initialize singletons at runtime

Author: japaric

Cargo.toml

@@ -13,6 +13,7 @@ version = "0.4.2"
 aligned = "0.1.1"
 bare-metal = "0.1.0"
 volatile-register = "0.2.0"
+untagged-option = "0.1.1"
 
 [features]
-cm7-r0p1 = []
+cm7-r0p1 = []

src/lib.rs

@@ -15,6 +15,7 @@
 
 extern crate aligned;
 extern crate bare_metal;
+extern crate untagged_option;
 extern crate volatile_register;
 
 #[macro_use]
@@ -31,3 +32,4 @@ pub mod peripheral;
 pub mod register;
 
 pub use peripheral::Peripherals;
+pub use untagged_option::UntaggedOption;

src/macros.rs

@@ -54,13 +54,14 @@ macro_rules! singleton {
     (: $ty:ty = $expr:expr) => {
         $crate::interrupt::free(|_| unsafe {
             static mut USED: bool = false;
-            static mut VAR: $ty = $expr;
+            static mut VAR: $crate::UntaggedOption<$ty> = $crate::UntaggedOption { none: () };
 
             if USED {
                 None
             } else {
                 USED = true;
-                let var: &'static mut _ = &mut VAR;
+                VAR.some = $expr;
+                let var: &'static mut _ = &mut VAR.some;
                 Some(var)
             }
         })