---

yaml
---
r: 150002
b: refs/heads/try2
c: 17ad504
h: refs/heads/master
v: v3

Author: alexcrichton

[refs]

@@ -5,7 +5,7 @@ refs/heads/snap-stage3: 78a7676898d9f80ab540c6df5d4c9ce35bb50463
 refs/heads/try: 519addf6277dbafccbb4159db4b710c37eaa2ec5
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b
-refs/heads/try2: 0b3df19c6a02a743dae904245c6f98424e75af8c
+refs/heads/try2: 17ad504fef35191fe53874bd2fe77ffd14d8e1b9
 refs/heads/dist-snap: ba4081a5a8573875fed17545846f6f6902c8ba8d
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/try2/src/librustc/metadata/cstore.rs

@@ -143,16 +143,44 @@ impl CStore {
         self.used_link_args.with_mut(|s| s.clear());
     }
 
+    // This method is used when generating the command line to pass through to
+    // system linker. The linker expects undefined symbols on the left of the
+    // command line to be defined in libraries on the right, not the other way
+    // around. For more info, see some comments in the add_used_library function
+    // below.
+    //
+    // In order to get this left-to-right dependency ordering, we perform a
+    // topological sort of all crates putting the leaves at the right-most
+    // positions.
     pub fn get_used_crates(&self, prefer: LinkagePreference)
                            -> Vec<(ast::CrateNum, Option<Path>)> {
+        let mut ordering = Vec::new();
+        fn visit(cstore: &CStore, cnum: ast::CrateNum,
+                 ordering: &mut Vec<ast::CrateNum>) {
+            if ordering.as_slice().contains(&cnum) { return }
+            let meta = cstore.get_crate_data(cnum);
+            for (_, &dep) in meta.cnum_map.borrow().get().iter() {
+                visit(cstore, dep, ordering);
+            }
+            ordering.push(cnum);
+        };
+        for (&num, _) in self.metas.borrow().get().iter() {
+            visit(self, num, &mut ordering);
+        }
+        ordering.as_mut_slice().reverse();
+        let ordering = ordering.as_slice();
         let used_crate_sources = self.used_crate_sources.borrow();
-        used_crate_sources.get()
+        let mut libs = used_crate_sources.get()
             .iter()
             .map(|src| (src.cnum, match prefer {
                 RequireDynamic => src.dylib.clone(),
                 RequireStatic => src.rlib.clone(),
             }))
-            .collect()
+            .collect();
+        libs.sort_by(|&(a, _), &(b, _)| {
+            ordering.position_elem(&a).cmp(&ordering.position_elem(&b))
+        });
+        libs
     }
 
     pub fn add_used_library(&self, lib: ~str, kind: NativeLibaryKind) {