1 files changed, 114 insertions, 0 deletions
diff --git a/src/macros.rs b/src/macros.rs
new file mode 100644
index 0000000..512c932
--- /dev/null
+++ b/src/macros.rs
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+/// Macro for sending a formatted string through an ITM channel
+#[macro_export]
+macro_rules! iprint {
+    ($channel:expr, $s:expr) => {
+        $crate::itm::write_str($channel, $s);
+    };
+    ($channel:expr, $($arg:tt)*) => {
+        $crate::itm::write_fmt($channel, format_args!($($arg)*));
+    };
+}
+
+/// Macro for sending a formatted string through an ITM channel, with a newline.
+#[macro_export]
+macro_rules! iprintln {
+    ($channel:expr) => {
+        $crate::itm::write_str($channel, "\n");
+    };
+    ($channel:expr, $fmt:expr) => {
+        $crate::itm::write_str($channel, concat!($fmt, "\n"));
+    };
+    ($channel:expr, $fmt:expr, $($arg:tt)*) => {
+        $crate::itm::write_fmt($channel, format_args!(concat!($fmt, "\n"), $($arg)*));
+    };
+}
+
+/// Macro to create a mutable reference to a statically allocated value
+///
+/// This macro returns a value with type `Option<&'static mut $ty>`. `Some($expr)` will be returned
+/// the first time the macro is executed; further calls will return `None`. To avoid `unwrap`ping a
+/// `None` variant the caller must ensure that the macro is called from a function that's executed
+/// at most once in the whole lifetime of the program.
+///
+/// # Notes
+/// This macro is unsound on multi core systems.
+///
+/// For debuggability, you can set an explicit name for a singleton.  This name only shows up the
+/// the debugger and is not referencable from other code.  See example below.
+///
+/// # Example
+///
+/// ``` no_run
+/// use cortex_m::singleton;
+///
+/// fn main() {
+///     // OK if `main` is executed only once
+///     let x: &'static mut bool = singleton!(: bool = false).unwrap();
+///
+///     let y = alias();
+///     // BAD this second call to `alias` will definitively `panic!`
+///     let y_alias = alias();
+/// }
+///
+/// fn alias() -> &'static mut bool {
+///     singleton!(: bool = false).unwrap()
+/// }
+///
+/// fn singleton_with_name() {
+///     // A name only for debugging purposes
+///     singleton!(FOO_BUFFER: [u8; 1024] = [0u8; 1024]);
+/// }
+/// ```
+#[macro_export]
+macro_rules! singleton {
+    ($name:ident: $ty:ty = $expr:expr) => {
+        $crate::interrupt::free(|_| {
+            // this is a tuple of a MaybeUninit and a bool because using an Option here is
+            // problematic:  Due to niche-optimization, an Option could end up producing a non-zero
+            // initializer value which would move the entire static from `.bss` into `.data`...
+            static mut $name: (::core::mem::MaybeUninit<$ty>, bool) =
+                (::core::mem::MaybeUninit::uninit(), false);
+
+            #[allow(unsafe_code)]
+            let used = unsafe { $name.1 };
+            if used {
+                None
+            } else {
+                let expr = $expr;
+
+                #[allow(unsafe_code)]
+                unsafe {
+                    $name.1 = true;
+                    $name.0 = ::core::mem::MaybeUninit::new(expr);
+                    Some(&mut *$name.0.as_mut_ptr())
+                }
+            }
+        })
+    };
+    (: $ty:ty = $expr:expr) => {
+        $crate::singleton!(VAR: $ty = $expr)
+    };
+}
+
+/// ``` compile_fail
+/// use cortex_m::singleton;
+///
+/// fn foo() {
+///     // check that the call to `uninitialized` requires unsafe
+///     singleton!(: u8 = std::mem::uninitialized());
+/// }
+/// ```
+#[allow(dead_code)]
+const CFAIL: () = ();
+
+/// ```
+/// #![deny(unsafe_code)]
+/// use cortex_m::singleton;
+///
+/// fn foo() {
+///     // check that calls to `singleton!` don't trip the `unsafe_code` lint
+///     singleton!(: u8 = 0);
+/// }
+/// ```
+#[allow(dead_code)]
+const CPASS: () = ();