From e865cbb2e59a95962d7e4d45c31f9ff1e4ba6579 Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Tue, 16 Apr 2019 21:54:19 +0200
Subject: [PATCH] book: resources shared with init must also be `Send`

---
 book/en/src/by-example/types-send-sync.md |  8 +++++
 ci/script.sh                              |  1 +
 examples/shared-with-init.rs              | 38 +++++++++++++++++++++++
 3 files changed, 47 insertions(+)
 create mode 100644 examples/shared-with-init.rs

diff --git a/book/en/src/by-example/types-send-sync.md b/book/en/src/by-example/types-send-sync.md
index 8ec62e6569..632946b9ac 100644
--- a/book/en/src/by-example/types-send-sync.md
+++ b/book/en/src/by-example/types-send-sync.md
@@ -44,6 +44,14 @@ send operation where the initial value is sent from `idle`, which has the lowest
 priority of `0`, to a task with will run with a priority greater than or equal
 to `1`. Thus all late resources need to implement the `Send` trait.
 
+Sharing a resource with `init` can be used to implement late initialization, see
+example below. For that reason, resources shared with `init` must also implement
+the `Send` trait.
+
+``` rust
+{{#include ../../../../examples/shared-with-init.rs}}
+```
+
 ## `Sync`
 
 Similarly, [`Sync`] is a marker trait for "types for which it is safe to share
diff --git a/ci/script.sh b/ci/script.sh
index 7cda1e5e66..0e350d1ffd 100644
--- a/ci/script.sh
+++ b/ci/script.sh
@@ -109,6 +109,7 @@ main() {
                 types
                 not-send
                 not-sync
+                shared-with-init
 
                 generics
                 ramfunc
diff --git a/examples/shared-with-init.rs b/examples/shared-with-init.rs
new file mode 100644
index 0000000000..5ddd2cc3d9
--- /dev/null
+++ b/examples/shared-with-init.rs
@@ -0,0 +1,38 @@
+//! `examples/shared-with-init.rs`
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+extern crate panic_halt;
+
+use cortex_m_semihosting::debug;
+use lm3s6965::Interrupt;
+use rtfm::app;
+
+pub struct MustBeSend;
+
+#[app(device = lm3s6965)]
+const APP: () = {
+    static mut SHARED: Option<MustBeSend> = None;
+
+    #[init(resources = [SHARED])]
+    fn init() {
+        // this `message` will be sent to task `UART0`
+        let message = MustBeSend;
+        *resources.SHARED = Some(message);
+
+        rtfm::pend(Interrupt::UART0);
+    }
+
+    #[interrupt(resources = [SHARED])]
+    fn UART0() {
+        if let Some(message) = resources.SHARED.take() {
+            // `message` has been received
+            drop(message);
+
+            debug::exit(debug::EXIT_SUCCESS);
+        }
+    }
+};