//! }
+//! 
+//! // As we are not using interrupts, we just register a dummy catch all handler
+//! #[allow(dead_code)]
+//! #[used]
+//! #[link_section = ".rodata.interrupts"]
+//! static INTERRUPTS: [extern "C" fn(); 240] = [default_handler; 240];
+//! 
+//! extern "C" fn default_handler() {
+//!     asm::bkpt();
+//! }
+//! ```
+// Auto-generated. Do not modify.

src/examples/mod.rs

@@ -6,3 +6,4 @@ pub mod _2_panic;
 pub mod _3_crash;
 pub mod _4_register_interrupt_handler;
 pub mod _5_override_exception_handler;
+pub mod _6_allocator;

src/lib.rs

@@ -111,24 +111,24 @@
 //!
 //! - Flash the program
 //!
-//! ```
+//! ``` text
 //! # Launch OpenOCD on a terminal
 //! $ openocd -f (..)
 //! ```
 //!
-//! ```
+//! ``` text
 //! # Start debug session
 //! $ arm-none-eabi-gdb target/..
 //! ```
 //!
 //! **NOTE** As of nightly-2017-05-14 or so and cortex-m-quickstart v0.1.6 you
-//! can simply run `cargo run` or `cargo run --example $ex` to build and flash
+//! can simply run `cargo run` or `cargo run --example $example` to build the
-//! the program, and immediately start a debug session. IOW, it lets you omit
+//! program, and immediately start a debug session. IOW, it lets you omit the
 //! `arm-none-eabi-gdb` command.
 //!
-//! ```
+//! ``` text
 //! $ cargo run --example hello
-//! > # drop you into GDB session
+//! > # drops you into a GDB session
 //! ```
 //!
 //! # Examples
@@ -242,7 +242,7 @@
 //!
 //! Error message:
 //!
-//! ```
+//! ``` text
 //! $ xargo build
 //! error: linking with `arm-none-eabi-ld` failed: exit code: 1
 //!     |