From 51500a1d7096395be9162599fae647ec121db91d Mon Sep 17 00:00:00 2001
From: Emil Fresk <emil.fresk@gmail.com>
Date: Thu, 8 Apr 2021 09:12:08 +0200
Subject: [PATCH] Fixed UB in `spawn_at`

---
 examples/type-usage.rs       |  2 +-
 macros/Cargo.toml            |  4 +---
 macros/src/codegen/module.rs | 16 +++++-----------
 src/tq.rs                    |  6 ++++--
 4 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/examples/type-usage.rs b/examples/type-usage.rs
index a7a0d41105..9bb7eb8dd7 100644
--- a/examples/type-usage.rs
+++ b/examples/type-usage.rs
@@ -1,4 +1,4 @@
-//! examples/smallest.rs
+//! examples/type-usage.rs
 
 #![no_main]
 #![no_std]
diff --git a/macros/Cargo.toml b/macros/Cargo.toml
index 8607ce55fd..203a2bb121 100644
--- a/macros/Cargo.toml
+++ b/macros/Cargo.toml
@@ -22,6 +22,4 @@ proc-macro2 = "1"
 proc-macro-error = "1"
 quote = "1"
 syn = "1"
-# rtic-syntax = "0.5.0-alpha.2"
-rtic-syntax = { path = "../../rtic-syntax", version = "0.5.0-alpha.2" }
-
+rtic-syntax = "0.5.0-alpha.2"
diff --git a/macros/src/codegen/module.rs b/macros/src/codegen/module.rs
index ac69a80309..50146c0214 100644
--- a/macros/src/codegen/module.rs
+++ b/macros/src/codegen/module.rs
@@ -414,17 +414,11 @@ pub fn codegen(
 
                                 let tq = unsafe { &mut *#app_path::#tq.as_mut_ptr() };
 
-                                if let Some(mono) = #app_path::#m_ident.as_mut() {
-                                    tq.enqueue_unchecked(
-                                        nr,
-                                        || #enable_interrupt,
-                                        || #pend,
-                                        mono)
-                                } else {
-                                    // We can only use the timer queue if `init` has returned, and it
-                                    // writes the `Some(monotonic)` we are accessing here.
-                                    core::hint::unreachable_unchecked()
-                                }
+                                tq.enqueue_unchecked(
+                                    nr,
+                                    || #enable_interrupt,
+                                    || #pend,
+                                    #app_path::#m_ident.as_mut());
 
                                 Ok(SpawnHandle { marker })
                             })
diff --git a/src/tq.rs b/src/tq.rs
index 3864025924..985e0f8817 100644
--- a/src/tq.rs
+++ b/src/tq.rs
@@ -42,7 +42,7 @@ where
         nr: NotReady<Mono, Task>,
         enable_interrupt: F1,
         pend_handler: F2,
-        mono: &mut Mono,
+        mono: Option<&mut Mono>,
     ) where
         F1: FnOnce(),
         F2: FnOnce(),
@@ -57,7 +57,9 @@ where
 
         if if_heap_max_greater_than_nr {
             if Mono::DISABLE_INTERRUPT_ON_EMPTY_QUEUE && self.0.is_empty() {
-                mono.enable_timer();
+                if let Some(mono) = mono {
+                    mono.enable_timer();
+                }
                 enable_interrupt();
             }