Merge #90

90: turn macros into attributes r=adamgreig a=japaric

This is a PoC implementation of RFC #82. Assuming that we are OK with this implementation we should
add some compile fail tests (e.g. using a function with the wrong signature as the entry point)
before landing this.

Look at the diff of the examples to get an overview of the changes.

cc @rust-embedded/cortex-m

Co-authored-by: Jorge Aparicio <jorge@japaric.io>

1 files changed, 19 insertions, 0 deletions

diff --git a/cortex-m-rt/tests/compile-fail/entry-hidden.rs b/cortex-m-rt/tests/compile-fail/entry-hidden.rs
new file mode 100644
index 0000000..7d74063
--- /dev/null
+++ b/cortex-m-rt/tests/compile-fail/entry-hidden.rs
@@ -0,0 +1,19 @@
+// ignore-test :sadface: it's not possible to prevent this user error at compile time
+// see rust-lang/rust#53975 for details
+
+#![no_main]
+#![no_std]
+
+extern crate cortex_m_rt;
+extern crate panic_semihosting;
+
+mod hidden {
+    use cortex_m_rt::entry;
+
+    // this function needs to be "reachable" (all modules between it and the crate root must be
+    // `pub`) or linking will fail
+    #[entry]
+    fn foo() -> ! { //~ ERROR function is never used
+        loop {}
+    }
+}