diff options
Diffstat (limited to 'src/macros.rs')
| -rw-r--r-- | src/macros.rs | 32 |
1 files changed, 22 insertions, 10 deletions
diff --git a/src/macros.rs b/src/macros.rs index 66b75b1..512c932 100644 --- a/src/macros.rs +++ b/src/macros.rs @@ -30,9 +30,12 @@ macro_rules! iprintln { /// `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. /// -/// # Note +/// # 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 @@ -50,15 +53,24 @@ macro_rules! iprintln { /// 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 { - (: $ty:ty = $expr:expr) => { + ($name:ident: $ty:ty = $expr:expr) => { $crate::interrupt::free(|_| { - static mut VAR: Option<$ty> = None; + // 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 { VAR.is_some() }; + let used = unsafe { $name.1 }; if used { None } else { @@ -66,16 +78,16 @@ macro_rules! singleton { #[allow(unsafe_code)] unsafe { - VAR = Some(expr) - } - - #[allow(unsafe_code)] - unsafe { - VAR.as_mut() + $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 |