What is signature class?

[Liang Guo <lguo@mail.eecis.udel.edu>]

I got an RuntimeException: cannot set active body for context or signature
class! when I construct my IPDG. 

it seems it got this exception when it try to call setActiveBody for
an abstract method. I remember the beta 3 constructed an empty body for
the abstract method, so it can work on. 


Exception in thread "main" java.lang.RuntimeException: cannot set active
body for context or signature class!
        at soot.SootMethod.setActiveBody(SootMethod.java, Compiled Code)
        at edu.udel.cis.compiler.graph.IPDG.<init>(IPDG.java, Compiled Code)
        at testIPDG.main(testIPDG.java, Compiled Code)

Liang
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