librustc: Make sure to add argument attributes to extern fns from non-local crates.

src/test/run-make/extern-fn-with-union/Makefile

@@ -0,0 +1,8 @@
+-include ../tools.mk
+
+all:
+	$(CC) -std=c99 test.c -c -o $(TMPDIR)/test.o
+	$(AR) rcs $(TMPDIR)/libtest.a $(TMPDIR)/test.o
+	$(RUSTC) testcrate.rs -L $(TMPDIR)
+	$(RUSTC) test.rs -L $(TMPDIR)
+	$(call RUN,test) || exit 1

src/test/run-make/extern-fn-with-union/test.c

@@ -0,0 +1,10 @@
+#include <stdio.h>
+#include <stdint.h>
+
+typedef union TestUnion {
+    uint64_t bits;
+} TestUnion;
+
+uint64_t give_back(TestUnion tu) {
+    return tu.bits;
+}

src/test/run-make/extern-fn-with-union/test.rs

@@ -0,0 +1,34 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+extern crate testcrate;
+
+use std::mem;
+
+#[link(name = "test", kind = "static")]
+extern {
+    fn give_back(tu: testcrate::TestUnion) -> u64;
+}
+
+fn main() {
+    let magic: u64 = 0xDEADBEEF;
+
+    // Let's test calling it cross crate
+    let back = unsafe {
+        testcrate::give_back(mem::transmute(magic))
+    };
+    assert_eq!(magic, back);
+
+    // And just within this crate
+    let back = unsafe {
+        give_back(mem::transmute(magic))
+    };
+    assert_eq!(magic, back);
+}

src/test/run-make/extern-fn-with-union/testcrate.rs

@@ -0,0 +1,20 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![crate_type = "lib"]
+
+pub struct TestUnion {
+    val: u64
+}
+
+#[link(name = "test", kind = "static")]
+extern {
+    pub fn give_back(tu: TestUnion) -> u64;
+}