NPE when using java.lang.System.out/java.lang.System.err

[katyacyfra]

I run USVM on the the following function (Java Juliet test suite)

    public void bad() throws Throwable
    {
        byte data;

        /* POTENTIAL FLAW: Use the maximum size of the data type */
        data = Byte.MAX_VALUE;

        /* POTENTIAL FLAW: if data == Byte.MAX_VALUE, this will overflow */
        byte result = (byte)(data + 1);

        IO.writeLine("result: " + result);

    }

IO is implemented as follows.

There is an unexpected NPE during the USVM run.

Instruction: %0.println(arg$0)
Exception: JcException: Address: 0x15, type: java.lang.NullPointerException
Call stack (contains 2 frames):
	0: UCallStackFrame(method=(id:73)javajuliet.testcase.CWE190_Integer_Overflow.CWE190_Integer_Overflow__byte_max_add_01#bad(), returnSite=null)
	1: UCallStackFrame(method=(id:73)javajuliet.testcasesupport.IO#writeLine(java.lang.String), returnSite=javajuliet.testcasesupport.IO.writeLine(%7))

Assignments to null:

Instruction: java.lang.System.out = null
Call stack (contains 3 frames):
	0: UCallStackFrame(method=(id:73)javajuliet.testcase.CWE190_Integer_Overflow.CWE190_Integer_Overflow__byte_max_add_01#bad(), returnSite=null)
	1: UCallStackFrame(method=(id:73)javajuliet.testcasesupport.IO#writeLine(java.lang.String), returnSite=javajuliet.testcasesupport.IO.writeLine(%7))
	2: UCallStackFrame(method=(id:1)java.lang.System#<clinit>(), returnSite=%0 = java.lang.System.out)
================================================================
Instruction: java.lang.System.err = null
Call stack (contains 3 frames):
	0: UCallStackFrame(method=(id:73)javajuliet.testcase.CWE190_Integer_Overflow.CWE190_Integer_Overflow__byte_max_add_01#bad(), returnSite=null)
	1: UCallStackFrame(method=(id:73)javajuliet.testcasesupport.IO#writeLine(java.lang.String), returnSite=javajuliet.testcasesupport.IO.writeLine(%7))
	2: UCallStackFrame(method=(id:1)java.lang.System#<clinit>(), returnSite=%0 = java.lang.System.out)

And the final result is

20:08:04.945 |I| TestRunnerKt - 1 executions were found:
	JcTest(method=org.jacodb.impl.types.JcTypedMethodImpl@7131da33, before=JcParametersState(thisInstance=javajuliet.testcase.CWE190_Integer_Overflow.CWE190_Integer_Overflow__byte_max_add_01@6a278584, parameters=[]), after=JcParametersState(thisInstance=javajuliet.testcase.CWE190_Integer_Overflow.CWE190_Integer_Overflow__byte_max_add_01@28f90752, parameters=[]), result=Failure(java.lang.NullPointerException), coverage=JcCoverage(targetClassToCoverage={}))
Extracted values:
	[javajuliet.testcase.CWE190_Integer_Overflow.CWE190_Integer_Overflow__byte_max_add_01@6a278584, null]