Proguard fails to create output jar

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1

posted in this-SO-post:
I’m running proguard on a single class file but the output.jar file is not created.

$ javap -c java-8-classes/BinaryNode.class | sed -n "139,150p;151q"
  public int hashCode();
    Code:
       0: aload_0
       1: getfield      #2                  // Field _data:[B
       4: ifnonnull     11
       7: iconst_m1
       8: goto          16
      11: aload_0
      12: getfield      #2                  // Field _data:[B
      15: arraylength
      16: ireturn

So unless I’m mistaken(?) it seems that BinaryNode::hashCode only needs _data field.

$ javap -c java-8-classes/BinaryNode.class | sed -n "5,6p;7q"
  protected final byte[] _data;

So I edited my config.pro accordingly:

$ cat config.pro
-injars java-8-classes/BinaryNode.class
-outjars output.jar
-verbose
-keep class com.fasterxml.jackson.databind.node.BinaryNode
{
    protected final byte[] _data;
    public int hashCode();
}
-allowaccessmodification

When I run proguard, output jar does not get created:

$ java -jar ../proguard/lib/proguard.jar -dontwarn @config.pro
ProGuard, version 7.1.0-beta2
Reading input...
Reading program directory [/home/oren/Documents/java-8-classes/BinaryNode.class] (filtered) # <---- OK??
Initializing...
<...>
Preparing output jar [/home/oren/Documents/output.jar] (filtered) # <---- WHY ???
2

Hi @AliveBeef !

I’ve tried reproducing this: the problem is probably the package.

What package is BinaryNode class in? Is it still in the jackson package or is it in the root package?

Is there any warning on stderr like:

Warning: class [BinaryNode.class] unexpectedly contains class [com.fasterxml.jackson.databind.node.BinaryNode]
Warning: there were 1 classes in incorrectly named files.
...
Warning: the output jar is empty. Did you specify the proper '-keep' options?
...

If you instead, pass the jackson databind jar as input it works fine:

~/Downloads $ cat config.pro 
#-injars /home/james/Downloads/BinaryNode.class
-injars jackson-databind-2.12.2.jar
-outjars output.jar
-verbose
-keep class com.fasterxml.jackson.databind.node.BinaryNode
{
    protected final byte[] _data;
    public int hashCode();
}
-allowaccessmodification

~/Downloads $ unzip -l output.jar
Archive:  output.jar
  Length      Date    Time    Name
---------  ---------- -----   ----
    11614  2021-04-05 12:05   META-INF/MANIFEST.MF
    11358  2021-04-05 12:05   META-INF/LICENSE
      667  2021-04-05 12:05   META-INF/NOTICE
       78  2021-04-05 12:05   META-INF/maven/com.fasterxml.jackson.core/jackson-databind/pom.properties
    14785  2021-04-05 12:05   META-INF/maven/com.fasterxml.jackson.core/jackson-databind/pom.xml
       44  2021-04-05 12:05   META-INF/services/com.fasterxml.jackson.core.ObjectCodec
      163  2021-04-05 12:05   com/fasterxml/jackson/databind/a.class
      187  2021-04-05 12:05   com/fasterxml/jackson/databind/c.class
       84  2021-04-05 12:05   com/fasterxml/jackson/databind/b.class
      193  2021-04-05 12:05   com/fasterxml/jackson/databind/node/a.class
      366  2021-04-05 12:05   com/fasterxml/jackson/databind/node/BinaryNode.class
      173  2021-04-05 12:05   com/fasterxml/jackson/databind/node/b.class
3

Thanks for the answer James !

  • I reproduced the creation when using the whole jackson-databind jar.
  • I think I understand why my isolated class attempt failed
  • Proguard seems to need BinaryNode class’ super classes (?)
  • The one-letter minified classes are its ancestors in the inheritance tree:
    • BinaryNode → node/b → node/a → a → c → b (interface)
  • Is my understanding correct?