Missing a local variable in Soot's Jimple representation - soot

Question

It seems that there is some internal optimization in soot to reuse local variables while transforming java byte code to Jimple. Therefore, in the Jimple representation, a local variable may be replaced by another local variable.
Now I want to disable the replacement and preserve all local variables in the source code, but how to do it?
For example, there are three local variables scanner, x, and y in the following method.
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
if (scanner.nextBoolean()) {
int x = scanner.nextInt();
System.out.println(x * x);
} else {
int y = scanner.nextInt();
System.out.println(y * y);
}
}
}
But in Jimple representation, the local variable y is missing. All the definition and usage of y is replaced by the local variable x.
//Jimple represenation with `-w -keep-line-number -p jb use-original-names:true`
public static void main(java.lang.String[])
{
java.lang.String[] args;
java.util.Scanner scanner, $stack3;
java.io.InputStream $stack4;
boolean $stack5;
int $stack7, $stack10, x;
java.io.PrintStream $stack8, $stack11;
args := #parameter0: java.lang.String[];
$stack3 = new java.util.Scanner;
$stack4 = <java.lang.System: java.io.InputStream in>;
specialinvoke $stack3.<java.util.Scanner: void <init>(java.io.InputStream)>($stack4);
scanner = $stack3;
$stack5 = virtualinvoke scanner.<java.util.Scanner: boolean nextBoolean()>();
if $stack5 == 0 goto label1;
x = virtualinvoke scanner.<java.util.Scanner: int nextInt()>();
$stack11 = <java.lang.System: java.io.PrintStream out>;
$stack10 = x * x;
virtualinvoke $stack11.<java.io.PrintStream: void println(int)>($stack10);
goto label2;
label1:
x = virtualinvoke scanner.<java.util.Scanner: int nextInt()>();
$stack8 = <java.lang.System: java.io.PrintStream out>;
$stack7 = x * x;
virtualinvoke $stack8.<java.io.PrintStream: void println(int)>($stack7);
label2:
return;
}
I have read the Soot command-line options and tried to disable some functions during Jimple Body Creation. Some options (e.g., jb.ulp, jb.a) can certainly influence the local variable in Jimple,
but none of them solve the missing local variable y problem.
//Jimple represenation with `-w -keep-line-number -p jb use-original-names:true -p jb.ulp enabled:false`
public static void main(java.lang.String[])
{
java.lang.String[] args;
java.util.Scanner scanner, $stack3;
java.io.InputStream $stack4;
boolean $stack5;
int $stack7, $stack10, x#1, x#2;
java.io.PrintStream $stack8, $stack11;
args := #parameter0: java.lang.String[];
$stack3 = new java.util.Scanner;
$stack4 = <java.lang.System: java.io.InputStream in>;
specialinvoke $stack3.<java.util.Scanner: void <init>(java.io.InputStream)>($stack4);
scanner = $stack3;
$stack5 = virtualinvoke scanner.<java.util.Scanner: boolean nextBoolean()>();
if $stack5 == 0 goto label1;
x#1 = virtualinvoke scanner.<java.util.Scanner: int nextInt()>();
$stack11 = <java.lang.System: java.io.PrintStream out>;
$stack10 = x#1 * x#1;
virtualinvoke $stack11.<java.io.PrintStream: void println(int)>($stack10);
goto label2;
label1:
x#2 = virtualinvoke scanner.<java.util.Scanner: int nextInt()>();
$stack8 = <java.lang.System: java.io.PrintStream out>;
$stack7 = x#2 * x#2;
virtualinvoke $stack8.<java.io.PrintStream: void println(int)>($stack7);
label2:
return;
}
======================
//Jimple represenation with `-w -keep-line-number -p jb use-original-names:true -p jb.a enabled:false`
public static void main(java.lang.String[])
{
java.lang.String[] args;
java.util.Scanner scanner, $stack3;
java.io.InputStream $stack4;
boolean $stack5;
int $stack6, $stack7, $stack9, $stack10, x;
java.io.PrintStream $stack8, $stack11;
args := #parameter0: java.lang.String[];
$stack3 = new java.util.Scanner;
$stack4 = <java.lang.System: java.io.InputStream in>;
specialinvoke $stack3.<java.util.Scanner: void <init>(java.io.InputStream)>($stack4);
scanner = $stack3;
$stack5 = virtualinvoke scanner.<java.util.Scanner: boolean nextBoolean()>();
if $stack5 == 0 goto label1;
$stack9 = virtualinvoke scanner.<java.util.Scanner: int nextInt()>();
x = $stack9;
$stack11 = <java.lang.System: java.io.PrintStream out>;
$stack10 = x * x;
virtualinvoke $stack11.<java.io.PrintStream: void println(int)>($stack10);
goto label2;
label1:
$stack6 = virtualinvoke scanner.<java.util.Scanner: int nextInt()>();
x = $stack6;
$stack8 = <java.lang.System: java.io.PrintStream out>;
$stack7 = x * x;
virtualinvoke $stack8.<java.io.PrintStream: void println(int)>($stack7);
label2:
return;
}
I also tried following parameters:
-p jb.cp-ule enabled:false, -p jb.dae enabled:false, -p jb.cp enabled:false, -p jb.lns enabled:false, -p jb.ule enabled:false, -p jb preserve-source-annotations:true
but they does not influence the defined local variables in Jimple.
Any suggestion for disabling the replacement and preserving all local variables in the source code?

Answer 1

Not sure if you are still interested in an answer to this question. We've found that Soot always optimizes the code while creating a Jimple body, regardless of the related command-line options. We have a fix for that in a specific fork (https://github.com/spgroup/soot), branch release-3.3.1.
Running soot with the option -p jb optimize:false solves this issue.