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Bug 198157

Summary:	[compiler][null][correlation] False positive on potential null pointer access warning when re-using a condition
Product:	[Eclipse Project] JDT	Reporter:	Daniel Aborg <eclipse.daniel.aborg>
Component:	Core	Assignee:	JDT-Core-Inbox <jdt-core-inbox>
Status:	CLOSED DUPLICATE	QA Contact:
Severity:	enhancement
Priority:	P5	CC:	max.gilead, stephan.herrmann
Version:	3.3	Keywords:	helpwanted
Target Milestone:	4.7 M1
Hardware:	PC
OS:	Windows XP
Whiteboard:

Description Daniel Aborg

2007-07-27 15:29:07 EDT

Build ID: I20070621-1340

Steps To Reproduce:

The following code produces a potential null pointer warning:

final String s;
if (condition) {
	s = "Hello";
} else { 
	s = null;
}

if (condition) {
	s.indexOf(1);
}

As does this code:

String s = null;
if (condition) {
	s = "Hello";
}

if (condition) {
	s.indexOf(1);
}

Comment 1 Daniel Aborg

2007-07-27 15:31:09 EDT

The warning disappears if you replace the if with a conditional, but that is not always possible (e.g. the if branches contain multiple statements).

Comment 2 Maxime Daniel

2007-07-28 06:21:53 EDT

This is a case of variables correlation. We currently have no plans to address that class of null analysis issues. Lowering the priority accordingly.

Comment 3 Max Gilead

2010-02-18 14:09:58 EST

I believe this is the same issue so I'll post a bit another test case here:

void test(final Object a, final Object b) {
    if (a == null && b == null) {
        return;
    }
    if (a == null && b != null) {
        return;
    }
    System.out.println(a.hashCode()); // Potential null pointer access
}

Comment 4 Stephan Herrmann

2016-06-28 17:17:24 EDT

Bulk closing all compiler bugs tagged [null][correlation], because we have no plans to add such a feature: it would be a tremendous implementation effort, beyond our current man power, and may be impossible to achieve within the desired performance bounds.

If s.o. has a viable strategy or even implementation for such a feature, I'm all ears.

Comment 5 Jay Arthanareeswaran

2016-08-03 07:58:06 EDT

Verified for 4.7 M1.

Comment 6 Stephan Herrmann

2018-08-30 10:33:17 EDT

I created a new umbrella RFE outlining what would be needed to address this issue.

*** This bug has been marked as a duplicate of bug 538421 ***