Infinite recursion in ClassFile.foreachNestedClasses

[Daniel Klauer]

FindRealBugs currently crashes when analyzing most projects of the Qualitas Corpus, due to infinite recursion in ClassFile.foreachNestedClasses.

I have attached an example set of class files from the ant project. Corresponding source code: http://grepcode.com/file/repo1.maven.org/maven2/org.apache.ant/ant/1.8.4/org/apache/tools/ant/util/ResourceUtils.java#ResourceUtils

Output of ShowInnerClassesAttribute from OPAL's Demos project:

org/apache/tools/ant/util/ResourceUtils:
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$ResourceSelectorProvider,outerType=Some(org.apache.tools.ant.util.ResourceUtils),innerName=Some(ResourceSelectorProvider),accessFlags="public static [INTERFACE] abstract")
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$1,outerType=None,innerName=None,accessFlags="static")
org/apache/tools/ant/util/ResourceUtils$1:
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$1,outerType=None,innerName=None,accessFlags="static")
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$2,outerType=None,innerName=None,accessFlags="")
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$ResourceSelectorProvider,outerType=Some(org.apache.tools.ant.util.ResourceUtils),innerName=Some(ResourceSelectorProvider),accessFlags="public static [INTERFACE] abstract")
org/apache/tools/ant/util/ResourceUtils$2:
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$1,outerType=None,innerName=None,accessFlags="static")
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$2,outerType=None,innerName=None,accessFlags="")
org/apache/tools/ant/util/ResourceUtils$ResourceSelectorProvider:
    InnerClass(type=org.apache.tools.ant.util.ResourceUtils$ResourceSelectorProvider,outerType=Some(org.apache.tools.ant.util.ResourceUtils),innerName=Some(ResourceSelectorProvider),accessFlags="public static [INTERFACE] abstract")

Simplified:

ResourceUtils:
    ResourceUtils$ResourceSelectorProvider
    ResourceUtils$1
ResourceUtils$1:
    ResourceUtils$1
    ResourceUtils$2
    ResourceUtils$ResourceSelectorProvider
ResourceUtils$2:
    ResourceUtils$1
    ResourceUtils$2
ResourceUtils$ResourceSelectorProvider:
    ResourceUtils$ResourceSelectorProvider

The problem seems to be that the two inner classes ResourceUtils$1 and ResourceUtils$2 are referencing each other in their inner classes attributes. After looking at the source code, apparently they were produced by a construct such as:

class Test {
    Foo returnFoo() {
        return new Foo() {
            Bar returnBar() {
                return new Bar() {
                }
            }
        }
    }
}

I could not reproduce that in a test case though, because it will produce Test$1 and Test$1$1 as opposed to Test$1 and Test$2 like in the attached class files. (Perhaps they were produced by an older Java compiler which behaved differently.)

[Michael Eichberg]

FYI

I can reproduce the error - I'll take a look into this issue!

[Michael Eichberg]

After a very careful study it is obvious that this code violates the specification. (The class ResourceUtils$1 does not specify its outer class (it has no EnclosingMethod attribute)).

However, given that multiple projects fail, I'll look for a solution!

[Michael Eichberg]

I implemented an approach that solves this (instance of?) problem. It will be available with the next commit.

Anyway, I would highly appreciate it, if you could tell me if also works for the other projects in the qualitas corpus.

[Michael Eichberg]

fixes issue #45

→ <<cset 5a838f15fd27>>

[Daniel Klauer]

The issue has been solved for a lot of the projects from the Qualitas Corpus, but not all. I'll attach a set of class files from the batik 1.7 project which still trigger the infinite recursion problem.

[Michael Eichberg]

fixed issue #45

→ <<cset 53baf9c510b0>>

[Daniel Klauer]

Since the last change, there sometimes seems to be an infinite loop during foreachNestedClasses (although, no crash). I'll attach an affected set of class files.

[Michael Eichberg]

I wonder, if this issue will ever be finally resolved...

(in this case the problem was a named inner class of an anonymous outer class, where the anonymous outer class did not give any information about the named inner class....)

[Michael Eichberg]

fixed issue #45

added another test case

Signed-off-by: Michael Eichberg [e-mail]

→ <<cset d308ca813b56>>

[Daniel Klauer]

Another test case causing an infinite loop:

[Michael Eichberg]

fixed issue #45

→ <<cset 10e9811b7524>>

[Michael Eichberg]

Removing milestone: 0.8.0-M3 (automated comment)

[Michael Eichberg]

Removing version: 0.8.0 (automated comment)