diff --git a/src/hal/cortex_common/irq.rs b/src/hal/cortex_common/irq.rs
index ac9083c9..5a4e5560 100644
--- a/src/hal/cortex_common/irq.rs
+++ b/src/hal/cortex_common/irq.rs
@@ -16,7 +16,7 @@
 //! Disabling and enabling interrupts
 
 use core::ops::Drop;
-#[cfg(not(test))]
+#[cfg(target_os = "none")]
 use core::intrinsics::abort;
 
 /// Phantom type to indicate that interrupts are disabled.
@@ -43,25 +43,25 @@ impl Drop for NoInterrupts {
   }
 }
 
-#[cfg(not(test))]
+#[cfg(target_os = "none")]
 static mut irq_level : usize = 0;
 
 /// Disables all interrupts except Reset, HardFault, and NMI.
 /// Note that this is reference counted: if `disable_irqs` is called
 /// twice then interrupts will only be re-enabled upon the second call
 /// to `enable_irqs`.
-#[cfg(not(test))]
+#[cfg(target_os = "none")]
 #[inline(always)]
 unsafe fn disable_irqs() {
   asm!("cpsid i" :::: "volatile");
   irq_level += 1;
 }
 
-#[cfg(test)]
+#[cfg(not(target_os = "none"))]
 unsafe fn disable_irqs() { unimplemented!() }
 
 /// Enables all interrupts except Reset, HardFault, and NMI.
-#[cfg(not(test))]
+#[cfg(target_os = "none")]
 #[inline(always)]
 unsafe fn enable_irqs() {
   if irq_level == 0 {
@@ -75,5 +75,5 @@ unsafe fn enable_irqs() {
   }
 }
 
-#[cfg(test)]
+#[cfg(not(target_os = "none"))]
 unsafe fn enable_irqs() { unimplemented!() }
diff --git a/src/hal/cortex_m3/isr.rs b/src/hal/cortex_m3/isr.rs
index c653b733..a7cac1a5 100644
--- a/src/hal/cortex_m3/isr.rs
+++ b/src/hal/cortex_m3/isr.rs
@@ -34,7 +34,6 @@ extern {
   fn isr_reserved_1();
 }
 
-#[cfg(not(test))]
 #[no_mangle]
 pub unsafe extern fn isr_handler_wrapper() {
   asm!(".weak isr_nmi, isr_hardfault, isr_mmfault, isr_busfault
diff --git a/src/hal/cortex_m3/lock.rs b/src/hal/cortex_m3/lock.rs
index 84a4cafc..e7fd6e62 100644
--- a/src/hal/cortex_m3/lock.rs
+++ b/src/hal/cortex_m3/lock.rs
@@ -29,7 +29,7 @@ pub struct Guard<'a>(&'a Lock);
 
 pub static STATIC_LOCK: Lock = Lock { locked: Unsafe { value: 0, marker1: InvariantType } };
 
-#[cfg(not(test))]
+#[cfg(target_arch = "arm")]
 #[inline(always)]
 unsafe fn exclusive_load(addr: *const u32) -> u32 {
   let mut value: u32;
@@ -42,10 +42,10 @@ unsafe fn exclusive_load(addr: *const u32) -> u32 {
   value
 }
 
-#[cfg(test)]
+#[cfg(not(target_arch = "arm"))]
 unsafe fn exclusive_load(addr: *const u32) -> u32 { unimplemented!() }
 
-#[cfg(not(test))]
+#[cfg(target_arch = "arm")]
 #[inline(always)]
 unsafe fn exclusive_store(addr: *mut u32, value: u32) -> bool {
   let mut success: u32;
@@ -58,7 +58,7 @@ unsafe fn exclusive_store(addr: *mut u32, value: u32) -> bool {
   success == 0
 }
 
-#[cfg(test)]
+#[cfg(not(target_arch = "arm"))]
 unsafe fn exclusive_store(addr: *mut u32, value: u32) -> bool {
   unimplemented!()
 }
diff --git a/src/hal/cortex_m3/sched.rs b/src/hal/cortex_m3/sched.rs
index 531be10c..de62b4a8 100644
--- a/src/hal/cortex_m3/sched.rs
+++ b/src/hal/cortex_m3/sched.rs
@@ -28,17 +28,17 @@ pub fn switch_context() {
 }
 
 /// Sets task stack pointer (PSP).
-#[cfg(not(test))]
+#[cfg(target_arch = "arm")]
 #[inline(always)]
 pub fn set_task_stack_pointer(val: u32) {
   unsafe { asm!("msr psp, $0" :: "r"(val) :: "volatile") };
 }
 
-#[cfg(test)]
+#[cfg(not(target_arch = "arm"))]
 pub fn set_task_stack_pointer(val: u32) { unimplemented!() }
 
 /// Returns task stack pointer (PSP).
-#[cfg(not(test))]
+#[cfg(target_arch = "arm")]
 #[inline(always)]
 pub fn get_task_stack_pointer() -> u32 {
   let mut val: u32;
@@ -46,11 +46,11 @@ pub fn get_task_stack_pointer() -> u32 {
   val
 }
 
-#[cfg(test)]
+#[cfg(not(target_arch = "arm"))]
 pub fn get_task_stack_pointer() -> u32 { unimplemented!() }
 
 /// Returns current stack pointer (SP, which may be PSP or MSP).
-#[cfg(not(test))]
+#[cfg(target_arch = "arm")]
 #[inline(always)]
 pub fn get_current_stack_pointer() -> u32 {
   let mut val: u32;
@@ -58,7 +58,7 @@ pub fn get_current_stack_pointer() -> u32 {
   val
 }
 
-#[cfg(test)]
+#[cfg(not(target_arch = "arm"))]
 pub fn get_current_stack_pointer() -> u32 { unimplemented!() }
 
 /// State, that's saved by hardware upon entering an ISR.
@@ -92,11 +92,11 @@ impl SavedState {
 // TODO(farcaller): this should actually kill the task.
 // TODO(bgamari): It should also unlock anything the task holds
 /// Default handler for task that tries to return.
-#[cfg(not(test))]
+#[cfg(target_os = "none")]
 unsafe fn task_finished() {
-  asm!("bkpt" :::: "volatile");
+  core::intrinsics::breakpoint();
 }
 
-#[cfg(test)]
+#[cfg(not(target_os = "none"))]
 unsafe fn task_finished() { unimplemented!() }
 
diff --git a/src/hal/isr.rs b/src/hal/isr.rs
index 21ab6abb..722439fd 100644
--- a/src/hal/isr.rs
+++ b/src/hal/isr.rs
@@ -21,7 +21,6 @@
 #[cfg(feature = "cpu_cortex-m3")]
 #[path="cortex_m3/isr.rs"] pub mod isr_cortex_m3;
 
-// TODO(mcoffin): create cortex-m4 isr module
 #[cfg(feature = "cpu_cortex-m4")]
 #[path="cortex_m3/isr.rs"] pub mod isr_cortex_m4;
 
diff --git a/src/hal/mod.rs b/src/hal/mod.rs
index af07aa04..49d7917c 100644
--- a/src/hal/mod.rs
+++ b/src/hal/mod.rs
@@ -48,5 +48,5 @@ pub mod stack;
 pub mod timer;
 pub mod uart;
 
-#[cfg(not(test))]
+#[cfg(target_os = "none")]
 pub mod isr;
diff --git a/src/lib.rs b/src/lib.rs
index f1bf914d..896462b2 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -48,7 +48,8 @@ STM32F403/407).
 #![feature(no_std)]
 
 #[macro_use] extern crate core;
-#[cfg(not(test))] extern crate rlibc;
+#[cfg(target_os = "none")]
+extern crate rlibc;
 
 #[macro_use] #[no_link] extern crate ioreg;
 extern crate volatile_cell;
@@ -66,7 +67,7 @@ pub mod os;
 /// for some items in the `std` namespace.
 ///
 /// TODO(farcaller): clean up when fixed.
-#[cfg(not(test))]
+#[cfg(target_os = "none")]
 pub mod std {
   pub use core::cmp;  // used for #[derive(Eq)] until fixed in rust.
   pub use core::option;
diff --git a/src/util/shared.rs b/src/util/shared.rs
index ccc60d28..7e47bbd1 100644
--- a/src/util/shared.rs
+++ b/src/util/shared.rs
@@ -34,7 +34,7 @@ mod dummy_irq {
 
   impl NoInterrupts {
     pub fn new() -> NoInterrupts {
-      NoInterrupts;
+      NoInterrupts
     }
   }
 }
diff --git a/src/util/support.rs b/src/util/support.rs
index 25814664..327f4451 100644
--- a/src/util/support.rs
+++ b/src/util/support.rs
@@ -15,25 +15,15 @@
 
 //! Support functions currently required by the linker for bare-metal targets.
 
-#[doc(hidden)]
-#[cfg(test)]
-#[no_stack_check]
-#[no_mangle]
-pub extern fn breakpoint() { unimplemented!() }
-
-/// Call the debugger.
-#[cfg(all(not(test), target_arch = "arm"))]
-#[no_stack_check]
-#[no_mangle]
-pub extern fn breakpoint() {
-  unsafe { asm!("bkpt") }
-}
+pub use core::intrinsics::breakpoint;
 
 /// Call the debugger and halts execution.
 #[no_stack_check]
 #[no_mangle]
 pub extern fn abort() -> ! {
-  breakpoint();
+  unsafe {
+    breakpoint();
+  }
   loop {}
 }
 
@@ -49,26 +39,26 @@ pub extern fn __aeabi_memset(dest: *mut u8, size: usize, value: u32) {
   }
 }
 
-#[cfg(all(not(test), target_arch = "arm"))]
+#[cfg(target_arch = "arm")]
 #[inline(always)]
 /// NOP instruction
 pub fn nop() {
   unsafe { asm!("nop" :::: "volatile"); }
 }
 
-#[cfg(test)]
+#[cfg(not(target_arch = "arm"))]
 /// NOP instruction (mock)
 pub fn nop() {
 }
 
-#[cfg(all(not(test), target_arch = "arm"))]
+#[cfg(target_arch = "arm")]
 #[inline(always)]
 /// WFI instruction
 pub fn wfi() {
     unsafe { asm!("wfi" :::: "volatile"); }
 }
 
-#[cfg(test)]
+#[cfg(not(target_arch = "arm"))]
 /// WFI instruction (mock)
 pub fn wfi() {
 }