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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - False positive null pointer dereference with integer arithmetic"
href="http://llvm.org/bugs/show_bug.cgi?id=15855">15855</a>
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<th>Summary</th>
<td>False positive null pointer dereference with integer arithmetic
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>Macintosh
</td>
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<th>OS</th>
<td>MacOS X
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Static Analyzer
</td>
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<th>Assignee</th>
<td>kremenek@apple.com
</td>
</tr>
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<th>Reporter</th>
<td>bugzilla@jwwalker.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Overview:
I get a null pointer dereference warning that assumes a certain variable is
negative, when in fact one can easily deduce that the variable cannot be
negative.
Steps to reproduce:
Analyze this code:
-------------------------
static void Foo( int numFaces )
{
int* ptr = 0;
int absFaces;
if (numFaces > 0)
{
absFaces = numFaces;
}
else
{
absFaces = - numFaces;
}
if (absFaces < 0)
{
*ptr = 99;
}
}
-------------------------
Actual results:
"Dereference of null pointer (loaded from variable 'ptr')
'ptr' initialized to a null pointer value
Assuming 'numFaces' is <= 0
Assuming 'absFaces' is < 0"
Expected results:
No warnings, or maybe something saying that a line is unreachable.
Build date:
clang version 3.3 (trunk 180622)
Target: x86_64-apple-darwin11.4.2
Thread model: posix</pre>
</div>
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