Merge #391c-m-rt-v0.7.1

391: Merge cortex-m-rt into this repository r=thejpster a=adamgreig

This PR merges the cortex-m-rt repository (with history) into this repo, inside the `cortex-m-rt` folder which is added to the workspace. The main advantage is easier combined testing of cortex-m with cortex-m-rt (including on-hardware tests e.g. #355), and in the future easier changes across the two projects.

The MSRV of cortex-m-rt is bumped 1.39 -> 1.40 to align it with cortex-m itself.

I've updated the CI to run the same tests and checks as before, and updated references to the old URL.

If/after this is merged, I propose adding a note to the old repo's README and then archiving it.

An alternative to this technique would be adding all the files in one new commit (not preserving history), if anyone thinks that would be neater.

NB: This PR also adds an inline to ITM to fix a clippy hard error.

For future reference, the git work was:

```
cd cortex-m-rt
git filter-repo --to-subdirectory-filter cortex-m-rt
cd ../cortex-m
git remote add rt ../cortex-m-rt
git fetch rt
git merge --allow-unrelated-histories rt/master
```

Co-authored-by: bors[bot] <bors[bot]@users.noreply.github.com>
Co-authored-by: Jonathan 'theJPster' Pallant <github@thejpster.org.uk>
Co-authored-by: Adam Greig <adam@adamgreig.com>
Co-authored-by: Jonas Schievink <jonasschievink@gmail.com>
Co-authored-by: Jorge Aparicio <jorge@japaric.io>
Co-authored-by: Emil Fresk <emil.fresk@gmail.com>
Co-authored-by: Daniel Egger <daniel@eggers-club.de>
Co-authored-by: Niklas Claesson <nicke.claesson@gmail.com>
Co-authored-by: bors[bot] <26634292+bors[bot]@users.noreply.github.com>
Co-authored-by: Vadim Kaushan <admin@disasm.info>

1 files changed, 26 insertions, 0 deletions

diff --git a/cortex-m-rt/tests/compile-fail/entry-soundness.rs b/cortex-m-rt/tests/compile-fail/entry-soundness.rs
new file mode 100644
index 0000000..9fc8ec1
--- /dev/null
+++ b/cortex-m-rt/tests/compile-fail/entry-soundness.rs
@@ -0,0 +1,26 @@
+#![no_main]
+#![no_std]
+
+extern crate cortex_m_rt;
+extern crate panic_halt;
+
+use cortex_m_rt::{entry, exception};
+
+#[entry]
+fn foo() -> ! {
+    static mut COUNT: u64 = 0;
+
+    loop {
+        if *COUNT % 2 == 0 {
+            *COUNT += 1;
+        } else {
+            *COUNT *= 2;
+        }
+    }
+}
+
+#[exception]
+fn SysTick() {
+    // If this was allowed it would lead to a data race as `SysTick` can preempt `foo`
+    foo(); //~ ERROR cannot find function `foo` in this scope
+}