C: generate '#line' preprocessor directive

core/src/main/java/org/teavm/backend/c/CTarget.java

@@ -144,6 +144,7 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
     private Characteristics characteristics;
     private Set<MethodReference> asyncMethods;
     private boolean incremental;
+    private boolean lineNumbersGenerated;
     private StringPool stringPool;
 
     public CTarget() {
@@ -162,6 +163,10 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
         this.incremental = incremental;
     }
 
+    public void setLineNumbersGenerated(boolean lineNumbersGenerated) {
+        this.lineNumbersGenerated = lineNumbersGenerated;
+    }
+
     @Override
     public List<ClassHolderTransformer> getTransformers() {
         List<ClassHolderTransformer> transformers = new ArrayList<>();
@@ -332,8 +337,8 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
                 controller.getDependencyInfo(), stringPool, nameProvider, controller.getDiagnostics(), classes,
                 intrinsics, generators, asyncMethods::contains, buildTarget, incremental);
 
-        BufferedCodeWriter runtimeWriter = new BufferedCodeWriter();
+        BufferedCodeWriter runtimeWriter = new BufferedCodeWriter(false);
-        BufferedCodeWriter runtimeHeaderWriter = new BufferedCodeWriter();
+        BufferedCodeWriter runtimeHeaderWriter = new BufferedCodeWriter(false);
         emitResource(runtimeWriter, "runtime.c");
 
         runtimeHeaderWriter.println("#pragma once");
@@ -393,8 +398,8 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
         classGenerator.prepare(classes);
 
         for (String className : classNames) {
-            BufferedCodeWriter writer = new BufferedCodeWriter();
+            BufferedCodeWriter writer = new BufferedCodeWriter(lineNumbersGenerated);
-            BufferedCodeWriter headerWriter = new BufferedCodeWriter();
+            BufferedCodeWriter headerWriter = new BufferedCodeWriter(false);
             ClassHolder cls = classes.get(className);
             if (cls != null) {
                 classGenerator.generateClass(writer, headerWriter, cls);
@@ -408,8 +413,8 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
             if (type instanceof ValueType.Object) {
                 continue;
             }
-            BufferedCodeWriter writer = new BufferedCodeWriter();
+            BufferedCodeWriter writer = new BufferedCodeWriter(false);
-            BufferedCodeWriter headerWriter = new BufferedCodeWriter();
+            BufferedCodeWriter headerWriter = new BufferedCodeWriter(false);
             classGenerator.generateType(writer, headerWriter, type);
             String name = ClassGenerator.fileName(type);
             OutputFileUtil.write(writer, name + ".c", buildTarget);
@@ -451,8 +456,8 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
 
     private void generateCallSites(BuildTarget buildTarget, GenerationContext context,
             Collection<? extends String> classNames) throws IOException {
-        BufferedCodeWriter writer = new BufferedCodeWriter();
+        BufferedCodeWriter writer = new BufferedCodeWriter(false);
-        BufferedCodeWriter headerWriter = new BufferedCodeWriter();
+        BufferedCodeWriter headerWriter = new BufferedCodeWriter(false);
 
         IncludeManager includes = new SimpleIncludeManager(writer);
         includes.init("callsites.c");
@@ -491,8 +496,8 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
     }
 
     private void generateStrings(BuildTarget buildTarget, StringPool stringPool) throws IOException {
-        BufferedCodeWriter writer = new BufferedCodeWriter();
+        BufferedCodeWriter writer = new BufferedCodeWriter(false);
-        BufferedCodeWriter headerWriter = new BufferedCodeWriter();
+        BufferedCodeWriter headerWriter = new BufferedCodeWriter(false);
 
         headerWriter.println("#pragma once");
         headerWriter.println("#include \"runtime.h\"");
@@ -588,7 +593,7 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
 
     private void generateMainFile(GenerationContext context, ListableClassHolderSource classes,
             List<? extends ValueType> types, BuildTarget buildTarget) throws IOException {
-        BufferedCodeWriter writer = new BufferedCodeWriter();
+        BufferedCodeWriter writer = new BufferedCodeWriter(false);
         IncludeManager includes = new SimpleIncludeManager(writer);
         includes.init("main.c");
         includes.includePath("runtime.h");
@@ -601,7 +606,7 @@ public class CTarget implements TeaVMTarget, TeaVMCHost {
 
     private void generateAllFile(ListableClassHolderSource classes, List<? extends ValueType> types,
             BuildTarget buildTarget) throws IOException {
-        BufferedCodeWriter writer = new BufferedCodeWriter();
+        BufferedCodeWriter writer = new BufferedCodeWriter(false);
         IncludeManager includes = new SimpleIncludeManager(writer);
         includes.init("all.c");
         includes.includePath("runtime.c");

core/src/main/java/org/teavm/backend/c/generate/BufferedCodeWriter.java

@@ -18,18 +18,24 @@ package org.teavm.backend.c.generate;
 import java.io.PrintWriter;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 public class BufferedCodeWriter extends CodeWriter {
     private List<Fragment> fragments = new ArrayList<>();
     private int currentIndent;
     private int lastIndent;
     private StringBuilder buffer = new StringBuilder();
+    private boolean lineNumbersEmitted;
+    private String lastFileName;
+    private int lastLineNumber;
+    private boolean locationDirty;
 
-    public BufferedCodeWriter() {
+    public BufferedCodeWriter(boolean lineNumbersEmitted) {
+        this.lineNumbersEmitted = lineNumbersEmitted;
     }
 
-    public void writeTo(PrintWriter writer) {
+    public void writeTo(PrintWriter writer, String fileName) {
-        WriterWithContext writerWithContext = new WriterWithContext(writer);
+        WriterWithContext writerWithContext = new WriterWithContext(writer, fileName);
         for (Fragment fragment : fragments) {
             fragment.writeTo(writerWithContext);
         }
@@ -38,8 +44,12 @@ public class BufferedCodeWriter extends CodeWriter {
     @Override
     public CodeWriter fragment() {
         flush();
-        BufferedCodeWriter innerWriter = new BufferedCodeWriter();
+        BufferedCodeWriter innerWriter = new BufferedCodeWriter(lineNumbersEmitted);
+        innerWriter.lastFileName = lastFileName;
+        innerWriter.lastLineNumber = lastLineNumber;
+        innerWriter.locationDirty = locationDirty;
         fragments.add(new InnerWriterFragment(innerWriter.fragments));
+        locationDirty = true;
         return innerWriter;
     }
 
@@ -49,6 +59,9 @@ public class BufferedCodeWriter extends CodeWriter {
         buffer.setLength(0);
         lastIndent = currentIndent;
         currentIndent = 0;
+        if (lineNumbersEmitted) {
+            lastLineNumber++;
+        }
     }
 
     @Override
@@ -65,37 +78,123 @@ public class BufferedCodeWriter extends CodeWriter {
         }
     }
 
+    @Override
+    public void source(String fileName, int lineNumber) {
+        if (!lineNumbersEmitted) {
+            return;
+        }
+
+        if (!Objects.equals(lastFileName, fileName) || lastLineNumber != lineNumber || locationDirty) {
+            flush();
+            fragments.add(new SourceFragment(fileName, lineNumber));
+            lastFileName = fileName;
+            lastLineNumber = lineNumber;
+            locationDirty = false;
+        }
+    }
+
+    @Override
+    public void nosource() {
+        source(null, 0);
+    }
+
     @Override
     public void flush() {
+        if (buffer.length() > 0 || lastIndent != 0 || currentIndent != 0) {
             fragments.add(new SimpleFragment(false, lastIndent, buffer.toString()));
             lastIndent = currentIndent;
             currentIndent = 0;
             buffer.setLength(0);
         }
+    }
 
     static class WriterWithContext {
         PrintWriter writer;
         boolean isNewLine = true;
         int indentLevel;
+        String initialFileName;
+        String fileName;
+        int lineNumber;
+        int absLineNumber = 1;
+        String pendingFileName;
+        int pendingLineNumber = -1;
 
-        WriterWithContext(PrintWriter writer) {
+        WriterWithContext(PrintWriter writer, String fileName) {
             this.writer = writer;
+            this.fileName = fileName;
+            initialFileName = fileName;
+            lineNumber = 1;
         }
 
         void append(String text) {
-            if (isNewLine) {
+            if (text.isEmpty()) {
-                for (int i = 0; i < indentLevel; ++i) {
+                return;
-                    writer.print("    ");
             }
+            if (isNewLine) {
+                if (pendingFileName != null || pendingLineNumber >= 0) {
+                    printLineDirective(pendingFileName, pendingLineNumber);
+                    pendingLineNumber = -1;
+                    pendingFileName = null;
+                }
+                printIndent();
                 isNewLine = false;
             }
             writer.print(text);
         }
 
+        private void printLineDirective(String fileName, int lineNumber) {
+            if (Objects.equals(this.fileName, fileName) && lineNumber == this.lineNumber) {
+                return;
+            }
+
+            printIndent();
+            writer.print("#line ");
+            if (Objects.equals(fileName, initialFileName)) {
+                lineNumber = absLineNumber + 1;
+            }
+            writer.print(lineNumber);
+            if (!Objects.equals(fileName, this.fileName)) {
+                writer.print(" \"");
+                escape(writer, fileName);
+                writer.print("\"");
+            }
+            writer.println();
+            absLineNumber++;
+            this.fileName = fileName;
+            this.lineNumber = lineNumber;
+        }
+
         void newLine() {
+            lineNumber++;
+            absLineNumber++;
             writer.println();
             isNewLine = true;
         }
+
+        private void printIndent() {
+            for (int i = 0; i < indentLevel; ++i) {
+                writer.print("    ");
+            }
+        }
+
+        void source(String fileName, int lineNumber) {
+            if (fileName == null) {
+                fileName = initialFileName;
+                lineNumber = absLineNumber;
+            }
+            if (!Objects.equals(this.fileName, fileName) || this.lineNumber != lineNumber) {
+                if (isNewLine) {
+                    pendingFileName = fileName;
+                    pendingLineNumber = lineNumber;
+                } else {
+                    this.lineNumber++;
+                    absLineNumber++;
+                    writer.println();
+                    printLineDirective(fileName, lineNumber);
+                    isNewLine = true;
+                }
+            }
+        }
     }
 
     static abstract class Fragment {
@@ -123,6 +222,62 @@ public class BufferedCodeWriter extends CodeWriter {
         }
     }
 
+    static class SourceFragment extends Fragment {
+        private String fileName;
+        private int lineNumber;
+
+        SourceFragment(String fileName, int lineNumber) {
+            this.fileName = fileName;
+            this.lineNumber = lineNumber;
+        }
+
+        @Override
+        void writeTo(WriterWithContext writer) {
+            writer.source(fileName, lineNumber);
+        }
+    }
+
+    private static void escape(PrintWriter writer, String string) {
+        int chunkSize = 256;
+        for (int i = 0; i < string.length(); i += chunkSize) {
+            int last = Math.min(i + chunkSize, string.length());
+
+            for (int j = i; j < last; ++j) {
+                char c = string.charAt(j);
+                switch (c) {
+                    case '\\':
+                        writer.print("\\\\");
+                        break;
+                    case '"':
+                        writer.print("\\\"");
+                        break;
+                    case '\r':
+                        writer.print("\\r");
+                        break;
+                    case '\n':
+                        writer.print("\\n");
+                        break;
+                    case '\t':
+                        writer.print("\\t");
+                        break;
+                    default:
+                        if (c < 32) {
+                            writer.print("\\0" + Character.forDigit(c >> 3, 8) + Character.forDigit(c & 0x7, 8));
+                        } else if (c > 127) {
+                            writer.print("\\u"
+                                    + Character.forDigit(c >> 12, 16)
+                                    + Character.forDigit((c >> 8) & 15, 16)
+                                    + Character.forDigit((c >> 4) & 15, 16)
+                                    + Character.forDigit(c & 15, 16));
+                        } else {
+                            writer.print(c);
+                        }
+                        break;
+                }
+            }
+        }
+    }
+
     static class InnerWriterFragment extends Fragment {
         List<Fragment> fragments;
 

core/src/main/java/org/teavm/backend/c/generate/CodeGenerationVisitor.java

@@ -22,7 +22,9 @@ import java.nio.FloatBuffer;
 import java.nio.IntBuffer;
 import java.nio.LongBuffer;
 import java.nio.ShortBuffer;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
+import java.util.Deque;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -78,6 +80,7 @@ import org.teavm.model.ElementModifier;
 import org.teavm.model.FieldReference;
 import org.teavm.model.MethodReader;
 import org.teavm.model.MethodReference;
+import org.teavm.model.TextLocation;
 import org.teavm.model.ValueType;
 import org.teavm.model.classes.VirtualTable;
 import org.teavm.runtime.Allocator;
@@ -116,6 +119,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
     private IncludeManager includes;
     private boolean end;
     private boolean async;
+    private final Deque<LocationStackEntry> locationStack = new ArrayDeque<>();
 
     static {
         BUFFER_TYPES.put(ByteBuffer.class.getName(), "int8_t");
@@ -148,6 +152,8 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
     @Override
     public void visit(BinaryExpr expr) {
+        pushLocation(expr.getLocation());
+        try {
             switch (expr.getOperation()) {
                 case COMPARE:
                     writer.print("teavm_compare_");
@@ -275,10 +281,14 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
             writer.print(" ").print(op).print(" ");
             expr.getSecondOperand().acceptVisitor(this);
             writer.print(")");
+        } finally {
+            popLocation(expr.getLocation());
+        }
     }
 
     @Override
     public void visit(UnaryExpr expr) {
+        pushLocation(expr.getLocation());
         switch (expr.getOperation()) {
             case NOT:
                 writer.print("(");
@@ -316,10 +326,12 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                 writer.print(")");
                 break;
         }
+        popLocation(expr.getLocation());
     }
 
     @Override
     public void visit(ConditionalExpr expr) {
+        pushLocation(expr.getLocation());
         writer.print("(");
         expr.getCondition().acceptVisitor(this);
         writer.print(" ? ");
@@ -327,34 +339,43 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         writer.print(" : ");
         expr.getAlternative().acceptVisitor(this);
         writer.print(")");
+        popLocation(expr.getLocation());
     }
 
     @Override
     public void visit(ConstantExpr expr) {
+        pushLocation(expr.getLocation());
         CodeGeneratorUtil.writeValue(writer, context, includes, expr.getValue());
+        popLocation(expr.getLocation());
     }
 
     @Override
     public void visit(VariableExpr expr) {
+        pushLocation(expr.getLocation());
         if (expr.getIndex() == 0) {
             writer.print("teavm_this_");
         } else {
             writer.print("teavm_local_" + expr.getIndex());
         }
+        popLocation(expr.getLocation());
     }
 
     @Override
     public void visit(SubscriptExpr expr) {
+        pushLocation(expr.getLocation());
         writer.print("TEAVM_ARRAY_AT(");
         expr.getArray().acceptVisitor(this);
         writer.print(", ").print(getArrayType(expr.getType())).print(", ");
         expr.getIndex().acceptVisitor(this);
         writer.print(")");
+        popLocation(expr.getLocation());
     }
 
     @Override
     public void visit(UnwrapArrayExpr expr) {
+        pushLocation(expr.getLocation());
         expr.getArray().acceptVisitor(this);
+        popLocation(expr.getLocation());
     }
 
     private static String getArrayType(ArrayType type) {
@@ -393,10 +414,13 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
         Intrinsic intrinsic = context.getIntrinsic(expr.getMethod());
         if (intrinsic != null) {
+            pushLocation(expr.getLocation());
             intrinsic.apply(intrinsicContext, expr);
+            popLocation(expr.getLocation());
             return;
         }
 
+        pushLocation(expr.getLocation());
         switch (expr.getType()) {
             case CONSTRUCTOR: {
                 String receiver = allocTemporaryVariable(CVariableType.PTR);
@@ -482,6 +506,8 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                 break;
             }
         }
+
+        popLocation(expr.getLocation());
     }
 
     private void generateWrappedNativeCall(MethodReader method, InvocationExpr expr) {
@@ -647,6 +673,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
     public void visit(QualificationExpr expr) {
         FieldReference field = expr.getField();
         if (isMonitorField(field)) {
+            pushLocation(expr.getLocation());
             String tmp = allocTemporaryVariable(CVariableType.INT);
             writer.print("(" + tmp + " = TEAVM_FIELD(");
             expr.getQualified().acceptVisitor(this);
@@ -654,9 +681,11 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
             writer.print(", ").print(names.forClass(field.getClassName()) + ", "
                     + names.forMemberField(field) + ")");
             writer.print(", TEAVM_UNPACK_MONITOR(" + tmp + "))");
+            popLocation(expr.getLocation());
             return;
         }
 
+        pushLocation(expr.getLocation());
         includes.includeClass(field.getClassName());
         if (expr.getQualified() != null) {
             writer.print("TEAVM_FIELD(");
@@ -665,6 +694,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         } else {
             writer.print(names.forStaticField(field));
         }
+        popLocation(expr.getLocation());
     }
 
     private boolean isMonitorField(FieldReference field) {
@@ -673,9 +703,11 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
     @Override
     public void visit(NewExpr expr) {
+        pushLocation(expr.getLocation());
         includes.includeClass(expr.getConstructedClass());
         includes.includeClass(ALLOC_METHOD.getClassName());
         allocObject(expr.getConstructedClass());
+        popLocation(expr.getLocation());
     }
 
     private void allocObject(String className) {
@@ -686,6 +718,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
     @Override
     public void visit(NewArrayExpr expr) {
+        pushLocation(expr.getLocation());
         ValueType type = ValueType.arrayOf(expr.getType());
         writer.print(names.forMethod(ALLOC_ARRAY_METHOD)).print("(&")
                 .print(names.forClassInstance(type)).print(", ");
@@ -693,6 +726,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         includes.includeType(type);
         expr.getLength().acceptVisitor(this);
         writer.print(")");
+        popLocation(expr.getLocation());
     }
 
     @Override
@@ -714,10 +748,12 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
     @Override
     public void visit(InstanceOfExpr expr) {
+        pushLocation(expr.getLocation());
         writer.print("teavm_instanceof(");
         expr.getExpr().acceptVisitor(this);
         includes.includeType(expr.getType());
         writer.print(", ").print(names.forSupertypeFunction(expr.getType())).print(")");
+        popLocation(expr.getLocation());
     }
 
     @Override
@@ -730,14 +766,17 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                 return;
             }
         }
+        pushLocation(expr.getLocation());
         writer.print("teavm_checkcast(");
         expr.getValue().acceptVisitor(this);
         includes.includeType(expr.getTarget());
         writer.print(", ").print(names.forSupertypeFunction(expr.getTarget())).print(")");
+        popLocation(expr.getLocation());
     }
 
     @Override
     public void visit(PrimitiveCastExpr expr) {
+        pushLocation(expr.getLocation());
         writer.print("((");
         switch (expr.getTarget()) {
             case INT:
@@ -756,10 +795,12 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         writer.print(") ");
         expr.getValue().acceptVisitor(this);
         writer.print(")");
+        popLocation(expr.getLocation());
     }
 
     @Override
     public void visit(AssignmentStatement statement) {
+        pushLocation(statement.getLocation());
         if (statement.getLeftValue() != null) {
             if (statement.getLeftValue() instanceof QualificationExpr) {
                 QualificationExpr qualification = (QualificationExpr) statement.getLeftValue();
@@ -772,6 +813,7 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
                             + names.forMemberField(field) + ") = TEAVM_PACK_MONITOR(");
                     statement.getRightValue().acceptVisitor(this);
                     writer.println(");");
+                    popLocation(statement.getLocation());
                     return;
                 }
             }
@@ -785,6 +827,8 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         if (statement.isAsync()) {
             emitSuspendChecker();
         }
+
+        popLocation(statement.getLocation());
     }
 
     @Override
@@ -809,9 +853,11 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
     @Override
     public void visit(ConditionalStatement statement) {
         while (true) {
+            pushLocation(statement.getCondition().getLocation());
             writer.print("if (");
             statement.getCondition().acceptVisitor(this);
             writer.println(") {").indent();
+            popLocation(statement.getCondition().getLocation());
 
             visitMany(statement.getConsequent());
             writer.outdent().print("}");
@@ -836,9 +882,11 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
     @Override
     public void visit(SwitchStatement statement) {
+        pushLocation(statement.getValue().getLocation());
         writer.print("switch (");
         statement.getValue().acceptVisitor(this);
         writer.print(") {").println().indent();
+        popLocation(statement.getValue().getLocation());
 
         for (SwitchClause clause : statement.getClauses()) {
             for (int condition : clause.getConditions()) {
@@ -906,44 +954,54 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
     @Override
     public void visit(BreakStatement statement) {
+        pushLocation(statement.getLocation());
         if (statement.getTarget() == null || statement.getTarget().getId() == null) {
             writer.println("break;");
         } else {
             writer.println("goto teavm_label_" + statement.getTarget().getId() + ";");
         }
+        popLocation(statement.getLocation());
     }
 
     @Override
     public void visit(ContinueStatement statement) {
+        pushLocation(statement.getLocation());
         if (statement.getTarget() == null || statement.getTarget().getId() == null) {
             writer.println("continue;");
         } else {
             writer.println("goto teavm_cnt_" + statement.getTarget().getId() + ";");
         }
+        popLocation(statement.getLocation());
     }
 
     @Override
     public void visit(ReturnStatement statement) {
+        pushLocation(statement.getLocation());
         writer.print("return");
         if (statement.getResult() != null) {
             writer.print(" ");
             statement.getResult().acceptVisitor(this);
         }
         writer.println(";");
+        popLocation(statement.getLocation());
     }
 
     @Override
     public void visit(ThrowStatement statement) {
+        pushLocation(statement.getLocation());
         includes.includeClass(THROW_EXCEPTION_METHOD.getClassName());
         writer.print(names.forMethod(THROW_EXCEPTION_METHOD)).print("(");
         statement.getException().acceptVisitor(this);
         writer.println(");");
+        popLocation(statement.getLocation());
     }
 
     @Override
     public void visit(InitClassStatement statement) {
+        pushLocation(statement.getLocation());
         includes.includeClass(statement.getClassName());
         writer.println(names.forClassInitializer(statement.getClassName()) + "();");
+        popLocation(statement.getLocation());
     }
 
     @Override
@@ -956,18 +1014,22 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
 
     @Override
     public void visit(MonitorEnterStatement statement) {
+        pushLocation(statement.getLocation());
         includes.includeClass("java.lang.Object");
         writer.print(names.forMethod(async ? MONITOR_ENTER : MONITOR_ENTER_SYNC)).print("(");
         statement.getObjectRef().acceptVisitor(this);
         writer.println(");");
+        popLocation(statement.getLocation());
     }
 
     @Override
     public void visit(MonitorExitStatement statement) {
+        pushLocation(statement.getLocation());
         includes.includeClass("java.lang.Object");
         writer.print(names.forMethod(async ? MONITOR_EXIT : MONITOR_EXIT_SYNC)).print("(");
         statement.getObjectRef().acceptVisitor(this);
         writer.println(");");
+        popLocation(statement.getLocation());
     }
 
     public void emitSuspendChecker() {
@@ -1043,4 +1105,46 @@ public class CodeGenerationVisitor implements ExprVisitor, StatementVisitor {
         }
         return CVariableType.PTR;
     }
+
+    private void pushLocation(TextLocation location) {
+        if (location == null) {
+            return;
+        }
+        LocationStackEntry prevEntry = locationStack.peek();
+        if (prevEntry == null || !location.equals(prevEntry.location)) {
+            if (location.getFileName() == null) {
+                writer.nosource();
+            } else {
+                writer.source(location.getFileName(), location.getLine());
+            }
+        }
+        locationStack.push(new LocationStackEntry(location));
+    }
+
+    private void popLocation(TextLocation location) {
+        if (location == null) {
+            return;
+        }
+        LocationStackEntry prevEntry = locationStack.pop();
+        LocationStackEntry entry = locationStack.peek();
+        if (entry != null) {
+            if (!entry.location.equals(prevEntry.location)) {
+                if (entry.location.getFileName() == null) {
+                    writer.nosource();
+                } else {
+                    writer.source(entry.location.getFileName(), entry.location.getLine());
+                }
+            }
+        } else {
+            writer.nosource();
+        }
+    }
+
+    static class LocationStackEntry {
+        final TextLocation location;
+
+        LocationStackEntry(TextLocation location) {
+            this.location = location;
+        }
+    }
 }

core/src/main/java/org/teavm/backend/c/generate/CodeWriter.java

@@ -137,4 +137,8 @@ public abstract class CodeWriter {
     protected abstract void indentBy(int amount);
 
     public abstract void flush();
+
+    public abstract void source(String fileName, int lineNumber);
+
+    public abstract void nosource();
 }

core/src/main/java/org/teavm/backend/c/generate/GeneratorContextImpl.java

@@ -92,12 +92,12 @@ class GeneratorContextImpl implements GeneratorContext {
 
     @Override
     public FileGenerator createSourceFile(String path) {
-        return createFile(new BufferedCodeWriter(), path);
+        return createFile(new BufferedCodeWriter(false), path);
     }
 
     @Override
     public FileGenerator createHeaderFile(String path) {
-        BufferedCodeWriter writer = new BufferedCodeWriter();
+        BufferedCodeWriter writer = new BufferedCodeWriter(false);
         writer.println("#pragma once");
         return createFile(writer, path);
     }

core/src/main/java/org/teavm/backend/c/generate/OutputFileUtil.java

@@ -28,7 +28,7 @@ public final class OutputFileUtil {
     public static void write(BufferedCodeWriter code, String name, BuildTarget buildTarget) throws IOException {
         try (PrintWriter writer = new PrintWriter(new OutputStreamWriter(
                 buildTarget.createResource(name), StandardCharsets.UTF_8))) {
-            code.writeTo(writer);
+            code.writeTo(writer, name);
         }
     }
 }

tools/c-incremental/src/main/java/org/teavm/tooling/c/incremental/IncrementalCBuilder.java

@@ -64,6 +64,7 @@ public class IncrementalCBuilder {
     private String mainClass;
     private String[] classPath;
     private int minHeapSize = 32;
+    private boolean lineNumbersGenerated;
     private String targetPath;
     private String externalTool;
     private String externalToolWorkingDir;
@@ -107,6 +108,10 @@ public class IncrementalCBuilder {
         this.minHeapSize = minHeapSize;
     }
 
+    public void setLineNumbersGenerated(boolean lineNumbersGenerated) {
+        this.lineNumbersGenerated = lineNumbersGenerated;
+    }
+
     public void setTargetPath(String targetPath) {
         this.targetPath = targetPath;
     }
@@ -316,6 +321,7 @@ public class IncrementalCBuilder {
 
         cTarget.setIncremental(true);
         cTarget.setMinHeapSize(minHeapSize * 1024 * 1024);
+        cTarget.setLineNumbersGenerated(lineNumbersGenerated);
         vm.setOptimizationLevel(TeaVMOptimizationLevel.SIMPLE);
         vm.setCacheStatus(classSource);
         vm.addVirtualMethods(m -> true);

tools/cli/src/main/java/org/teavm/cli/TeaVMCBuilderRunner.java

@@ -52,6 +52,10 @@ public class TeaVMCBuilderRunner {
                 .withDescription("display more messages on server log")
                 .withLongOpt("verbose")
                 .create('v'));
+        options.addOption(OptionBuilder
+                .withDescription("generate debugger-friendly code")
+                .withLongOpt("debug")
+                .create('g'));
         options.addOption(OptionBuilder
                 .withLongOpt("min-heap")
                 .withArgName("size")
@@ -103,6 +107,7 @@ public class TeaVMCBuilderRunner {
         parseExternalTool();
 
         builder.setLog(new ConsoleTeaVMToolLog(commandLine.hasOption('v')));
+        builder.setLineNumbersGenerated(commandLine.hasOption('g'));
 
         String[] args = commandLine.getArgs();
         if (args.length != 1) {

tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java

@@ -321,6 +321,7 @@ public class TeaVMTool {
     private CTarget prepareCTarget() {
         cTarget = new CTarget();
         cTarget.setMinHeapSize(minHeapSize);
+        cTarget.setLineNumbersGenerated(debugInformationGenerated);
         return cTarget;
     }