Re: [Wala-wala] The use of DFSPathFinder on InterprocedureCFG

[Stephen F. <sj...@us...>]

I think the issue here is that the interprocedural CFG is not 
context-sensitive, so you are finding a path which is infeasible according 
to matched call-return pairs.  Specifically, you are finding a path in the 
IPCFG as follows:

1) sayHello calls say1
2) say1 calls println
3) println returns to the the 'else' branch of sayHello
4) sayHello calls say2

which is a path in the IPCFG, but infeasible since the call 2) is 
unmatched with the return 3).

SJF
------------------------------------------------------------------------
Stephen Fink
IBM T.J. Watson Research Center
sj...@us...
(914)784-7776




dongyu sun <sun...@ya...> 
10/27/2008 02:06 PM
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Subject
[Wala-wala] The use of DFSPathFinder on InterprocedureCFG







Hi,
 
       I am testing the DFSPathFinder on a InterprocedureCFG. I have a 
simple test program like following
 
public class HelloWorld { 
/** 
* @param args 
*/ 
public static void main(String[] args) { 
// TODO Auto-generated method stub 
HelloWorld h=new HelloWorld(); 
int i[]=new int[0]; 
int i2=i.length; 
int i3=i2; 
int i4=i3; 
i=null; 
h.sayHello("hi "); 
} 
public void sayHello(String greeting) 
{ 
TestClass testClas=new TestClass(); 
String test="test"; 
if(greeting =="") 
{ 
System.out.println(greeting); 
// testClas.method1_1(greeting); 
say1(); 
} 
else 
{ 
System.out.println(test); 
// testClas.method2(test); 
say2(); 
} 
} 
void say1() 
{ 
System.out.println("say1()"); 
} 
void say2() 
{ 
System.out.println("say2()"); 
} 
}
 
I first constructed the InterprocedureCFG from the CallGraph, then I use 
the DSFPathFinder on this InterprocedureCFG to try to find any path 
between the call to say1() to the call to say2(). 
In above helloWorld class, as this two function call are on the two 
branches of the if statement, I didn't expect any path to exist between 
them, but suprisingly I got one path like following when run the 
DSFPathFinder. 
 
the line with issBlk===>.. is produced by printing the toString() output 
of each of the 
BasicBlockInContext<ISSABasicBlock>
 
the line witn ins (...) is the toString() output of each instruction in 
each of the 
BasicBlockInContext<ISSABasicBlock>. the number in the bracket is the line 
number in the source code.
---------------------------------------------------------------------
 
issBlk===>BB[SSA:12..13]5 - 
simple.HelloWorld.sayHello(Ljava/lang/String;)V 
ins ( 29 ): invokevirtual < Application, Lsimple/HelloWorld, say1()V > 1 
@25 exception:13 
def Value String : v13 
use Value String : v1 
loca name ( this ) 
issBlk===>BB[SSA:-1..-2]0 - simple.HelloWorld.say1()V 
issBlk===>BB[SSA:0..2]1 - simple.HelloWorld.say1()V 
ins ( 43 ): 3 = getstatic < Application, Ljava/lang/System, out, 
<Application,Ljava/io/PrintStream> > 
def Value String : v3 
ins ( 43 ): invokevirtual < Application, Ljava/io/PrintStream, 
println(Ljava/lang/String;)V > 3,4 @5 exception:5 
def Value String : v5 
use Value String : v3 
use Value String : v4:#say1() 
issBlk===>BB[SSA:-1..-2]0 - 
java.io.PrintStream.println(Ljava/lang/String;)V 
issBlk===>BB[SSA:0..3]1 - java.io.PrintStream.println(Ljava/lang/String;)V 

issBlk===>BB[SSA:4..6]2 - java.io.PrintStream.println(Ljava/lang/String;)V 

issBlk===>BB[SSA:7..8]3 - java.io.PrintStream.println(Ljava/lang/String;)V 

issBlk===>BB[SSA:9..10]4 - 
java.io.PrintStream.println(Ljava/lang/String;)V 
issBlk===>BB[SSA:11..11]5 - 
java.io.PrintStream.println(Ljava/lang/String;)V 
issBlk===>BB[SSA:17..17]8 - 
java.io.PrintStream.println(Ljava/lang/String;)V 
issBlk===>BB[SSA:-1..-2]9 - 
java.io.PrintStream.println(Ljava/lang/String;)V 
issBlk===>BB[SSA:18..19]8 - 
simple.HelloWorld.sayHello(Ljava/lang/String;)V 
ins ( 35 ): invokevirtual < Application, Lsimple/HelloWorld, say2()V > 1 
@39 exception:10 
def Value String : v10 
use Value String : v1 
loca name ( this )
 
 
It seems that the path is from the call to say1() go into the function 
definition of say(), then come out and jump on to the call to say2().. Is 
this path right in a CFG?
 
thanks
dongyu
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