[Soot-list] How to track a String variable backward in Jimple?

[Steven Lee]

Hello everyone,

 

I'm trying to estimate a variable's value in Java, here are my Java code and
corresponding Jimple code:

 

Java:

    public static void main(String[] args) {

        String x, y;

        x = "hello, ";

        y = x + "world";

        x = y;

}

 

Jimple:

01> public static void main(java.lang.String[]){

02>     java.lang.String[] args;

03>     java.lang.String x, y, $r1;

04>     java.lang.StringBuilder $r0;

05>     args := @parameter0: java.lang.String[];

06>     x = "hello, ";

07>     $r0 = new java.lang.StringBuilder;

08>     $r1 = staticinvoke <java.lang.String: java.lang.String
valueOf(java.lang.Object)>(x);

09>     specialinvoke $r0.<java.lang.StringBuilder: void
<init>(java.lang.String)>($r1);

10>     $r0 = virtualinvoke $r0.<java.lang.StringBuilder:
java.lang.StringBuilder append(java.lang.String)>("world");

11>     y = virtualinvoke $r0.<java.lang.StringBuilder: java.lang.String
toString()>();

12>     x = y;

13>     return;

14> }

 

I want to use static analysis to find what is the value of variable "y"  at
line 12, so I used SimpleLocalDefs.getDefsOfAt() to find where "y" was
assigned, then I came to line 11 and found that I need to know the value of
$r0. The same way I arrived at line 10, however this time I called
SimpleLocalDefs.getDefsOfAt(), it returns line 07, where $r0 was
initialized, instead of line 09, where I thought the nearest place where $r0
was defined or changed.

 

I know this is because of Reaching-Definition Analysis's scheme. Then what
can I do to continue my work? I'm considering re-implement my own
Reaching-Definition Analysis with my demand, is that an acceptable approach?
And I want to know more about Jimple's String manipulation but failed to
find some complete and systematic document, do they exist?

 

Thanks in advance.

 

Steven Lee

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