Merge #120

120: Allow for manual opt-out of CAS features r=japaric a=jamesmunns

I've been working on a bare metal platform lately that does not have CAS (specifically ARMv4 bare metal), and this is not caught by the CPU detection logic in the build.rs. This PR adds a flag that allows for manual specification to avoid CAS features.

Co-authored-by: James Munns <james.munns@ferrous-systems.com>

Cargo.toml

@@ -19,6 +19,12 @@ name = "heapless"
 repository = "https://github.com/japaric/heapless"
 version = "0.5.1"
 
+[features]
+default = ["cas"]
+cas = []
+# only for tests
+__trybuild = []
+
 [target.x86_64-unknown-linux-gnu.dev-dependencies]
 scoped_threadpool = "0.1.8"
 
@@ -31,7 +37,3 @@ hash32 = "0.1.0"
 version = "1"
 optional = true
 default-features = false
-
-[features]
-# only for tests
-__trybuild = []

src/lib.rs

@@ -89,9 +89,9 @@ mod ser;
 
 pub mod binary_heap;
 pub mod i;
-#[cfg(not(armv6m))]
+#[cfg(all(not(armv6m), feature = "cas"))]
 pub mod mpmc;
-#[cfg(not(armv6m))]
+#[cfg(all(not(armv6m), feature = "cas"))]
 pub mod pool;
 pub mod spsc;
 

src/pool/mod.rs

@@ -154,7 +154,6 @@
 //!
 //! [1]: https://static.docs.arm.com/ddi0403/eb/DDI0403E_B_armv7m_arm.pdf
 
-#[cfg(not(armv6m))]
 use core::{any::TypeId, mem, sync::atomic::Ordering};
 use core::{
     cell::UnsafeCell,