Merge #53

53: Change usage example for statically allocated heap r=adamgreig a=nviennot

The linker needs to know how big the heap is, otherwise, it could place some of the global variables in the heap region.
This commit changes the example code to do that.

Co-authored-by: Nicolas Viennot <nicolas@viennot.biz>

Author: bors[bot]

examples/global_alloc.rs

@@ -16,9 +16,12 @@ static ALLOCATOR: CortexMHeap = CortexMHeap::empty();
 #[entry]
 fn main() -> ! {
     // Initialize the allocator BEFORE you use it
-    let start = cortex_m_rt::heap_start() as usize;
-    let size = 1024; // in bytes
-    unsafe { ALLOCATOR.init(start, size) }
+    {
+        use core::mem::MaybeUninit;
+        const HEAP_SIZE: usize = 1024;
+        static mut HEAP: [MaybeUninit<u8>; HEAP_SIZE] = [MaybeUninit::uninit(); HEAP_SIZE];
+        unsafe { ALLOCATOR.init((&mut HEAP).as_ptr() as usize, HEAP_SIZE) }
+    }
 
     let mut xs = Vec::new();
     xs.push(1);