also (properly) test nounwind on function definitions

src/test/codegen/nounwind-extern.rs

@@ -1,6 +0,0 @@
-// compile-flags: -O
-
-#![crate_type = "lib"]
-
-// CHECK: Function Attrs: norecurse nounwind
-pub extern fn foo() {}

src/test/codegen/unwind-extern-exports.rs

@@ -0,0 +1,19 @@
+// compile-flags: -C opt-level=0
+
+#![crate_type = "lib"]
+#![feature(unwind_attributes)]
+
+// Make sure these all do *not* get the attribute.
+// We disable optimizations to prevent LLVM from infering the attribute.
+// CHECK-NOT: nounwind
+
+// "C" ABI
+// pub extern fn foo() {} // FIXME right now we don't abort-on-panic but add `nounwind` nevertheless
+#[unwind(allowed)]
+pub extern fn foo_allowed() {}
+
+// "Rust" ABI (`extrn "Rust"` could be removed as all `fn` get it implicitly; we leave it
+// in for clarity.)
+pub extern "Rust" fn bar() {}
+#[unwind(allowed)]
+pub extern "Rust" fn bar_allowed() {}