diff --git a/classlib/src/main/java/org/teavm/classlib/java/util/TDate.java b/classlib/src/main/java/org/teavm/classlib/java/util/TDate.java
index 561f86594..42dabe755 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/util/TDate.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/util/TDate.java
@@ -16,6 +16,7 @@
 package org.teavm.classlib.java.util;
 
 import java.util.TimeZone;
+import org.teavm.classlib.PlatformDetector;
 import org.teavm.classlib.java.lang.TComparable;
 import org.teavm.classlib.java.lang.TSystem;
 import org.teavm.jso.core.JSDate;
@@ -184,7 +185,11 @@ public class TDate implements TComparable<TDate> {
 
     @Override
     public String toString() {
-        return JSDate.create(value).stringValue();
+        if (PlatformDetector.isLowLevel()) {
+            return "";
+        } else {
+            return JSDate.create(value).stringValue();
+        }
     }
 
     @Deprecated
diff --git a/classlib/src/main/java/org/teavm/classlib/java/util/logging/TLogger.java b/classlib/src/main/java/org/teavm/classlib/java/util/logging/TLogger.java
index 1bf516650..a4b1b62c8 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/util/logging/TLogger.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/util/logging/TLogger.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.classlib.java.util.logging;
 
+import org.teavm.classlib.PlatformDetector;
 import org.teavm.classlib.java.lang.TInteger;
 import org.teavm.classlib.java.lang.TObject;
 import org.teavm.classlib.java.lang.TThrowable;
@@ -58,12 +59,19 @@ public class TLogger {
 
     public void log(TLogRecord record) {
         String message = format(record.getMessage(), record.getParameters());
-        if (record.getLevel().intValue() >= TLevel.SEVERE.intValue()) {
-            error(message);
-        } else if (record.getLevel().intValue() >= TLevel.WARNING.intValue()) {
-            warn(message);
+        if (PlatformDetector.isLowLevel()) {
+            System.out.print("[");
+            System.out.print(record.getLevel().getName());
+            System.out.print("] ");
+            System.out.println(message);
         } else {
-            infoImpl(message);
+            if (record.getLevel().intValue() >= TLevel.SEVERE.intValue()) {
+                error(message);
+            } else if (record.getLevel().intValue() >= TLevel.WARNING.intValue()) {
+                warn(message);
+            } else {
+                infoImpl(message);
+            }
         }
     }
 
diff --git a/core/src/main/java/org/teavm/backend/c/CTarget.java b/core/src/main/java/org/teavm/backend/c/CTarget.java
index c3de9c33c..9d8dcf0a0 100644
--- a/core/src/main/java/org/teavm/backend/c/CTarget.java
+++ b/core/src/main/java/org/teavm/backend/c/CTarget.java
@@ -63,6 +63,7 @@ import org.teavm.backend.c.intrinsic.PlatformIntrinsic;
 import org.teavm.backend.c.intrinsic.PlatformObjectIntrinsic;
 import org.teavm.backend.c.intrinsic.RuntimeClassIntrinsic;
 import org.teavm.backend.c.intrinsic.ShadowStackIntrinsic;
+import org.teavm.backend.c.intrinsic.StringsIntrinsic;
 import org.teavm.backend.c.intrinsic.StructureIntrinsic;
 import org.teavm.backend.lowlevel.dependency.ExceptionHandlingDependencyListener;
 import org.teavm.backend.lowlevel.transform.CoroutineTransformation;
@@ -195,6 +196,9 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
                 void.class)).use();
         dependencyAnalyzer.linkMethod(new MethodReference(ExceptionHandling.class, "throwNullPointerException",
                 void.class)).use();
+        dependencyAnalyzer.linkMethod(new MethodReference(NullPointerException.class, "<init>", void.class))
+                .propagate(0, NullPointerException.class.getName())
+                .use();
 
         dependencyAnalyzer.linkMethod(new MethodReference(ExceptionHandling.class, "catchException",
                 Throwable.class)).use();
@@ -287,6 +291,7 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
         intrinsics.add(new FiberIntrinsic());
         intrinsics.add(new LongIntrinsic());
         intrinsics.add(new IntegerIntrinsic());
+        intrinsics.add(new StringsIntrinsic());
 
         List<Generator> generators = new ArrayList<>();
         generators.add(new ArrayGenerator());
diff --git a/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java b/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
index 82902bff3..da210fe33 100644
--- a/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
+++ b/core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java
@@ -15,8 +15,17 @@
  */
 package org.teavm.backend.c.generate;
 
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.DoubleBuffer;
+import java.nio.FloatBuffer;
+import java.nio.IntBuffer;
+import java.nio.LongBuffer;
+import java.nio.ShortBuffer;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import org.teavm.ast.ArrayType;
 import org.teavm.ast.AssignmentStatement;
@@ -97,6 +106,8 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
     private static final MethodReference MONITOR_EXIT_SYNC = new MethodReference(Object.class, "monitorExitSync",
             Object.class, void.class);
 
+    private static final Map<String, String> BUFFER_TYPES = new HashMap<>();
+
     private GenerationContext context;
     private NameProvider names;
     private CodeWriter writer;
@@ -107,6 +118,16 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
     private boolean end;
     private boolean async;
 
+    static {
+        BUFFER_TYPES.put(ByteBuffer.class.getName(), "int8_t");
+        BUFFER_TYPES.put(ShortBuffer.class.getName(), "int16_t");
+        BUFFER_TYPES.put(CharBuffer.class.getName(), "char16_t");
+        BUFFER_TYPES.put(IntBuffer.class.getName(), "int32_t");
+        BUFFER_TYPES.put(LongBuffer.class.getName(), "int64_t");
+        BUFFER_TYPES.put(FloatBuffer.class.getName(), "float");
+        BUFFER_TYPES.put(DoubleBuffer.class.getName(), "double");
+    }
+
     public CodeGenerationVisitor(GenerationContext context, CodeWriter writer, Set<? super String> includes) {
         this.context = context;
         this.writer = writer;
@@ -469,7 +490,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         }
 
         for (int i = 0; i < expr.getArguments().size(); ++i) {
-            temporaries.add(allocTemporaryVariable(CVariableType.PTR));
+            temporaries.add(allocTemporaryVariable(parameterTypeForCall(method, i)));
         }
         boolean stringResult = method.getResultType().isObject(String.class);
 
@@ -489,6 +510,13 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                 writer.print("ARRAY_DATA(");
                 expr.getArguments().get(i).acceptVisitor(this);
                 writer.print(", ").printStrictType(((ValueType.Array) type).getItemType()).print(")");
+            } else if (isPrimitiveBuffer(type)) {
+                writer.print("ARRAY_DATA(FIELD(");
+                String typeName = ((ValueType.Object) type).getClassName();
+                expr.getArguments().get(i).acceptVisitor(this);
+                writer.print(", ").print(names.forClass(typeName)).print(", ")
+                        .print(names.forMemberField(new FieldReference(typeName, "array"))).print(")");
+                writer.print(", ").print(BUFFER_TYPES.get(typeName)).print(")");
             } else {
                 expr.getArguments().get(i).acceptVisitor(this);
             }
@@ -507,7 +535,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                     writer.print(", ");
                 }
                 writer.print(temporaries.get(i));
-                freeTemporaryVariable(CVariableType.PTR);
+                freeTemporaryVariable(parameterTypeForCall(method, i));
             }
             writer.print(")");
         } else if (method.parameterCount() > 0 || method.getResultType() == ValueType.VOID) {
@@ -534,6 +562,14 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         writer.print(")");
     }
 
+    private CVariableType parameterTypeForCall(MethodReader method, int index) {
+        if (method.hasModifier(ElementModifier.STATIC)) {
+            return typeToCType(method.parameterType(index));
+        } else {
+            return index == 0 ? CVariableType.PTR : typeToCType(method.parameterType(index - 1));
+        }
+    }
+
     private static boolean isPrimitiveArray(ValueType type) {
         if (!(type instanceof ValueType.Array)) {
             return false;
@@ -542,15 +578,28 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         return ((ValueType.Array) type).getItemType() instanceof ValueType.Primitive;
     }
 
+    private static boolean isPrimitiveBuffer(ValueType type) {
+        if (!(type instanceof ValueType.Object)) {
+            return false;
+        }
+        return BUFFER_TYPES.containsKey(((ValueType.Object) type).getClassName());
+    }
+
     private boolean isWrappedNativeCall(MethodReader method) {
         if (!method.hasModifier(ElementModifier.NATIVE)) {
             return false;
         }
+        if (method.getAnnotations().get(Variable.class.getName()) != null) {
+            return true;
+        }
         for (ValueType type : method.getParameterTypes()) {
-            if (type.isObject(String.class)) {
+            if (type.isObject(String.class) || isPrimitiveArray(type) || isPrimitiveBuffer(type)) {
                 return true;
             }
         }
+        if (method.getResultType().isObject(String.class)) {
+            return true;
+        }
         return false;
     }
 
diff --git a/core/src/main/resources/org/teavm/backend/c/runtime.c b/core/src/main/resources/org/teavm/backend/c/runtime.c
index c95c03aba..a44e42a12 100644
--- a/core/src/main/resources/org/teavm/backend/c/runtime.c
+++ b/core/src/main/resources/org/teavm/backend/c/runtime.c
@@ -305,6 +305,7 @@ static int32_t teavm_timeZoneOffset() {
 }
 
 static char* teavm_stringToC(void*);
+static JavaString* teavm_cToString(char*);
 static inline void teavm_free(void*);
 
 static inline int64_t teavm_reinterpretDoubleToLong(double v) {