Merge branch 'asm-fix/signature-writer/use-unsigned-arg-stack'

2 files changed, 35 insertions, 13 deletions

diff --git a/asm/src/main/java/org/objectweb/asm/signature/SignatureWriter.java b/asm/src/main/java/org/objectweb/asm/signature/SignatureWriter.java
index 2217a88a..df5f61d0 100644
--- a/asm/src/main/java/org/objectweb/asm/signature/SignatureWriter.java
+++ b/asm/src/main/java/org/objectweb/asm/signature/SignatureWriter.java
@@ -41,7 +41,7 @@ import org.objectweb.asm.Opcodes;
 public class SignatureWriter extends SignatureVisitor {
 
   /** The builder used to construct the visited signature. */
-  private final StringBuilder stringBuilder = new StringBuilder();
+  private final StringBuilder stringBuilder;
 
   /** Whether the visited signature contains formal type parameters. */
   private boolean hasFormals;
@@ -51,8 +51,9 @@ public class SignatureWriter extends SignatureVisitor {
 
   /**
    * The stack used to keep track of class types that have arguments. Each element of this stack is
-   * a boolean encoded in one bit. The top of the stack is the least significant bit. Pushing false
-   * = *2, pushing true = *2+1, popping = /2.
+   * a boolean encoded in one bit. The top of the stack is the least significant bit. The bottom of
+   * the stack is a sentinel element always equal to 1 (used to detect when the stack is full).
+   * Pushing false = {@code <<= 1}, pushing true = {@code '( <<= 1) | 1}, popping = {@code >>>= 1}.
    *
    * <p>Class type arguments must be surrounded with '&lt;' and '&gt;' and, because
    *
@@ -62,15 +63,20 @@ public class SignatureWriter extends SignatureVisitor {
    *       SignatureWriter instances),
    * </ol>
    *
-   * <p>we need a stack to properly balance these 'parentheses'. A new element is pushed on this
-   * stack for each new visited type, and popped when the visit of this type ends (either is
+   * <p>we need a stack to properly balance these angle brackets. A new element is pushed on this
+   * stack for each new visited type, and popped when the visit of this type ends (either in
    * visitEnd, or because visitInnerClassType is called).
    */
-  private int argumentStack;
+  private int argumentStack = 1;
 
   /** Constructs a new {@link SignatureWriter}. */
   public SignatureWriter() {
+    this(new StringBuilder());
+  }
+
+  private SignatureWriter(final StringBuilder stringBuilder) {
     super(/* latest api =*/ Opcodes.ASM9);
+    this.stringBuilder = stringBuilder;
   }
 
   // -----------------------------------------------------------------------------------------------
@@ -159,7 +165,7 @@ public class SignatureWriter extends SignatureVisitor {
     stringBuilder.append(name);
     // Pushes 'false' on the stack, meaning that this type does not have type arguments (as far as
     // we can tell at this point).
-    argumentStack *= 2;
+    argumentStack <<= 1;
   }
 
   @Override
@@ -169,7 +175,7 @@ public class SignatureWriter extends SignatureVisitor {
     stringBuilder.append(name);
     // Pushes 'false' on the stack, meaning that this type does not have type arguments (as far as
     // we can tell at this point).
-    argumentStack *= 2;
+    argumentStack <<= 1;
   }
 
   @Override
@@ -177,7 +183,7 @@ public class SignatureWriter extends SignatureVisitor {
     // If the top of the stack is 'false', this means we are visiting the first type argument of the
     // currently visited type. We therefore need to append a '<', and to replace the top stack
     // element with 'true' (meaning that the current type does have type arguments).
-    if (argumentStack % 2 == 0) {
+    if ((argumentStack & 1) == 0) {
       argumentStack |= 1;
       stringBuilder.append('<');
     }
@@ -189,14 +195,15 @@ public class SignatureWriter extends SignatureVisitor {
     // If the top of the stack is 'false', this means we are visiting the first type argument of the
     // currently visited type. We therefore need to append a '<', and to replace the top stack
     // element with 'true' (meaning that the current type does have type arguments).
-    if (argumentStack % 2 == 0) {
+    if ((argumentStack & 1) == 0) {
       argumentStack |= 1;
       stringBuilder.append('<');
     }
     if (wildcard != '=') {
       stringBuilder.append(wildcard);
     }
-    return this;
+    // If the stack is full, start a nested one by returning a new SignatureWriter.
+    return (argumentStack & (1 << 31)) == 0 ? this : new SignatureWriter(stringBuilder);
   }
 
   @Override
@@ -232,9 +239,9 @@ public class SignatureWriter extends SignatureVisitor {
     // If the top of the stack is 'true', this means that some type arguments have been visited for
     // the type whose visit is now ending. We therefore need to append a '>', and to pop one element
     // from the stack.
-    if (argumentStack % 2 == 1) {
+    if ((argumentStack & 1) == 1) {
       stringBuilder.append('>');
     }
-    argumentStack /= 2;
+    argumentStack >>>= 1;
   }
 }
diff --git a/asm/src/test/java/org/objectweb/asm/signature/SignaturesProviders.java b/asm/src/test/java/org/objectweb/asm/signature/SignaturesProviders.java
index ce6cf22a..a04d5801 100644
--- a/asm/src/test/java/org/objectweb/asm/signature/SignaturesProviders.java
+++ b/asm/src/test/java/org/objectweb/asm/signature/SignaturesProviders.java
@@ -32,6 +32,9 @@ public final class SignaturesProviders {
     assertFalse(CLASS_SIGNATURES.isEmpty());
     assertFalse(FIELD_SIGNATURES.isEmpty());
     assertFalse(METHOD_SIGNATURES.isEmpty());
+    for (int depth = 0; depth < 48; ++depth) {
+      METHOD_SIGNATURES.add(buildDeepSignature(new StringBuilder(), depth).toString());
+    }
   }
 
   private SignaturesProviders() {}
@@ -82,6 +85,18 @@ public final class SignaturesProviders {
         0);
   }
 
+  private static StringBuilder buildDeepSignature(final StringBuilder signature, final int depth) {
+    signature.append("LGeneric");
+    if (depth == 0) {
+      signature.append(';');
+    } else {
+      signature.append("<LOpen;");
+      buildDeepSignature(signature, depth - 1);
+      signature.append("LClose;>;");
+    }
+    return signature;
+  }
+
   static Stream<String> classSignatures() {
     return CLASS_SIGNATURES.stream();
   }