move out most of text

see https://github.com/rust-embedded/book/pull/20

examples/allocator.rs

@@ -11,27 +11,19 @@
 
 #![feature(alloc)]
 #![feature(alloc_error_handler)]
-#![feature(lang_items)]
 #![no_main]
 #![no_std]
 
-// This is the allocator crate; you can use a different one
-extern crate alloc_cortex_m;
-#[macro_use]
-extern crate alloc;
-extern crate cortex_m;
-#[macro_use]
-extern crate cortex_m_rt as rt;
-extern crate cortex_m_semihosting as sh;
-extern crate panic_semihosting;
+extern crate panic_halt;
 
 use core::alloc::Layout;
 use core::fmt::Write;
 
+use alloc::vec;
 use alloc_cortex_m::CortexMHeap;
 use cortex_m::asm;
-use rt::ExceptionFrame;
-use sh::hio;
+use cortex_m_rt::entry;
+use cortex_m_semihosting::hio;
 
 // this is the allocator the application will use
 #[global_allocator]
@@ -39,11 +31,10 @@ static ALLOCATOR: CortexMHeap = CortexMHeap::empty();
 
 const HEAP_SIZE: usize = 1024; // in bytes
 
-entry!(main);
-
+#[entry]
 fn main() -> ! {
     // Initialize the allocator BEFORE you use it
-    unsafe { ALLOCATOR.init(rt::heap_start() as usize, HEAP_SIZE) }
+    unsafe { ALLOCATOR.init(cortex_m_rt::heap_start() as usize, HEAP_SIZE) }
 
     // Growable array allocated on the heap
     let xs = vec![0, 1, 2];
@@ -56,21 +47,8 @@ fn main() -> ! {
 
 // define what happens in an Out Of Memory (OOM) condition
 #[alloc_error_handler]
-#[no_mangle]
-pub fn alloc_error(_layout: Layout) -> ! {
+fn alloc_error(_layout: Layout) -> ! {
     asm::bkpt();
 
     loop {}
 }
-
-exception!(HardFault, hard_fault);
-
-fn hard_fault(ef: &ExceptionFrame) -> ! {
-    panic!("HardFault at {:#?}", ef);
-}
-
-exception!(*, default_handler);
-
-fn default_handler(irqn: i16) {
-    panic!("Unhandled exception (IRQn = {})", irqn);
-}