MethodParameters class reading bug

[Liam Miller-Cushon]

I think I found a MethodParameters class reading bug that affects
annotation processing.

If MethodParameters attributes are not available parameter names are
inferred from the LVT, which uses two slots for doubles and longs. The
logic for skipping the extra slot is used even if the data was read from a
MethodParameters attribute, where the indices are always contiguous. So if
javac sees a parameter of type double or long it skips the next entry in
the MethodParameters table.

There's a simple fix:

diff -r 775a385c4af6
src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/ClassReader.java
---
a/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/ClassReader.java Thu
Dec 01 17:25:45 2016 -0800
+++
b/src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/ClassReader.java Thu
Dec 01 18:05:14 2016 -0800
@@ -2321,7 +2321,7 @@
                     ? parameterNameIndices[index] : 0);
             Name name = nameIdx == 0 ? names.empty : readName(nameIdx);
             paramNames = paramNames.prepend(name);
-            index += Code.width(t);
+            index += sawMethodParameters ? 1 : Code.width(t);
         }
         sym.savedParameterNames = paramNames.reverse();
     }

If my diagnosis sounds correct, I can clean up the patch and add a test.

Here's the full repro:

=== Lib.java
class Lib {
  void f(int a, long b, int c, int d) {}
}
=== Test.java
@Deprecated
class Test {}
=== ParameterProcessor.java
import java.util.Set;
import javax.annotation.processing.*;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.*;

@SupportedAnnotationTypes("*")
public class ParameterProcessor extends AbstractProcessor {
  @Override
  public boolean process(Set<? extends TypeElement> annotations,
RoundEnvironment roundEnv) {
    if (roundEnv.processingOver()) {
      return false;
    }
    TypeElement s = processingEnv.getElementUtils().getTypeElement("Lib");
    for (Element e : s.getEnclosedElements()) {
      if (e instanceof ExecutableElement) {
        for (VariableElement v : ((ExecutableElement) e).getParameters()) {
          System.err.printf("  %s %s\n", v.asType(), v.getSimpleName());
        }
      }
    }
    return false;
  }

  @Override
  public SourceVersion getSupportedSourceVersion() {
    return SourceVersion.latest();
  }
}

$ javac -parameters Lib.java
$ javac ParameterProcessor.java
$ javac -processor ParameterProcessor Test.java
  int a
  long b
  int d
  int arg3

Note that the third parameter is given the fourth parameter's name, and the
fourth parameter's name is unknown.

Thanks,

Liam
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