4 files changed, 29 insertions, 8 deletions
diff --git a/asm/src/main/java/org/objectweb/asm/ClassReader.java b/asm/src/main/java/org/objectweb/asm/ClassReader.java
index 7f0e4e72..2cfef457 100644
--- a/asm/src/main/java/org/objectweb/asm/ClassReader.java
+++ b/asm/src/main/java/org/objectweb/asm/ClassReader.java
@@ -194,7 +194,7 @@ public class ClassReader {
     this.b = classFileBuffer;
     // Check the class' major_version. This field is after the magic and minor_version fields, which
     // use 4 and 2 bytes respectively.
-    if (checkClassVersion && readShort(classFileOffset + 6) > Opcodes.V20) {
+    if (checkClassVersion && readShort(classFileOffset + 6) > Opcodes.V21) {
       throw new IllegalArgumentException(
           "Unsupported class file major version " + readShort(classFileOffset + 6));
     }
@@ -2050,6 +2050,7 @@ public class ClassReader {
     currentOffset = bytecodeStartOffset;
     while (currentOffset < bytecodeEndOffset) {
       final int currentBytecodeOffset = currentOffset - bytecodeStartOffset;
+      readBytecodeInstructionOffset(currentBytecodeOffset);
 
       // Visit the label and the line number(s) for this bytecode offset, if any.
       Label currentLabel = labels[currentBytecodeOffset];
@@ -2666,6 +2667,20 @@ public class ClassReader {
   }
 
   /**
+   * Handles the bytecode offset of the next instruction to be visited in {@link
+   * #accept(ClassVisitor,int)}. This method is called just before the instruction and before its
+   * associated label and stack map frame, if any. The default implementation of this method does
+   * nothing. Subclasses can override this method to store the argument in a mutable field, for
+   * instance, so that {@link MethodVisitor} instances can get the bytecode offset of each visited
+   * instruction (if so, the usual concurrency issues related to mutable data should be addressed).
+   *
+   * @param bytecodeOffset the bytecode offset of the next instruction to be visited.
+   */
+  protected void readBytecodeInstructionOffset(final int bytecodeOffset) {
+    // Do nothing by default.
+  }
+
+  /**
    * Returns the label corresponding to the given bytecode offset. The default implementation of
    * this method creates a label for the given offset if it has not been already created.
    *
diff --git a/asm/src/main/java/org/objectweb/asm/Frame.java b/asm/src/main/java/org/objectweb/asm/Frame.java
index 07f256e5..89195006 100644
--- a/asm/src/main/java/org/objectweb/asm/Frame.java
+++ b/asm/src/main/java/org/objectweb/asm/Frame.java
@@ -367,11 +367,12 @@ class Frame {
             typeValue = REFERENCE_KIND | symbolTable.addType(internalName);
             break;
           default:
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException(
+                "Invalid descriptor fragment: " + buffer.substring(elementDescriptorOffset));
         }
         return ((elementDescriptorOffset - offset) << DIM_SHIFT) | typeValue;
       default:
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("Invalid descriptor: " + buffer.substring(offset));
     }
   }
 
diff --git a/asm/src/main/java/org/objectweb/asm/Label.java b/asm/src/main/java/org/objectweb/asm/Label.java
index 926f719e..4bcf7c56 100644
--- a/asm/src/main/java/org/objectweb/asm/Label.java
+++ b/asm/src/main/java/org/objectweb/asm/Label.java
@@ -81,6 +81,9 @@ public class Label {
   /** A flag indicating that the basic block corresponding to a label is the end of a subroutine. */
   static final int FLAG_SUBROUTINE_END = 64;
 
+  /** A flag indicating that this label has at least one associated line number. */
+  static final int FLAG_LINE_NUMBER = 128;
+
   /**
    * The number of elements to add to the {@link #otherLineNumbers} array when it needs to be
    * resized to store a new source line number.
@@ -145,9 +148,9 @@ public class Label {
   short flags;
 
   /**
-   * The source line number corresponding to this label, or 0. If there are several source line
-   * numbers corresponding to this label, the first one is stored in this field, and the remaining
-   * ones are stored in {@link #otherLineNumbers}.
+   * The source line number corresponding to this label, if {@link #FLAG_LINE_NUMBER} is set. If
+   * there are several source line numbers corresponding to this label, the first one is stored in
+   * this field, and the remaining ones are stored in {@link #otherLineNumbers}.
    */
   private short lineNumber;
 
@@ -332,7 +335,8 @@ public class Label {
    * @param lineNumber a source line number (which should be strictly positive).
    */
   final void addLineNumber(final int lineNumber) {
-    if (this.lineNumber == 0) {
+    if ((flags & FLAG_LINE_NUMBER) == 0) {
+      flags |= FLAG_LINE_NUMBER;
       this.lineNumber = (short) lineNumber;
     } else {
       if (otherLineNumbers == null) {
@@ -356,7 +360,7 @@ public class Label {
    */
   final void accept(final MethodVisitor methodVisitor, final boolean visitLineNumbers) {
     methodVisitor.visitLabel(this);
-    if (visitLineNumbers && lineNumber != 0) {
+    if (visitLineNumbers && (flags & FLAG_LINE_NUMBER) != 0) {
       methodVisitor.visitLineNumber(lineNumber & 0xFFFF, this);
       if (otherLineNumbers != null) {
         for (int i = 1; i <= otherLineNumbers[0]; ++i) {
diff --git a/asm/src/main/java/org/objectweb/asm/Opcodes.java b/asm/src/main/java/org/objectweb/asm/Opcodes.java
index 4a85a445..7202784f 100644
--- a/asm/src/main/java/org/objectweb/asm/Opcodes.java
+++ b/asm/src/main/java/org/objectweb/asm/Opcodes.java
@@ -286,6 +286,7 @@ public interface Opcodes {
   int V18 = 0 << 16 | 62;
   int V19 = 0 << 16 | 63;
   int V20 = 0 << 16 | 64;
+  int V21 = 0 << 16 | 65;
 
   /**
    * Version flag indicating that the class is using 'preview' features.