--- a/graal/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/processor/LanguageRegistrationTest.java	Thu Jun 04 01:00:44 2015 +0200
+++ b/graal/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/processor/LanguageRegistrationTest.java	Thu Jun 04 08:08:05 2015 +0200
@@ -58,7 +58,7 @@
         }
 
         @Override
-        protected Object findExportedSymbol(String globalName) {
+        protected Object findExportedSymbol(String globalName, boolean onlyExplicit) {
             return null;
         }
 
@@ -86,7 +86,7 @@
         }
 
         @Override
-        protected Object findExportedSymbol(String globalName) {
+        protected Object findExportedSymbol(String globalName, boolean onlyExplicit) {
             return null;
         }
 
@@ -113,7 +113,7 @@
         }
 
         @Override
-        protected Object findExportedSymbol(String globalName) {
+        protected Object findExportedSymbol(String globalName, boolean onlyExplicit) {
             return null;
         }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/vm/ImplicitExplicitExportTest.java	Thu Jun 04 08:08:05 2015 +0200
@@ -0,0 +1,189 @@
+/*
+ * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.truffle.api.test.vm;
+
+import com.oracle.truffle.api.TruffleLanguage;
+import com.oracle.truffle.api.source.Source;
+import com.oracle.truffle.api.vm.TruffleVM;
+import java.io.IOException;
+import java.io.Reader;
+import java.util.Enumeration;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+import static org.junit.Assert.*;
+import org.junit.Before;
+import org.junit.Test;
+
+public class ImplicitExplicitExportTest {
+    private TruffleVM vm;
+
+    @Before
+    public void initializeVM() {
+        vm = TruffleVM.newVM().build();
+        assertTrue("Found " + L1 + " language", vm.getLanguages().containsKey(L1));
+        assertTrue("Found " + L2 + " language", vm.getLanguages().containsKey(L2));
+        assertTrue("Found " + L3 + " language", vm.getLanguages().containsKey(L3));
+    }
+
+    @Test
+    public void explicitExportFound() throws IOException {
+        // @formatter:off
+        vm.eval(L1,
+            "explicit.ahoj=42"
+        );
+        Object ret = vm.eval(L3,
+            "return=ahoj"
+        );
+        // @formatter:on
+        assertEquals("42", ret);
+    }
+
+    @Test
+    public void implicitExportFound() throws IOException {
+        // @formatter:off
+        vm.eval(L1,
+            "implicit.ahoj=42"
+        );
+        Object ret = vm.eval(L3,
+            "return=ahoj"
+        );
+        // @formatter:on
+        assertEquals("42", ret);
+    }
+
+    @Test
+    public void explicitExportPreferred2() throws IOException {
+        // @formatter:off
+        vm.eval(L1,
+            "implicit.ahoj=42"
+        );
+        vm.eval(L2,
+            "explicit.ahoj=43"
+        );
+        Object ret = vm.eval(L3,
+            "return=ahoj"
+        );
+        // @formatter:on
+        assertEquals("Explicit import from L2 is used", "43", ret);
+        assertEquals("Global symbol is also 43", "43", vm.findGlobalSymbol("ahoj").invoke(null));
+    }
+
+    @Test
+    public void explicitExportPreferred1() throws IOException {
+        // @formatter:off
+        vm.eval(L1,
+            "explicit.ahoj=43"
+        );
+        vm.eval(L2,
+            "implicit.ahoj=42"
+        );
+        Object ret = vm.eval(L3,
+            "return=ahoj"
+        );
+        // @formatter:on
+        assertEquals("Explicit import from L2 is used", "43", ret);
+        assertEquals("Global symbol is also 43", "43", vm.findGlobalSymbol("ahoj").invoke(null));
+    }
+
+    private abstract static class AbstractExportImportLanguage extends TruffleLanguage {
+        protected AbstractExportImportLanguage(Env env) {
+            super(env);
+        }
+
+        private final Map<String, String> explicit = new HashMap<>();
+        private final Map<String, String> implicit = new HashMap<>();
+
+        @Override
+        protected Object eval(Source code) throws IOException {
+            Properties p = new Properties();
+            try (Reader r = code.getReader()) {
+                p.load(r);
+            }
+            Enumeration<Object> en = p.keys();
+            while (en.hasMoreElements()) {
+                Object n = en.nextElement();
+                if (n instanceof String) {
+                    String k = (String) n;
+                    if (k.startsWith("explicit.")) {
+                        explicit.put(k.substring(9), p.getProperty(k));
+                    }
+                    if (k.startsWith("implicit.")) {
+                        implicit.put(k.substring(9), p.getProperty(k));
+                    }
+                    if (k.equals("return")) {
+                        return env().importSymbol(p.getProperty(k));
+                    }
+                }
+            }
+            return null;
+        }
+
+        @Override
+        protected Object findExportedSymbol(String globalName, boolean onlyExplicit) {
+            if (explicit.containsKey(globalName)) {
+                return explicit.get(globalName);
+            }
+            if (!onlyExplicit && implicit.containsKey(globalName)) {
+                return implicit.get(globalName);
+            }
+            return null;
+        }
+
+        @Override
+        protected Object getLanguageGlobal() {
+            return null;
+        }
+
+        @Override
+        protected boolean isObjectOfLanguage(Object object) {
+            return false;
+        }
+    }
+
+    private static final String L1 = "application/x-test-import-export-1";
+    private static final String L2 = "application/x-test-import-export-2";
+    private static final String L3 = "application/x-test-import-export-3";
+
+    @TruffleLanguage.Registration(mimeType = L1, name = "ImportExport1")
+    public static final class ExportImportLanguage1 extends AbstractExportImportLanguage {
+        public ExportImportLanguage1(Env env) {
+            super(env);
+        }
+    }
+
+    @TruffleLanguage.Registration(mimeType = L2, name = "ImportExport2")
+    public static final class ExportImportLanguage2 extends AbstractExportImportLanguage {
+        public ExportImportLanguage2(Env env) {
+            super(env);
+        }
+    }
+
+    @TruffleLanguage.Registration(mimeType = L3, name = "ImportExport3")
+    public static final class ExportImportLanguage3 extends AbstractExportImportLanguage {
+        public ExportImportLanguage3(Env env) {
+            super(env);
+        }
+    }
+
+}

--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/TruffleLanguage.java	Thu Jun 04 01:00:44 2015 +0200
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/TruffleLanguage.java	Thu Jun 04 08:08:05 2015 +0200
@@ -96,14 +96,25 @@
      * somebody asks for it (by calling this method).
      * <p>
      * The exported object can either be <code>TruffleObject</code> (e.g. a native object from the
-     * other language) to support interoperability between languages or one of Java primitive
-     * wrappers ( {@link Integer}, {@link Double}, {@link Short}, etc.).
+     * other language) to support inter-operability between languages, {@link String} or one of Java
+     * primitive wrappers ( {@link Integer}, {@link Double}, {@link Short}, {@link Boolean}, etc.).
+     * <p>
+     * The way a symbol becomes <em>exported</em> is language dependant. In general it is preferred
+     * to make the export explicit - e.g. call some function or method to register an object under
+     * specific name. Some languages may however decide to support implicit export of symbols (for
+     * example from global scope, if they have one). However explicit exports should always be
+     * preferred. Implicitly exported object of some name should only be used when there is no
+     * explicit export under such <code>globalName</code>. To ensure so the infrastructure first
+     * asks all known languages for <code>onlyExplicit</code> symbols and only when none is found,
+     * it does one more round with <code>onlyExplicit</code> set to <code>false</code>.
      *
      * @param globalName the name of the global symbol to find
+     * @param onlyExplicit should the language seek for implicitly exported object or only consider
+     *            the explicitly exported ones?
      * @return an exported object or <code>null</code>, if the symbol does not represent anything
      *         meaningful in this language
      */
-    protected abstract Object findExportedSymbol(String globalName);
+    protected abstract Object findExportedSymbol(String globalName, boolean onlyExplicit);
 
     /**
      * Returns global object for the language.
@@ -210,8 +221,8 @@
         }
 
         @Override
-        protected Object findExportedSymbol(TruffleLanguage l, String globalName) {
-            return l.findExportedSymbol(globalName);
+        protected Object findExportedSymbol(TruffleLanguage l, String globalName, boolean onlyExplicit) {
+            return l.findExportedSymbol(globalName, onlyExplicit);
         }
 
         @Override

--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/impl/Accessor.java	Thu Jun 04 01:00:44 2015 +0200
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/impl/Accessor.java	Thu Jun 04 08:08:05 2015 +0200
@@ -46,7 +46,7 @@
             }
 
             @Override
-            protected Object findExportedSymbol(String globalName) {
+            protected Object findExportedSymbol(String globalName, boolean onlyExplicit) {
                 return null;
             }
 
@@ -89,8 +89,8 @@
         return SPI.importSymbol(vm, queryingLang, globalName);
     }
 
-    protected Object findExportedSymbol(TruffleLanguage l, String globalName) {
-        return API.findExportedSymbol(l, globalName);
+    protected Object findExportedSymbol(TruffleLanguage l, String globalName, boolean onlyExplicit) {
+        return API.findExportedSymbol(l, globalName, onlyExplicit);
     }
 
     protected Object languageGlobal(TruffleLanguage l) {

--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/vm/TruffleVM.java	Thu Jun 04 01:00:44 2015 +0200
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/vm/TruffleVM.java	Thu Jun 04 08:08:05 2015 +0200
@@ -104,9 +104,15 @@
                 LOG.log(Level.CONFIG, "Cannot process " + u + " as language definition", ex);
                 continue;
             }
-            Language l = new Language(p);
-            for (String mimeType : l.getMimeTypes()) {
-                langs.put(mimeType, l);
+            for (int cnt = 1;; cnt++) {
+                String prefix = "language" + cnt + ".";
+                if (p.getProperty(prefix + "name") == null) {
+                    break;
+                }
+                Language l = new Language(prefix, p);
+                for (String mimeType : l.getMimeTypes()) {
+                    langs.put(mimeType, l);
+                }
             }
         }
     }
@@ -327,12 +333,22 @@
         Object global = null;
         for (Language dl : langs.values()) {
             TruffleLanguage l = dl.getImpl();
-            obj = SPI.findExportedSymbol(l, globalName);
+            obj = SPI.findExportedSymbol(l, globalName, true);
             if (obj != null) {
                 global = SPI.languageGlobal(l);
                 break;
             }
         }
+        if (obj == null) {
+            for (Language dl : langs.values()) {
+                TruffleLanguage l = dl.getImpl();
+                obj = SPI.findExportedSymbol(l, globalName, false);
+                if (obj != null) {
+                    global = SPI.languageGlobal(l);
+                    break;
+                }
+            }
+        }
         return obj == null ? null : new Symbol(obj, global);
     }
 
@@ -399,8 +415,10 @@
     public final class Language {
         private final Properties props;
         private TruffleLanguage impl;
+        private final String prefix;
 
-        Language(Properties props) {
+        Language(String prefix, Properties props) {
+            this.prefix = prefix;
             this.props = props;
         }
 
@@ -412,7 +430,7 @@
         public Set<String> getMimeTypes() {
             TreeSet<String> ts = new TreeSet<>();
             for (int i = 0;; i++) {
-                String mt = props.getProperty("mimeType." + i);
+                String mt = props.getProperty(prefix + "mimeType." + i);
                 if (mt == null) {
                     break;
                 }
@@ -427,12 +445,12 @@
          * @return string giving the language a name
          */
         public String getName() {
-            return props.getProperty("name");
+            return props.getProperty(prefix + "name");
         }
 
         TruffleLanguage getImpl() {
             if (impl == null) {
-                String n = props.getProperty("className");
+                String n = props.getProperty(prefix + "className");
                 try {
                     Class<?> langClazz = Class.forName(n, true, loader());
                     Constructor<?> constructor = langClazz.getConstructor(Env.class);
@@ -459,7 +477,17 @@
                 if (l == ownLang) {
                     continue;
                 }
-                Object obj = SPI.findExportedSymbol(l, globalName);
+                Object obj = SPI.findExportedSymbol(l, globalName, true);
+                if (obj != null) {
+                    return obj;
+                }
+            }
+            for (Language dl : uniqueLang) {
+                TruffleLanguage l = dl.getImpl();
+                if (l == ownLang) {
+                    continue;
+                }
+                Object obj = SPI.findExportedSymbol(l, globalName, false);
                 if (obj != null) {
                     return obj;
                 }
@@ -478,8 +506,8 @@
         }
 
         @Override
-        public Object findExportedSymbol(TruffleLanguage l, String globalName) {
-            return super.findExportedSymbol(l, globalName);
+        public Object findExportedSymbol(TruffleLanguage l, String globalName, boolean onlyExplicit) {
+            return super.findExportedSymbol(l, globalName, onlyExplicit);
         }
 
         @Override

--- a/graal/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/LanguageRegistrationProcessor.java	Thu Jun 04 01:00:44 2015 +0200
+++ b/graal/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/LanguageRegistrationProcessor.java	Thu Jun 04 08:08:05 2015 +0200
@@ -37,33 +37,50 @@
 
 @SupportedAnnotationTypes("com.oracle.truffle.api.*")
 public final class LanguageRegistrationProcessor extends AbstractProcessor {
+    private final List<TypeElement> registrations = new ArrayList<>();
+
     @Override
     public SourceVersion getSupportedSourceVersion() {
         return SourceVersion.latest();
     }
 
-    private void createProviderFile(TypeElement language, Registration annotation) {
+    private void generateFile(List<TypeElement> languages) {
         String filename = "META-INF/truffle/language";
-        try {
-            FileObject file = processingEnv.getFiler().createResource(StandardLocation.CLASS_OUTPUT, "", filename, language);
-            Properties p = new Properties();
-            String className = processingEnv.getElementUtils().getBinaryName(language).toString();
-            p.setProperty("name", annotation.name());
-            p.setProperty("className", className);
+        Properties p = new Properties();
+        int cnt = 0;
+        for (TypeElement l : languages) {
+            Registration annotation = l.getAnnotation(Registration.class);
+            if (annotation == null) {
+                continue;
+            }
+            String prefix = "language" + ++cnt + ".";
+            String className = processingEnv.getElementUtils().getBinaryName(l).toString();
+            p.setProperty(prefix + "name", annotation.name());
+            p.setProperty(prefix + "className", className);
             String[] mimes = annotation.mimeType();
             for (int i = 0; i < mimes.length; i++) {
-                p.setProperty("mimeType." + i, mimes[i]);
+                p.setProperty(prefix + "mimeType." + i, mimes[i]);
             }
-            try (OutputStream os = file.openOutputStream()) {
-                p.store(os, "Generated by " + LanguageRegistrationProcessor.class.getName());
+        }
+        if (cnt > 0) {
+            try {
+                FileObject file = processingEnv.getFiler().createResource(StandardLocation.CLASS_OUTPUT, "", filename, languages.toArray(new Element[0]));
+                try (OutputStream os = file.openOutputStream()) {
+                    p.store(os, "Generated by " + LanguageRegistrationProcessor.class.getName());
+                }
+            } catch (IOException e) {
+                processingEnv.getMessager().printMessage(Kind.ERROR, e.getMessage(), languages.get(0));
             }
-        } catch (IOException e) {
-            processingEnv.getMessager().printMessage(Kind.ERROR, e.getMessage(), language);
         }
     }
 
     @Override
     public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
+        if (roundEnv.processingOver()) {
+            generateFile(registrations);
+            registrations.clear();
+            return true;
+        }
         for (Element e : roundEnv.getElementsAnnotatedWith(Registration.class)) {
             Registration annotation = e.getAnnotation(Registration.class);
             if (annotation != null && e.getKind() == ElementKind.CLASS) {
@@ -103,7 +120,7 @@
                     continue;
                 }
                 assertNoErrorExpected(e);
-                createProviderFile((TypeElement) e, annotation);
+                registrations.add((TypeElement) e);
             }
         }
 

--- a/graal/com.oracle.truffle.interop/src/com/oracle/truffle/interop/SymbolInvokerImpl.java	Thu Jun 04 01:00:44 2015 +0200
+++ b/graal/com.oracle.truffle.interop/src/com/oracle/truffle/interop/SymbolInvokerImpl.java	Thu Jun 04 08:08:05 2015 +0200
@@ -40,6 +40,15 @@
 
     @Override
     protected Object invoke(Object symbol, Object... arr) throws IOException {
+        if (symbol instanceof String) {
+            return symbol;
+        }
+        if (symbol instanceof Number) {
+            return symbol;
+        }
+        if (symbol instanceof Boolean) {
+            return symbol;
+        }
         ForeignObjectAccessNode callMain = ForeignObjectAccessNode.getAccess(Execute.create(Receiver.create(), arr.length));
         CallTarget callMainTarget = Truffle.getRuntime().createCallTarget(new TemporaryRoot(callMain, (TruffleObject) symbol, arr));
         VirtualFrame frame = Truffle.getRuntime().createVirtualFrame(arr, UNUSED_FRAMEDESCRIPTOR);

--- a/graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/SLMain.java	Thu Jun 04 01:00:44 2015 +0200
+++ b/graal/com.oracle.truffle.sl/src/com/oracle/truffle/sl/SLMain.java	Thu Jun 04 08:08:05 2015 +0200
@@ -368,7 +368,7 @@
     }
 
     @Override
-    protected Object findExportedSymbol(String globalName) {
+    protected Object findExportedSymbol(String globalName, boolean onlyExplicit) {
         for (SLFunction f : context.getFunctionRegistry().getFunctions()) {
             if (globalName.equals(f.getName())) {
                 return f;

--- a/mx/suite.py	Thu Jun 04 01:00:44 2015 +0200
+++ b/mx/suite.py	Thu Jun 04 08:08:05 2015 +0200
@@ -1085,6 +1085,7 @@
       ],
       "checkstyle" : "com.oracle.graal.graph",
       "javaCompliance" : "1.7",
+      "annotationProcessors" : ["com.oracle.truffle.dsl.processor"],
       "workingSets" : "API,Truffle,Test",
       "jacoco" : "exclude",
     },