Handle synthetic method parameters entries that don't have names

> If the value of the name_index item is zero, then this parameters element indicates a formal parameter with no name. https://docs.oracle.com/javase/specs/jvms/se20/html/jvms-4.html#jvms-4.7.24 PiperOrigin-RevId: 530356139
google · May 8, 2023 · 0f20345 · 0f20345
1 parent 672a1e0
commit 0f20345
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Showing 2 changed files with 17 additions and 8 deletions.
diff --git a/java/com/google/turbine/bytecode/ClassReader.java b/java/com/google/turbine/bytecode/ClassReader.java
@@ -226,9 +226,10 @@ private void readMethodParameters(
     int unusedLength = reader.u4();
     int numParameters = reader.u1();
     for (int i = 0; i < numParameters; i++) {
-      String name = constantPool.utf8(reader.u2());
+      int nameIndex = reader.u2();
+      String name = nameIndex == 0 ? null : constantPool.utf8(nameIndex);
       int access = reader.u2();
-      if ((access & (TurbineFlag.ACC_SYNTHETIC | TurbineFlag.ACC_MANDATED)) != 0) {
+      if (name == null || (access & (TurbineFlag.ACC_SYNTHETIC | TurbineFlag.ACC_MANDATED)) != 0) {
         // ExecutableElement#getParameters doesn't expect synthetic or mandated
         // parameters
         continue;

diff --git a/javatests/com/google/turbine/bytecode/ClassReaderTest.java b/javatests/com/google/turbine/bytecode/ClassReaderTest.java
@@ -40,6 +40,7 @@
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.FieldVisitor;
 import org.objectweb.asm.Handle;
+import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.ModuleVisitor;
 import org.objectweb.asm.Opcodes;
 
@@ -57,12 +58,16 @@ public void methods() {
         null,
         "java/lang/Object",
         null);
-    cw.visitMethod(
-        Opcodes.ACC_PUBLIC,
-        "f",
-        "(Ljava/lang/String;)Ljava/lang/String;",
-        "<T:Ljava/lang/String;>(TT;)TT;",
-        null);
+    MethodVisitor mv =
+        cw.visitMethod(
+            Opcodes.ACC_PUBLIC,
+            "f",
+            "(Ljava/lang/String;)Ljava/lang/String;",
+            "<T:Ljava/lang/String;>(TT;)TT;",
+            null);
+    mv.visitParameter(null, 0); // skip synthetic parameters
+    mv.visitParameter("<no name>", Opcodes.ACC_SYNTHETIC); // skip synthetic parameters
+    mv.visitParameter("parameterName", 42);
     cw.visitMethod(
         Opcodes.ACC_PUBLIC | Opcodes.ACC_STATIC,
         "g",
@@ -92,6 +97,9 @@ public void methods() {
     assertThat(f.annotations()).isEmpty();
     assertThat(f.parameterAnnotations()).isEmpty();
     assertThat(f.defaultValue()).isNull();
+    assertThat(f.parameters()).hasSize(1);
+    assertThat(f.parameters().get(0).name()).isEqualTo("parameterName");
+    assertThat(f.parameters().get(0).access()).isEqualTo(42);
 
     ClassFile.MethodInfo g = classFile.methods().get(1);
     assertThat(g.access()).isEqualTo(TurbineFlag.ACC_PUBLIC | TurbineFlag.ACC_STATIC);