extern task

7 files changed, 127 insertions, 33 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec19bd16..22018ebe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   - `#[task_local]`, there must be only one task, similar to a task local
     resource, but (optionally) set-up by init. This is similar to move.
 
+- Improved ergonomics allowing separation of task signatures to actual implementation in extern block `extern "Rust" { #[task(..)] fn t(..); }`.
+
 ### Changed
 
 - [breaking-change] [PR 400] Move dispatchers from extern block to app argument.
diff --git a/book/en/src/migration/migration_v5.md b/book/en/src/migration/migration_v5.md
index 5cf818c5..44af15e2 100644
--- a/book/en/src/migration/migration_v5.md
+++ b/book/en/src/migration/migration_v5.md
@@ -36,7 +36,6 @@ mod app {
 
 This works also for ram functions, see examples/ramfunc.rs
 
-
 ## Module instead of Const
 
 With the support of attributes on modules the `const APP` workaround is not needed.
@@ -125,3 +124,13 @@ struct whateveryouwant {
 ```
 
 would work equally well.
+
+---
+
+## Additions
+
+### Extern tasks
+
+Both software and hardware tasks can now be defined external to the `mod app`. Previously this was possible only by implementing a trampoline calling out the task implementation.  
+
+See examples `examples/extern_binds.rs` and `examples/extern_spawn.rs`.
\ No newline at end of file
diff --git a/examples/extern_binds.rs b/examples/extern_binds.rs
new file mode 100644
index 00000000..632f4ca0
--- /dev/null
+++ b/examples/extern_binds.rs
@@ -0,0 +1,48 @@
+//! examples/extern_binds.rs
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+use cortex_m_semihosting::hprintln;
+use panic_semihosting as _;
+
+// Free function implementing the interrupt bound task `foo`.
+fn foo(_: app::foo::Context) {
+    hprintln!("foo called").ok();
+}
+
+#[rtic::app(device = lm3s6965)]
+mod app {
+    use crate::foo;
+    use cortex_m_semihosting::{debug, hprintln};
+    use lm3s6965::Interrupt;
+
+    #[init]
+    fn init(_: init::Context) -> init::LateResources {
+        rtic::pend(Interrupt::UART0);
+
+        hprintln!("init").unwrap();
+
+        init::LateResources {}
+    }
+
+    #[idle]
+    fn idle(_: idle::Context) -> ! {
+        hprintln!("idle").unwrap();
+
+        rtic::pend(Interrupt::UART0);
+
+        debug::exit(debug::EXIT_SUCCESS);
+
+        loop {
+            cortex_m::asm::nop();
+        }
+    }
+
+    extern "Rust" {
+        #[task(binds = UART0)]
+        fn foo(_: foo::Context);
+    }
+}
diff --git a/examples/extern_spawn.rs b/examples/extern_spawn.rs
new file mode 100644
index 00000000..1be3d512
--- /dev/null
+++ b/examples/extern_spawn.rs
@@ -0,0 +1,35 @@
+//! examples/extern_spawn.rs
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+use cortex_m_semihosting::{debug, hprintln};
+use panic_semihosting as _;
+
+// Free function implementing the spawnable task `foo`.
+fn foo(_c: app::foo::Context, x: i32, y: u32) {
+    hprintln!("foo {}, {}", x, y).unwrap();
+    if x == 2 {
+        debug::exit(debug::EXIT_SUCCESS);
+    }
+    app::foo::spawn(2, 3).unwrap();
+}
+
+#[rtic::app(device = lm3s6965, dispatchers = [SSI0])]
+mod app {
+    use crate::foo;
+
+    #[init]
+    fn init(_c: init::Context) -> init::LateResources {
+        foo::spawn(1, 2).unwrap();
+
+        init::LateResources {}
+    }
+
+    extern "Rust" {
+        #[task()]
+        fn foo(_c: foo::Context, _x: i32, _y: u32);
+    }
+}
diff --git a/macros/src/codegen/hardware_tasks.rs b/macros/src/codegen/hardware_tasks.rs
index e5a8deb9..c9d0297e 100644
--- a/macros/src/codegen/hardware_tasks.rs
+++ b/macros/src/codegen/hardware_tasks.rs
@@ -95,19 +95,21 @@ pub fn codegen(
             locals_pat = Some(pat);
         }
 
-        let attrs = &task.attrs;
-        let context = &task.context;
-        let stmts = &task.stmts;
-        let locals_pat = locals_pat.iter();
-        user_tasks.push(quote!(
-            #(#attrs)*
-            #[allow(non_snake_case)]
-            fn #name(#(#locals_pat,)* #context: #name::Context) {
-                use rtic::Mutex as _;
-
-                #(#stmts)*
-            }
-        ));
+        if !&task.is_extern {
+            let attrs = &task.attrs;
+            let context = &task.context;
+            let stmts = &task.stmts;
+            let locals_pat = locals_pat.iter();
+            user_tasks.push(quote!(
+                #(#attrs)*
+                #[allow(non_snake_case)]
+                fn #name(#(#locals_pat,)* #context: #name::Context) {
+                    use rtic::Mutex as _;
+
+                    #(#stmts)*
+                }
+            ));
+        }
     }
 
     (mod_app, root, user_tasks)
diff --git a/macros/src/codegen/software_tasks.rs b/macros/src/codegen/software_tasks.rs
index dfba193b..833e338d 100644
--- a/macros/src/codegen/software_tasks.rs
+++ b/macros/src/codegen/software_tasks.rs
@@ -99,21 +99,23 @@ pub fn codegen(
             root.push(struct_);
         }
 
-        let context = &task.context;
-        let attrs = &task.attrs;
-        let cfgs = &task.cfgs;
-        let stmts = &task.stmts;
-        let locals_pat = locals_pat.iter();
-        user_tasks.push(quote!(
-            #(#attrs)*
-            #(#cfgs)*
-            #[allow(non_snake_case)]
-            fn #name(#(#locals_pat,)* #context: #name::Context #(,#inputs)*) {
-                use rtic::Mutex as _;
-
-                #(#stmts)*
-            }
-        ));
+        if !&task.is_extern {
+            let context = &task.context;
+            let attrs = &task.attrs;
+            let cfgs = &task.cfgs;
+            let stmts = &task.stmts;
+            let locals_pat = locals_pat.iter();
+            user_tasks.push(quote!(
+                #(#attrs)*
+                #(#cfgs)*
+                #[allow(non_snake_case)]
+                fn #name(#(#locals_pat,)* #context: #name::Context #(,#inputs)*) {
+                    use rtic::Mutex as _;
+
+                    #(#stmts)*
+                }
+            ));
+        }
 
         root.push(module::codegen(
             Context::SoftwareTask(name),
diff --git a/ui/single/extern-interrupt-used.rs b/ui/single/extern-interrupt-used.rs
index 2ba31682..240e7363 100644
--- a/ui/single/extern-interrupt-used.rs
+++ b/ui/single/extern-interrupt-used.rs
@@ -4,8 +4,4 @@
 mod app {
     #[task(binds = UART0)]
     fn a(_: a::Context) {}
-
-    extern "C" {
-        fn UART0();
-    }
 }