Fix export level of plugin and procmacro registrars.

src/librustc_metadata/cstore_impl.rs

@@ -256,10 +256,9 @@ provide! { <'tcx> tcx, def_id, other, cdata,
         let cnum = cdata.cnum;
         assert!(cnum != LOCAL_CRATE);
 
-        // If this crate is a plugin and/or a custom derive crate, then
-        // we're not even going to link those in so we skip those crates.
-        if cdata.root.plugin_registrar_fn.is_some() ||
-           cdata.root.macro_derive_registrar.is_some() {
+        // If this crate is a custom derive crate, then we're not even going to
+        // link those in so we skip those crates.
+        if cdata.root.macro_derive_registrar.is_some() {
             return Arc::new(Vec::new())
         }
 

src/librustc_trans/back/symbol_export.rs

@@ -119,7 +119,7 @@ fn exported_symbols_provider_local<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let special_runtime_crate = tcx.is_panic_runtime(LOCAL_CRATE) ||
         tcx.is_compiler_builtins(LOCAL_CRATE);
 
-    let mut reachable_non_generics: DefIdSet = tcx.reachable_set(LOCAL_CRATE).0
+    let reachable_non_generics: DefIdSet = tcx.reachable_set(LOCAL_CRATE).0
         .iter()
         .filter_map(|&node_id| {
             // We want to ignore some FFI functions that are not exposed from
@@ -174,14 +174,6 @@ fn exported_symbols_provider_local<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         })
         .collect();
 
-    if let Some(id) = tcx.sess.derive_registrar_fn.get() {
-        reachable_non_generics.insert(tcx.hir.local_def_id(id));
-    }
-
-    if let Some(id) = tcx.sess.plugin_registrar_fn.get() {
-        reachable_non_generics.insert(tcx.hir.local_def_id(id));
-    }
-
     let mut symbols: Vec<_> = reachable_non_generics
         .iter()
         .map(|&def_id| {
@@ -211,6 +203,16 @@ fn exported_symbols_provider_local<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         })
         .collect();
 
+    if let Some(id) = tcx.sess.derive_registrar_fn.get() {
+        let def_id = tcx.hir.local_def_id(id);
+        symbols.push((ExportedSymbol::NonGeneric(def_id), SymbolExportLevel::C));
+    }
+
+    if let Some(id) = tcx.sess.plugin_registrar_fn.get() {
+        let def_id = tcx.hir.local_def_id(id);
+        symbols.push((ExportedSymbol::NonGeneric(def_id), SymbolExportLevel::C));
+    }
+
     if let Some(_) = *tcx.sess.entry_fn.borrow() {
         let symbol_name = "main".to_string();
         let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(&symbol_name));