bare0_6

examples/bare0.rs

@@ -18,45 +18,43 @@ extern crate panic_halt;
 // Minimal runtime / startup for Cortex-M microcontrollers
 use cortex_m_rt::entry;
 
+use core::cell::UnsafeCell;
+struct U32 {
+    data: UnsafeCell<u32>,
+}
+
 // a constant (cannot be changed at run-time)
 const X_INIT: u32 = 0xffffffff;
 
 // global mutabale variables (changed using unsafe code)
-static mut X: u32 = X_INIT;
-static mut Y: u32 = 0;
+static X: U32 = U32 {
+    data: UnsafeCell::new(X_INIT),
+};
+static Y: U32 = U32 {
+    data: UnsafeCell::new(0),
+};
+
+unsafe impl Sync for U32 {}
 
 #[entry]
 fn main() -> ! {
     // local mutabale variable (changed in safe code)
-    let mut x = read_x();
+    let mut x = read_u32(&X);
     
     loop {
         x = x.wrapping_add(1); // <- place breakpoint here (3)
-        write_x(read_x().wrapping_add(1));
-        write_y(read_x());
-        assert!(x == read_x() && read_x() == read_y() );
-    }
-}
-
-fn read_x() -> u32 {
-    return unsafe { X };
-}
-
-fn read_y() -> u32 {
-    return unsafe { Y };
-}
-
-fn write_x(x: u32) {
-    unsafe {
-        X = x;
+            write_u32(&X, read_u32(&X).wrapping_add(1) );
+            write_u32(&Y, read_u32(&X));
+            assert!(x == read_u32(&X) && read_u32(&X) == read_u32(&Y) );
     }
 }
 
-fn write_y(y: u32) {
-    unsafe {
-        Y = y
+fn read_u32(uint: &U32) -> u32 {
+    return unsafe{ *uint.data.get()};
 }
 
+fn write_u32(write_to: &U32, value: u32) {
+    unsafe{ *write_to.data.get() = value };
 }
 
 // 0. Compile/build the example in debug (dev) mode.