diff --git a/rt/emul/mini/src/main/java/java/lang/reflect/AnnotatedElement.java b/rt/emul/mini/src/main/java/java/lang/reflect/AnnotatedElement.java
diff --git a/rt/vm/pom.xml b/rt/vm/pom.xml
@@ -67,7 +67,7 @@
                   </archive>
               </configuration>
           </plugin>
-         <plugin>
+          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-javadoc-plugin</artifactId>
              <configuration>
@@ -119,4 +119,26 @@
       <scope>test</scope>
     </dependency>
   </dependencies>
+  <profiles>
+      <profile>
+          <id>target15</id>
+          <build>
+              <plugins>
+                  <plugin>
+                      <groupId>org.apache.maven.plugins</groupId>
+                      <artifactId>maven-compiler-plugin</artifactId>
+                      <configuration>
+                          <compilerId>javac</compilerId>
+                          <source>8</source>
+                          <testSource>1.5</testSource>
+                          <testTarget>1.5</testTarget>
+                          <compilerArgs>
+                              <arg>-Xlint:deprecation</arg>
+                          </compilerArgs>
+                      </configuration>
+                  </plugin>
+              </plugins>
+          </build>
+      </profile>
+  </profiles>
 </project>
diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/AbstractStackMapper.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/AbstractStackMapper.java
@@ -0,0 +1,128 @@
+/**
+ * Back 2 Browser Bytecode Translator
+ * Copyright (C) 2012-2018 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * This program 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 for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. Look for COPYING file in the top folder.
+ * If not, see http://opensource.org/licenses/GPL-2.0.
+ */
+package org.apidesign.vm4brwsr;
+
+import java.io.IOException;
+import org.apidesign.vm4brwsr.ByteCodeParser.TypeArray;
+
+abstract class AbstractStackMapper {
+    public abstract void clear();
+
+    public abstract void syncWithFrameStack(final TypeArray frameStack);
+
+    public final CharSequence pushI() {
+        return pushT(VarType.INTEGER);
+    }
+
+    public final CharSequence pushL() {
+        return pushT(VarType.LONG);
+    }
+
+    public final CharSequence pushF() {
+        return pushT(VarType.FLOAT);
+    }
+
+    public final CharSequence pushD() {
+        return pushT(VarType.DOUBLE);
+    }
+
+    public final CharSequence pushA() {
+        return pushT(VarType.REFERENCE);
+    }
+
+    public abstract CharSequence pushT(final int type);
+
+    abstract void assign(Appendable out, int varType, CharSequence s) throws IOException;
+
+    abstract void replace(Appendable out, int varType, String format, CharSequence... arr)
+    throws IOException;
+
+    abstract void flush(Appendable out) throws IOException;
+
+    public abstract boolean isDirty();
+
+    public final CharSequence popI(Appendable out) throws IOException {
+        return popT(out, VarType.INTEGER);
+    }
+
+    public final CharSequence popL(Appendable out) throws IOException {
+        return popT(out, VarType.LONG);
+    }
+
+    public final CharSequence popF(Appendable out) throws IOException {
+        return popT(out, VarType.FLOAT);
+    }
+
+    public final CharSequence popD(Appendable out) throws IOException {
+        return popT(out, VarType.DOUBLE);
+    }
+
+    public final CharSequence popA(Appendable out) throws IOException {
+        return popT(out, VarType.REFERENCE);
+    }
+
+    public abstract CharSequence popT(Appendable out, final int type) throws IOException;
+
+    public abstract CharSequence popValue(Appendable out) throws IOException;
+
+    public abstract Variable pop(Appendable out) throws IOException;
+
+    public abstract void pop(Appendable out, final int count) throws IOException;
+
+    public final CharSequence getI(Appendable out, final int indexFromTop) throws IOException {
+        return getT(out, indexFromTop, VarType.INTEGER);
+    }
+
+    public final CharSequence getL(Appendable out, final int indexFromTop) throws IOException {
+        return getT(out, indexFromTop, VarType.LONG);
+    }
+
+    public final CharSequence getF(Appendable out, final int indexFromTop) throws IOException {
+        return getT(out, indexFromTop, VarType.FLOAT);
+    }
+
+    public final CharSequence getD(Appendable out, final int indexFromTop) throws IOException {
+        return getT(out, indexFromTop, VarType.DOUBLE);
+    }
+
+    public final CharSequence getA(Appendable out, final int indexFromTop) throws IOException {
+        return getT(out, indexFromTop, VarType.REFERENCE);
+    }
+
+    public final CharSequence getT(Appendable out, final int indexFromTop, final int type) throws IOException {
+        return getT(out, indexFromTop, type, true);
+    }
+    public abstract CharSequence getT(Appendable out, final int indexFromTop, final int type, boolean clear) throws IOException;
+
+    public abstract Variable get(Appendable out, final int indexFromTop) throws IOException;
+
+    public static Variable getVariable(final int typeAndIndex) {
+        final int type = typeAndIndex & 0xff;
+        final int index = typeAndIndex >> 8;
+
+        return Variable.getStackVariable(type, index);
+    }
+
+    abstract boolean alwaysUseGt();
+
+    abstract int initCode(Appendable out) throws IOException;
+
+    abstract void finishStatement(Appendable out) throws IOException;
+
+    abstract void caughtException(Appendable out, String e) throws IOException;
+}
diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/ByteCodeToJavaScript.java
@@ -406,6 +406,13 @@ private String compileImpl(Appendable out, final String cn) throws IOException {
         return "";
     }
 
+    private boolean versionCheck() throws IOException {
+        if (jc.getMajor_version() < 50) {
+            return false;
+        }
+        return true;
+    }
+
     private StringArray findJavaScriptResources(byte[] arr, final String cn) throws IOException {
         if (arr == null) {
             return null;
@@ -498,25 +505,18 @@ private boolean generateMethod(Appendable out, String destObject, String name, M
         out.append(") {").append("\n");
 
         final byte[] byteCodes = m.getCode();
-        if (byteCodes == null || jc.getMajor_version() < 50) {
-            if (byteCodes == null) {
-                byte[] defaultAttr = m.getDefaultAttribute();
-                if (defaultAttr != null) {
-                    out.append("  return ");
-                    AnnotationParser ap = new GenerateAnno(out, true, false);
-                    ap.parseDefault(defaultAttr, jc);
-                    out.append(";\n");
-                } else {
-                    if (debug(out, "  throw 'no code found for ")) {
-                       out.append(jc.getClassName()).append('.')
-                       .append(m.getName()).append("';\n");
-                    }
-                }
+        if (byteCodes == null) {
+            byte[] defaultAttr = m.getDefaultAttribute();
+            if (defaultAttr != null) {
+                out.append("  return ");
+                AnnotationParser ap = new GenerateAnno(out, true, false);
+                ap.parseDefault(defaultAttr, jc);
+                out.append(";\n");
             } else {
-                out.append("  throw 'Class file version for " + jc.getClassName() + " is " + jc.getMajor_version() + "."
-                    + jc.getMinor_version() + " - recompile with -target 1.6 (at least)';\n"
-            );
-
+                if (debug(out, "  throw 'no code found for ")) {
+                   out.append(jc.getClassName()).append('.')
+                   .append(m.getName()).append("';\n");
+                }
             }
             if (defineProp) {
                 out.append("}});");
@@ -526,7 +526,12 @@ private boolean generateMethod(Appendable out, String destObject, String name, M
             return defineProp;
         }
 
-        final StackMapper smapper = new StackMapper();
+        final AbstractStackMapper smapper;
+        if (versionCheck()) {
+            smapper = new StackMapper();
+        } else {
+            smapper = new OldStackMapper();
+        }
 
         if (!m.isStatic()) {
             out.append("  var ").append(" lcA0 = this;\n");
@@ -550,7 +555,7 @@ private boolean generateMethod(Appendable out, String destObject, String name, M
         return defineProp;
     }
 
-    static int generateIf(Appendable out, StackMapper mapper, byte[] byteCodes,
+    static int generateIf(Appendable out, AbstractStackMapper mapper, byte[] byteCodes,
         int i, final CharSequence v2, final CharSequence v1,
         final String test, int topMostLabel
     ) throws IOException {
@@ -559,7 +564,7 @@ static int generateIf(Appendable out, StackMapper mapper, byte[] byteCodes,
         out.append("if ((").append(v1)
            .append(") ").append(test).append(" (")
            .append(v2).append(")) ");
-        goTo(out, i, indx, topMostLabel);
+        goTo(out, i, indx, topMostLabel, mapper.alwaysUseGt());
         return i + 2;
     }
 
@@ -1108,13 +1113,13 @@ private static String outputArg(Appendable out, String[] args, int indx) throws
     }
 
     final void emitNoFlush(
-        Appendable out, StackMapper sm,
+        Appendable out, AbstractStackMapper sm,
         final String format, final CharSequence... params
     ) throws IOException {
         emitImpl(out, format, params);
     }
     static final void emit(
-        final Appendable out, StackMapper sm, final String format, final CharSequence... params
+        final Appendable out, AbstractStackMapper sm, final String format, final CharSequence... params
     ) throws IOException {
         sm.flush(out);
         emitImpl(out, format, params);
@@ -1144,8 +1149,9 @@ static void emitImpl(final Appendable out,
         out.append(format, processed, length);
     }
 
-    void generateCatch(Appendable out, TrapData[] traps, int current, int topMostLabel) throws IOException {
+    void generateCatch(Appendable out, AbstractStackMapper mapper, TrapData[] traps, int current, int topMostLabel, boolean useGt) throws IOException {
         out.append("} catch (e) {\n");
+        out.append("    e = vm.java_lang_Class(false).bck2BrwsrThrwrbl(e);\n");
         int finallyPC = -1;
         for (TrapData e : traps) {
             if (e == null) {
@@ -1154,25 +1160,29 @@ void generateCatch(Appendable out, TrapData[] traps, int current, int topMostLab
             if (e.catch_cpx != 0) { //not finally
                 final String classInternalName = jc.getClassName(e.catch_cpx);
                 addReference(out, classInternalName);
-                out.append("e = vm.java_lang_Class(false).bck2BrwsrThrwrbl(e);");
-                out.append("if (e['$instOf_" + mangleClassName(classInternalName) + "']) {");
-                out.append("var stA0 = e;");
-                goTo(out, current, e.handler_pc, topMostLabel);
-                out.append("}\n");
+                out.append("    if (e['$instOf_" + mangleClassName(classInternalName) + "']) {\n");
+                mapper.caughtException(out, "e");
+                goTo(out, current, e.handler_pc, topMostLabel, useGt);
+                out.append("    }\n");
             } else {
                 finallyPC = e.handler_pc;
             }
         }
         if (finallyPC == -1) {
             out.append("throw e;");
         } else {
-            out.append("var stA0 = e;");
-            goTo(out, current, finallyPC, topMostLabel);
+            mapper.caughtException(out, "e");
+            goTo(out, current, finallyPC, topMostLabel, useGt);
         }
         out.append("\n}");
     }
 
-    static void goTo(Appendable out, int current, int to, int canBack) throws IOException {
+    static void goTo(Appendable out, int current, int to, int canBack, boolean useGt) throws IOException {
+        if (useGt) {
+            out.append("{ gt = " + to + "; continue X_0; }");
+            return;
+        }
+
         if (to < current) {
             if (canBack < to) {
                 out.append("{ gt = 0; continue X_" + to + "; }");
@@ -1185,14 +1195,14 @@ static void goTo(Appendable out, int current, int to, int canBack) throws IOExce
     }
 
     static void emitIf(
-        Appendable out, StackMapper sm, String pattern, CharSequence param, int current, int to, int canBack
+        Appendable out, AbstractStackMapper sm, String pattern, CharSequence param, int current, int to, int canBack
     ) throws IOException {
         sm.flush(out);
         emitImpl(out, pattern, param);
-        goTo(out, current, to, canBack);
+        goTo(out, current, to, canBack, sm.alwaysUseGt());
     }
 
-    void generateNewArray(Appendable out, int atype, final StackMapper smapper) throws IOException, IllegalStateException {
+    void generateNewArray(Appendable out, int atype, final AbstractStackMapper smapper) throws IOException, IllegalStateException {
         String jvmType;
         switch (atype) {
             case 4: jvmType = "[Z"; break;
@@ -1207,10 +1217,10 @@ void generateNewArray(Appendable out, int atype, final StackMapper smapper) thro
         }
         emit(out, smapper,
             "var @2 = Array.prototype['newArray__Ljava_lang_Object_2ZLjava_lang_String_2Ljava_lang_Object_2I'](true, '@3', null, @1);",
-             smapper.popI(), smapper.pushA(), jvmType);
+             smapper.popI(out), smapper.pushA(), jvmType);
     }
 
-    void generateANewArray(Appendable out, int type, final StackMapper smapper) throws IOException {
+    void generateANewArray(Appendable out, int type, final AbstractStackMapper smapper) throws IOException {
         String typeName = jc.getClassName(type);
         String ref = "null";
         if (typeName.startsWith("[")) {
@@ -1221,10 +1231,10 @@ void generateANewArray(Appendable out, int type, final StackMapper smapper) thro
         }
         emit(out, smapper,
             "var @2 = Array.prototype['newArray__Ljava_lang_Object_2ZLjava_lang_String_2Ljava_lang_Object_2I'](false, @3, @4, @1);",
-             smapper.popI(), smapper.pushA(), typeName, ref);
+             smapper.popI(out), smapper.pushA(), typeName, ref);
     }
 
-    int generateMultiANewArray(Appendable out, int type, final byte[] byteCodes, int i, final StackMapper smapper) throws IOException {
+    int generateMultiANewArray(Appendable out, int type, final byte[] byteCodes, int i, final AbstractStackMapper smapper) throws IOException {
         String typeName = jc.getClassName(type);
         int dim = readUByte(byteCodes, ++i);
         StringBuilder dims = new StringBuilder();
@@ -1233,7 +1243,7 @@ int generateMultiANewArray(Appendable out, int type, final byte[] byteCodes, int
             if (d != 0) {
                 dims.insert(1, ",");
             }
-            dims.insert(1, smapper.popI());
+            dims.insert(1, smapper.popI(out));
         }
         dims.append(']');
         String fn = "null";
@@ -1247,59 +1257,59 @@ int generateMultiANewArray(Appendable out, int type, final byte[] byteCodes, int
         return i;
     }
 
-    int generateTableSwitch(Appendable out, int i, final byte[] byteCodes, final StackMapper smapper, int topMostLabel) throws IOException {
+    int generateTableSwitch(Appendable out, int i, final byte[] byteCodes, final AbstractStackMapper smapper, int topMostLabel) throws IOException {
         int table = i / 4 * 4 + 4;
         int dflt = i + readInt4(byteCodes, table);
         table += 4;
         int low = readInt4(byteCodes, table);
         table += 4;
         int high = readInt4(byteCodes, table);
         table += 4;
-        final CharSequence swVar = smapper.popValue();
+        final CharSequence swVar = smapper.popValue(out);
         smapper.flush(out);
         out.append("switch (").append(swVar).append(") {\n");
         while (low <= high) {
             int offset = i + readInt4(byteCodes, table);
             table += 4;
-            out.append("  case " + low).append(":"); goTo(out, i, offset, topMostLabel); out.append('\n');
+            out.append("  case " + low).append(":"); goTo(out, i, offset, topMostLabel, smapper.alwaysUseGt()); out.append('\n');
             low++;
         }
         out.append("  default: ");
-        goTo(out, i, dflt, topMostLabel);
+        goTo(out, i, dflt, topMostLabel, smapper.alwaysUseGt());
         out.append("\n}");
         i = table - 1;
         return i;
     }
 
-    int generateLookupSwitch(Appendable out, int i, final byte[] byteCodes, final StackMapper smapper, int topMostLabel) throws IOException {
+    int generateLookupSwitch(Appendable out, int i, final byte[] byteCodes, final AbstractStackMapper smapper, int topMostLabel) throws IOException {
         int table = i / 4 * 4 + 4;
         int dflt = i + readInt4(byteCodes, table);
         table += 4;
         int n = readInt4(byteCodes, table);
         table += 4;
-        final CharSequence swVar = smapper.popValue();
+        final CharSequence swVar = smapper.popValue(out);
         smapper.flush(out);
         out.append("switch (").append(swVar).append(") {\n");
         while (n-- > 0) {
             int cnstnt = readInt4(byteCodes, table);
             table += 4;
             int offset = i + readInt4(byteCodes, table);
             table += 4;
-            out.append("  case " + cnstnt).append(": "); goTo(out, i, offset, topMostLabel); out.append('\n');
+            out.append("  case " + cnstnt).append(": "); goTo(out, i, offset, topMostLabel, smapper.alwaysUseGt()); out.append('\n');
         }
         out.append("  default: ");
-        goTo(out, i, dflt, topMostLabel);
+        goTo(out, i, dflt, topMostLabel, smapper.alwaysUseGt());
         out.append("\n}");
         i = table - 1;
         return i;
     }
 
-    void generateInstanceOf(Appendable out, int indx, final StackMapper smapper) throws IOException {
+    void generateInstanceOf(Appendable out, int indx, final AbstractStackMapper smapper) throws IOException {
         String type = jc.getClassName(indx);
         if (!type.startsWith("[")) {
             emit(out, smapper,
                     "var @2 = @1 != null && @1['$instOf_@3'] ? 1 : 0;",
-                 smapper.popA(), smapper.pushI(),
+                 smapper.popA(out), smapper.pushI(),
                  mangleClassName(type));
         } else {
             int cnt = 0;
@@ -1312,24 +1322,24 @@ void generateInstanceOf(Appendable out, int indx, final StackMapper smapper) thr
                 type = "vm." + mangleClassName(component);
                 emit(out, smapper,
                     "var @2 = Array.prototype['isInstance__ZLjava_lang_Object_2ILjava_lang_Object_2'](@1, @4, @3);",
-                    smapper.popA(), smapper.pushI(),
+                    smapper.popA(out), smapper.pushI(),
                     type, "" + cnt
                 );
             } else {
                 emit(out, smapper,
                     "var @2 = Array.prototype['isInstance__ZLjava_lang_Object_2Ljava_lang_String_2'](@1, '@3');",
-                    smapper.popA(), smapper.pushI(), type
+                    smapper.popA(out), smapper.pushI(), type
                 );
             }
         }
     }
 
-    void generateCheckcast(Appendable out, int indx, final StackMapper smapper) throws IOException {
+    void generateCheckcast(Appendable out, int indx, final AbstractStackMapper smapper) throws IOException {
         String type = jc.getClassName(indx);
         if (!type.startsWith("[")) {
             emitNoFlush(out, smapper,
                  "if (@1 !== null && !@1['$instOf_@2']) vm.java_lang_Class(false).castEx(@1, '@3');",
-                 smapper.getT(0, VarType.REFERENCE, false), mangleClassName(type), type.replace('/', '.'));
+                 smapper.getT(out, 0, VarType.REFERENCE, false), mangleClassName(type), type.replace('/', '.'));
         } else {
             int cnt = 0;
             while (type.charAt(cnt) == '[') {
@@ -1341,12 +1351,12 @@ void generateCheckcast(Appendable out, int indx, final StackMapper smapper) thro
                 type = "vm." + mangleClassName(component);
                 emitNoFlush(out, smapper,
                     "if (@1 !== null && !Array.prototype['isInstance__ZLjava_lang_Object_2ILjava_lang_Object_2'](@1, @3, @2)) vm.java_lang_Class(false).castEx(@1, '');",
-                     smapper.getT(0, VarType.REFERENCE, false), type, "" + cnt
+                     smapper.getT(out, 0, VarType.REFERENCE, false), type, "" + cnt
                 );
             } else {
                 emitNoFlush(out, smapper,
                     "if (@1 !== null && !Array.prototype['isInstance__ZLjava_lang_Object_2Ljava_lang_String_2'](@1, '@2')) vm.java_lang_Class(false).castEx(@1, '');",
-                     smapper.getT(0, VarType.REFERENCE, false), type
+                     smapper.getT(out, 0, VarType.REFERENCE, false), type
                 );
             }
         }

diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/ClassDataCache.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/ClassDataCache.java
diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/IndyHandler.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/IndyHandler.java
@@ -32,12 +32,12 @@ abstract class IndyHandler {
 
     static class Ctx {
         final Appendable out;
-        final StackMapper stackMapper;
+        final AbstractStackMapper stackMapper;
         final ByteCodeToJavaScript byteCodeToJavaScript;
         final ByteCodeParser.BootMethodData bm;
         final String[] mt;
 
-        Ctx(Appendable out, StackMapper m, ByteCodeToJavaScript bc, String[] methodAndType, ByteCodeParser.BootMethodData bm) {
+        Ctx(Appendable out, AbstractStackMapper m, ByteCodeToJavaScript bc, String[] methodAndType, ByteCodeParser.BootMethodData bm) {
             this.out = out;
             this.stackMapper = m;
             this.byteCodeToJavaScript = bc;

diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/LoopCode.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/LoopCode.java
diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/MetafactoryHandler.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/MetafactoryHandler.java
@@ -78,14 +78,14 @@ protected boolean handle(Ctx ctx) throws IOException {
             fixedArgsCount = cnt.length();
             final CharSequence[] vars = new CharSequence[fixedArgsCount];
             for (int j = fixedArgsCount - 1; j >= 0; --j) {
-                vars[j] = ctx.stackMapper.popValue();
+                vars[j] = ctx.stackMapper.popValue(ctx.out);
             }
 
             assert returnType[0] == 'L';
 
             ctx.stackMapper.flush(ctx.out);
 
-            final Variable samVar = ctx.stackMapper.pushA();
+            final CharSequence samVar = ctx.stackMapper.pushA();
             ctx.out.append("var ").append(samVar).append(" = ").append(interfaceToCreate).append(".constructor.$class.$lambda([");
 
             String sep = "";

diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/OldStackMapper.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/OldStackMapper.java
@@ -0,0 +1,132 @@
+/**
+ * Back 2 Browser Bytecode Translator
+ * Copyright (C) 2012-2018 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * This program 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 for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. Look for COPYING file in the top folder.
+ * If not, see http://opensource.org/licenses/GPL-2.0.
+ */
+package org.apidesign.vm4brwsr;
+
+import java.io.IOException;
+
+final class OldStackMapper extends AbstractStackMapper {
+    int counter;
+    int flushed;
+
+    OldStackMapper() {
+    }
+
+    @Override
+    public void clear() {
+    }
+
+    @Override
+    public void syncWithFrameStack(ByteCodeParser.TypeArray frameStack) {
+    }
+
+    @Override
+    int initCode(Appendable out) throws IOException {
+        out.append("    var gt = 0;\n");
+        out.append("    var stack = [];\n");
+        out.append("    X_0: for (;;) {\n");
+        return 1;
+    }
+
+    @Override
+    public CharSequence pushT(int type) {
+        return Variable.getStackVariable(VarType.REFERENCE, ++counter);
+    }
+
+    @Override
+    void assign(Appendable out, int varType, CharSequence s) throws IOException {
+        out.append("stack.push(").append(s).append(");");
+    }
+
+    @Override
+    void replace(Appendable out, int varType, String format, CharSequence... arr) throws IOException {
+        out.append("stack[stack.length - 1] = ");
+        ByteCodeToJavaScript.emitImpl(out, format, arr);
+        out.append(";\n");
+    }
+
+    @Override
+    void flush(Appendable out) throws IOException {
+    }
+
+    @Override
+    void finishStatement(Appendable out) throws IOException {
+        while (flushed < counter) {
+            out.append("stack.push(").append(Variable.getStackVariable(VarType.REFERENCE, ++flushed)).append(");\n");
+        }
+        out.append("}\n");
+    }
+
+    @Override
+    public boolean isDirty() {
+        return false;
+    }
+
+    @Override
+    public CharSequence popT(Appendable out, int type) throws IOException {
+        Variable v = Variable.getStackVariable(VarType.REFERENCE, ++counter);
+        out.append("var ").append(v).append(" = stack.pop();\n");
+        flushed = counter;
+        return v;
+    }
+
+    @Override
+    public CharSequence popValue(Appendable out) throws IOException {
+        return pop(out);
+    }
+
+    @Override
+    public Variable pop(Appendable out) throws IOException {
+        Variable v = Variable.getStackVariable(VarType.REFERENCE, ++counter);
+        out.append("var ").append(v).append(" = stack.pop();\n");
+        flushed = counter;
+        return v;
+    }
+
+    @Override
+    public void pop(Appendable out, int count) throws IOException {
+        while (count-- > 0) {
+            out.append("stack.pop();");
+        }
+    }
+
+    @Override
+    public CharSequence getT(Appendable out, int indexFromTop, int type, boolean clear) throws IOException {
+        Variable v = Variable.getStackVariable(VarType.REFERENCE, ++counter);
+        out.append("var ").append(v).append(" = stack[stack.length - " + (indexFromTop + 1) + "];\n");
+        flushed = counter;
+        return v;
+    }
+
+    @Override
+    public Variable get(Appendable out, int indexFromTop) throws IOException {
+        Variable v = Variable.getStackVariable(VarType.REFERENCE, ++counter);
+        out.append("var ").append(v).append(" = stack[stack.length - " + (indexFromTop + 1) + "];\n");
+        flushed = counter;
+        return v;
+    }
+
+    @Override
+    boolean alwaysUseGt() {
+        return true;
+    }
+
+    @Override
+    void caughtException(Appendable out, String e) throws IOException {
+        out.append("stack = [").append(e).append("];");
+    }
+}
diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/StackMapper.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/StackMapper.java
@@ -20,7 +20,7 @@
 import java.io.IOException;
 import org.apidesign.vm4brwsr.ByteCodeParser.TypeArray;
 
-final class StackMapper {
+final class StackMapper extends AbstractStackMapper {
     private final TypeArray stackTypeIndexPairs;
     private final StringArray stackValues;
     private boolean dirty;
@@ -45,34 +45,17 @@ public void syncWithFrameStack(final TypeArray frameStack) {
         }
     }
 
-    public Variable pushI() {
-        return pushT(VarType.INTEGER);
-    }
-
-    public Variable pushL() {
-        return pushT(VarType.LONG);
-    }
-
-    public Variable pushF() {
-        return pushT(VarType.FLOAT);
-    }
-
-    public Variable pushD() {
-        return pushT(VarType.DOUBLE);
-    }
-
-    public Variable pushA() {
-        return pushT(VarType.REFERENCE);
-    }
-
+    @Override
     public Variable pushT(final int type) {
         return getVariable(pushTypeImpl(type));
     }
 
+    @Override
     void assign(Appendable out, int varType, CharSequence s) throws IOException {
         pushTypeAndValue(varType, s);
     }
 
+    @Override
     void replace(Appendable out, int varType, String format, CharSequence... arr) 
     throws IOException {
         StringBuilder sb = new StringBuilder();
@@ -84,7 +67,12 @@ void replace(Appendable out, int varType, String format, CharSequence... arr)
         final int value = (last << 8) | (varType & 0xff);
         stackTypeIndexPairs.set(last, value);
     }
+
+    @Override
+    void finishStatement(Appendable out) throws IOException {
+    }
 
+    @Override
     void flush(Appendable out) throws IOException {
         int count = stackTypeIndexPairs.getSize();
         for (int i = 0; i < count; i++) {
@@ -98,80 +86,43 @@ void flush(Appendable out) throws IOException {
         dirty = false;
     }
 
+    @Override
     public boolean isDirty() {
         return dirty;
     }
 
-    public CharSequence popI() {
-        return popT(VarType.INTEGER);
-    }
-
-    public CharSequence popL() {
-        return popT(VarType.LONG);
-    }
-
-    public CharSequence popF() {
-        return popT(VarType.FLOAT);
-    }
-
-    public CharSequence popD() {
-        return popT(VarType.DOUBLE);
-    }
-
-    public CharSequence popA() {
-        return popT(VarType.REFERENCE);
-    }
-
-    public CharSequence popT(final int type) {
-        final CharSequence variable = getT(0, type);
+    @Override
+    public CharSequence popT(Appendable out, final int type) throws IOException {
+        final CharSequence variable = getT(out, 0, type);
         popImpl(1);
         return variable;
     }
 
-    public CharSequence popValue() {
-        final CharSequence variable = getT(0, -1);
+    @Override
+    public CharSequence popValue(Appendable out) throws IOException {
+        final CharSequence variable = getT(out, 0, -1);
         popImpl(1);
         return variable;
     }
+    @Override
     public Variable pop(Appendable out) throws IOException {
         flush(out);
-        final Variable variable = get(0);
+        final Variable variable = get(out, 0);
         popImpl(1);
         return variable;
     }
 
-    public void pop(final int count) {
+    @Override
+    public void pop(Appendable out, final int count) {
         final int stackSize = stackTypeIndexPairs.getSize();
         if (count > stackSize) {
             throw new IllegalStateException("Stack underflow");
         }
         popImpl(count);
     }
 
-    public CharSequence getI(final int indexFromTop) {
-        return getT(indexFromTop, VarType.INTEGER);
-    }
-
-    public CharSequence getL(final int indexFromTop) {
-        return getT(indexFromTop, VarType.LONG);
-    }
-
-    public CharSequence getF(final int indexFromTop) {
-        return getT(indexFromTop, VarType.FLOAT);
-    }
-
-    public CharSequence getD(final int indexFromTop) {
-        return getT(indexFromTop, VarType.DOUBLE);
-    }
-
-    public CharSequence getA(final int indexFromTop) {
-        return getT(indexFromTop, VarType.REFERENCE);
-    }
-
-    public CharSequence getT(final int indexFromTop, final int type) {
-        return getT(indexFromTop, type, true);
-    }
-    public CharSequence getT(final int indexFromTop, final int type, boolean clear) {
+    @Override
+    public CharSequence getT(Appendable out, final int indexFromTop, final int type, boolean clear) {
         final int stackSize = stackTypeIndexPairs.getSize();
         if (indexFromTop >= stackSize) {
             throw new IllegalStateException("Stack underflow");
@@ -189,7 +140,8 @@ public CharSequence getT(final int indexFromTop, final int type, boolean clear)
         return getVariable(stackValue);
     }
 
-    public Variable get(final int indexFromTop) {
+    @Override
+    public Variable get(Appendable out, final int indexFromTop) {
         final int stackSize = stackTypeIndexPairs.getSize();
         if (indexFromTop >= stackSize) {
             throw new IllegalStateException("Stack underflow");
@@ -232,10 +184,18 @@ private void popImpl(final int count) {
         stackTypeIndexPairs.setSize(stackSize - count);
     }
 
-    public Variable getVariable(final int typeAndIndex) {
-        final int type = typeAndIndex & 0xff;
-        final int index = typeAndIndex >> 8;
+    @Override
+    boolean alwaysUseGt() {
+        return false;
+    }
+
+    @Override
+    int initCode(Appendable out) throws IOException {
+        return 0;
+    }
 
-        return Variable.getStackVariable(type, index);
+    @Override
+    void caughtException(Appendable out, String e) throws IOException {
+        out.append("var stA0 = ").append(e).append(";");
     }
 }
diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/StringConcatHandler.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/StringConcatHandler.java
@@ -38,13 +38,13 @@ protected boolean handle(Ctx ctx) throws IOException {
         fixedArgsCount = cnt.length();
         final CharSequence[] vars = new CharSequence[fixedArgsCount];
         for (int j = fixedArgsCount - 1; j >= 0; --j) {
-            vars[j] = ctx.stackMapper.popValue();
+            vars[j] = ctx.stackMapper.popValue(ctx.out);
         }
 
 
         ctx.stackMapper.flush(ctx.out);
 
-        final Variable stringVar = ctx.stackMapper.pushA();
+        final CharSequence stringVar = ctx.stackMapper.pushA();
         ctx.out.append("\nvar ").append(stringVar).append(" = ");
 
         StringBuilder sep = new StringBuilder();

diff --git a/rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java b/rt/vm/src/main/java/org/apidesign/vm4brwsr/VM.java
@@ -224,7 +224,12 @@ private void generateBody(Appendable out, StringArray names) throws IOException
                 if (name == null) {
                     break;
                 }
-                InputStream is = resources.get(name + ".class");
+                InputStream is;
+                try {
+                    is = resources.get(name + ".class");
+                } catch (IOException noSuchResource) {
+                    is = null;
+                }
                 if (is == null) {
                     lazyReference(out, name);
                     skipClass.add(name);
@@ -235,7 +240,7 @@ private void generateBody(Appendable out, StringArray names) throws IOException
                     processed.add(name);
                     initCode.add(ic == null ? "" : ic);
                 } catch (RuntimeException ex) {
-                    throw new IOException("Error while compiling " + name + "\n", ex);
+                    throw new IOException("Error while compiling " + name + "\n" + ex.getClass().getName() + ": " + ex.getMessage(), ex);
                 }
             }
 

diff --git a/rt/vm/src/test/java/org/apidesign/vm4brwsr/BytesLoader.java b/rt/vm/src/test/java/org/apidesign/vm4brwsr/BytesLoader.java
@@ -46,7 +46,8 @@ static byte[] readClass(String name) throws IOException {
         if (u == null) {
             throw new IOException("Can't find " + name);
         }
-        try (InputStream is = u.openStream()) {
+        InputStream is = u.openStream();
+        try {
             byte[] arr;
             arr = new byte[is.available()];
             int offset = 0;
@@ -58,6 +59,8 @@ static byte[] readClass(String name) throws IOException {
                 offset += len;
             }
             return arr;
+        } finally {
+            is.close();
         }
     }
 

diff --git a/rt/vm/src/test/java/org/apidesign/vm4brwsr/Classes.java b/rt/vm/src/test/java/org/apidesign/vm4brwsr/Classes.java
@@ -281,7 +281,7 @@ public static Object reflectiveMethodCall(boolean direct, String mn) throws Exce
 
     public static int reflectiveSum(int a, int b) throws Exception {
         Method m = StaticMethod.class.getMethod("sum", int.class, int.class);
-        return (int) m.invoke(null, a, b);
+        return ((Number) m.invoke(null, a, b)).intValue();
     }
 
     private abstract class Application {

diff --git a/rt/vm/src/test/java/org/apidesign/vm4brwsr/Exceptions.java b/rt/vm/src/test/java/org/apidesign/vm4brwsr/Exceptions.java
@@ -71,7 +71,9 @@ public static String newInstance(String n) {
                 return ("CNFE:" + ex.getMessage()).toString();
             }
             return c.newInstance().getClass().getName();
-        } catch (InstantiationException | IllegalAccessException ex) {
+        } catch (InstantiationException  ex) {
+            return ex.getMessage();
+        } catch (IllegalAccessException ex) {
             return ex.getMessage();
         }
     }

diff --git a/rt/vm/src/test/java/org/apidesign/vm4brwsr/SizeOfAMethodTest.java b/rt/vm/src/test/java/org/apidesign/vm4brwsr/SizeOfAMethodTest.java
@@ -26,6 +26,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import static org.testng.Assert.*;
+import org.testng.SkipException;
 import org.testng.annotations.AfterClass;
 import org.testng.annotations.BeforeClass;
 import org.testng.annotations.Test;
@@ -37,7 +38,8 @@
 public class SizeOfAMethodTest {
     private static String code;
 
-    @Test public void sumXYShouldBeSmall() {
+    @Test
+    public void sumXYShouldBeSmall() {
         String s = code;
         int beg = s.indexOf("c.sum__III");
         int end = s.indexOf(".access", beg);
@@ -46,7 +48,8 @@ public class SizeOfAMethodTest {
         assertTrue(beg < end, "Found end of sum method in " + code);
 
         String method = s.substring(beg, end);
-
+
+        assumeNewStackMapper(method);
 
         assertEquals(method.indexOf("st"), -1, "There should be no stack operations:\n" + method);
     }
@@ -61,10 +64,13 @@ public class SizeOfAMethodTest {
 
         String method = s.substring(beg, end);
 
+        assumeNewStackMapper(method);
+
         assertEquals(method.indexOf("stA1"), -1, "No need for stA1 register:\n" + method);
     }
 
-    @Test public void deepConstructor() {
+    @Test 
+    public void deepConstructor() {
         String s = code;
         int beg = s.indexOf("c.intHolder__I");
         int end = s.indexOf(".access", beg);
@@ -73,11 +79,14 @@ public class SizeOfAMethodTest {
         assertTrue(beg < end, "Found end of intHolder method in " + code);
 
         String method = s.substring(beg, end);
+
+        assumeNewStackMapper(method);
 
         assertEquals(method.indexOf("stA3"), -1, "No need for stA3 register on second constructor:\n" + method);
     }
 
-    @Test public void emptyConstructorRequiresNoStack() {
+    @Test 
+    public void emptyConstructorRequiresNoStack() {
         String s = code;
         int beg = s.indexOf("CLS.cons__V");
         int end = s.indexOf(".access", beg);
@@ -87,12 +96,15 @@ public class SizeOfAMethodTest {
 
         String method = s.substring(beg, end);
         method = method.replace("constructor", "CNSTR");
+
+        assumeNewStackMapper(method);
 
         assertEquals(method.indexOf("st"), -1, "There should be no stack operations:\n" + method);
         assertEquals(method.indexOf("for"), -1, "There should be no for blocks:\n" + method);
     }
 
-    @Test public void dontGeneratePrimitiveFinalConstants() {
+    @Test
+    public void dontGeneratePrimitiveFinalConstants() {
         assertEquals(code.indexOf("MISSING_CONSTANT"), -1, "MISSING_CONSTANT field should not be generated");
     }
 
@@ -117,5 +129,12 @@ public InputStream get(String resource) throws IOException {
     public static void releaseTheCode() {
         code = null;
     }
+
+    private static void assumeNewStackMapper(String code) {
+        int stackArray = code.indexOf("var stack = [];");
+        if (stackArray >= 0) {
+            throw new SkipException("Skipping the text as code contains stack = []");
+        }
+    }
 
 }
diff --git a/rt/vm/src/test/java/org/apidesign/vm4brwsr/StackMapperTest.java b/rt/vm/src/test/java/org/apidesign/vm4brwsr/StackMapperTest.java
@@ -34,28 +34,28 @@ public StackMapperTest() {
     throws Exception {
         StringBuilder sb = new StringBuilder();
 
-        StackMapper smapper = new StackMapper();
+        AbstractStackMapper smapper = new StackMapper();
 
         smapper.assign(sb, VarType.INTEGER, "0");
 
         smapper.assign(sb, VarType.REFERENCE, "arr");
         smapper.assign(sb, VarType.INTEGER, "33");
         smapper.replace(sb, VarType.INTEGER, "@2[@1]", 
-            smapper.popI(), smapper.getA(0)
+            smapper.popI(sb), smapper.getA(sb, 0)
         );
 
         smapper.replace(sb, VarType.INTEGER, "(@1) + (@2)", 
-            smapper.getI(1), smapper.popI()
+            smapper.getI(sb, 1), smapper.popI(sb)
         );
 
         smapper.assign(sb, VarType.REFERENCE, "arr");
         smapper.assign(sb, VarType.INTEGER, "22");
         smapper.replace(sb, VarType.INTEGER, "@2[@1]", 
-            smapper.popI(), smapper.getA(0)
+            smapper.popI(sb), smapper.getA(sb, 0)
         );
 
         smapper.replace(sb, VarType.INTEGER, "(@1) + (@2)", 
-            smapper.getI(1), smapper.popI()
+            smapper.getI(sb, 1), smapper.popI(sb)
         );
 
         smapper.flush(sb);

diff --git a/rt/vm/src/test/java/org/apidesign/vm4brwsr/StringSample.java b/rt/vm/src/test/java/org/apidesign/vm4brwsr/StringSample.java
@@ -104,12 +104,10 @@ public static int countAB(String txt) {
     }
 
     public static int stringSwitch(String txt) {
-        switch (txt) {
-            case "jedna": return 1;
-            case "dve": return 2;
-            case "tri": return 3;
-            case "ctyri": return 4;
-        }
+        if ("jedna".equals(txt)) return 1;
+        if ("dve".equals(txt)) return 2;
+        if ("tri".equals(txt)) return 3;
+        if ("ctyri".equals(txt)) return 4;
         return -1;
     }
 

diff --git a/rt/vm/src/test/java/org/apidesign/vm4brwsr/StringTest.java b/rt/vm/src/test/java/org/apidesign/vm4brwsr/StringTest.java
@@ -85,13 +85,24 @@ public class StringTest {
         );
     }
 
-    @Test(timeOut=10000) public void toStringConcatenation() throws Exception {
+    @Test
+    public void toStringConcatenation1() throws Exception {
+        assertExec(
+            "Five executions should generate 5Hello World!",
+            StringSample.class, "toStringTest__Ljava_lang_String_2I",
+            "Hello World!1", 1
+        );
+    }
+
+    @Test
+    public void toStringConcatenation5() throws Exception {
         assertExec(
             "Five executions should generate 5Hello World!",
             StringSample.class, "toStringTest__Ljava_lang_String_2I",
             "Hello World!5", 5
         );
     }
+
     @Test public void toStringConcatenationJava() throws Exception {
         assertEquals("Hello World!5", StringSample.toStringTest(5));
     }