add a test / example about using `static mut` vars in the entry point

1 files changed, 20 insertions, 0 deletions

diff --git a/cortex-m-rt/examples/entry-static.rs b/cortex-m-rt/examples/entry-static.rs
new file mode 100644
index 0000000..1b2e118
--- /dev/null
+++ b/cortex-m-rt/examples/entry-static.rs
@@ -0,0 +1,20 @@
+//! `static mut` variables local to the entry point are safe to use
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+extern crate cortex_m_rt as rt;
+extern crate panic_semihosting;
+
+use rt::entry;
+
+#[entry]
+fn main() -> ! {
+    static mut COUNT: u32 = 0;
+
+    loop {
+        *COUNT += 1;
+    }
+}