patch: javap does not show SourceDebugExtension properly

[Dmytro Sheyko]

Jonathan,

This bug does not manifest itself with exception. javap just prints

SourceDebugExtension: null

In a class file content of SDE attribute appears as UTF-8 string, where the first 4 bytes are 'S', 'M', 'A', 'P'. Existing code of SourceDebugExtension_attribute.getValue() uses readUTF and hence attempts to interpret the first two bytes (i.e. 'S' and 'M') as length of the string and then fails with EOFException. Then it catches this exception and returns null, which, in turn, appears in output.

As for sample class file, it's generated by Tomcat 7.0 runtime. I will send it later.

Regards,
Dmytro

> Date: Tue, 25 Jun 2013 12:01:32 -0700
> From: jonathan.gibbons at oracle.com
> To: compiler-dev at openjdk.java.net
> Subject: Re: patch: javap does not show SourceDebugExtension properly
> 
> Dmytro,
> 
> Thank you for your suggestion.  Can you provide more details on why the 
> existing code does not work. Presumably you get an exception -- what is 
> it?  Alternative, can you provide a sample class file for which the 
> existing code does not work, together with info on which version of 
> which compiler generated the class file?
> 
> I agree that the change to visitSourceDebugExtension is probably desirable.
> 
> -- Jon
> 
> 
> On 06/25/2013 11:32 AM, Dmytro Sheyko wrote:
> > Hello,
> >
> > I was trying to get SourceDebugExtension for compiled jsp class using javap (1.7.0_25, 1.8.0-ea-b91) and it printed something like:
> >
> >    SourceFile: "x_jsp.java"
> >    SourceDebugExtension: null
> >    minor version: 0
> >    major version: 50
> >
> > where expected output is following:
> >
> >    SourceFile: "x_jsp.java"
> >    SourceDebugExtension:
> >      SMAP
> >      x_jsp.java
> >      JSP
> >      *S JSP
> >      *F
> >      + 0 x.jsp
> >      x.jsp
> >      *L
> >      1,3:62
> >      4:65,4
> >      6,4:70
> >      9,4:74
> >      *E
> >    minor version: 0
> >    major version: 50
> >
> > Getting SourceDebugExtension using JDI works well (i.e. class file is correct).
> >
> > And I would like to propose a patch to fix this issue. Please review.
> >
> > diff -r b3458329d060 src/share/classes/com/sun/tools/classfile/SourceDebugExtension_attribute.java
> > --- a/src/share/classes/com/sun/tools/classfile/SourceDebugExtension_attribute.java    Mon Jun 24 14:27:32 2013 -0700
> > +++ b/src/share/classes/com/sun/tools/classfile/SourceDebugExtension_attribute.java    Tue Jun 25 20:22:06 2013 +0300
> > @@ -25,9 +25,8 @@
> >   
> >   package com.sun.tools.classfile;
> >   
> > -import java.io.ByteArrayInputStream;
> > -import java.io.DataInputStream;
> >   import java.io.IOException;
> > +import java.nio.charset.Charset;
> >   
> >   /**
> >    * See JVMS, section 4.8.15.
> > @@ -38,6 +37,8 @@
> >    *  deletion without notice.</b>
> >    */
> >   public class SourceDebugExtension_attribute extends Attribute {
> > +    private static final Charset UTF8 = Charset.forName("UTF-8");
> > +
> >       SourceDebugExtension_attribute(ClassReader cr, int name_index, int length) throws IOException {
> >           super(name_index, length);
> >           debug_extension = new byte[attribute_length];
> > @@ -55,12 +56,7 @@
> >       }
> >   
> >       public String getValue() {
> > -        DataInputStream d  = new DataInputStream(new ByteArrayInputStream(debug_extension));
> > -        try {
> > -            return d.readUTF();
> > -        } catch (IOException e) {
> > -            return null;
> > -        }
> > +        return new String(debug_extension, UTF8);
> >       }
> >   
> >       public <R, D> R accept(Visitor<R, D> visitor, D data) {
> > diff -r b3458329d060 src/share/classes/com/sun/tools/javap/AttributeWriter.java
> > --- a/src/share/classes/com/sun/tools/javap/AttributeWriter.java    Mon Jun 24 14:27:32 2013 -0700
> > +++ b/src/share/classes/com/sun/tools/javap/AttributeWriter.java    Tue Jun 25 20:22:06 2013 +0300
> > @@ -511,7 +511,10 @@
> >       }
> >   
> >       public Void visitSourceDebugExtension(SourceDebugExtension_attribute attr, Void ignore) {
> > -        println("SourceDebugExtension: " + attr.getValue());
> > +        println("SourceDebugExtension:");
> > +        indent(+1);
> > +        print(attr.getValue());
> > +        indent(-1);
> >           return null;
> >       }
> >   
> > Regards,
> > Dmytro 		 	   		
> 
 		 	   		  
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