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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW " title="NEW --- - false positive due to ignoring nonwritten value" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D23693&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=dRPfivqbqEhZHal5YWze9TR4v-wjDA0eWFMNM3HryWI&s=D_wJI8EXbQe3-mf9Mv0LpjTxd0vRvc0jASmeSqg5rNQ&e=">23693</a>
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<th>Summary</th>
<td>false positive due to ignoring nonwritten value
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>3.4
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Static Analyzer
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<th>Assignee</th>
<td>kremenek@apple.com
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<th>Reporter</th>
<td>rgerhards@hq.adiscon.com
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<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>Created <span class=""><a href="attachment.cgi?id=14403" name="attach_14403" title="Report">attachment 14403</a> <a href="attachment.cgi?id=14403&action=edit" title="Report">[details]</a></span>
Report
I have banged my head over this one for quite a while. I think it either is a
false positive ... or the construct is too complex for static analysis.
Have a look at the attached report. Keep an eye on variable
"expr->r->nodetype". Between points 2 and 7, it never is written. However, the
analyzer assumes in step 3 that it's value is 'A' but in step 6 it assumes it
has changed to not 'A'. The only place where it could potentially have been
written is in line 2285, as part of the function call. And, indeed, if I
comment out that line, the report goes away.
Note that evalStrArrayCmp() never writes the expr->r parameter. If I change the
prototype to explicitely make expt->r const, the warning goes away. So it looks
the static analyzer now unerstands that the value cannot change.
Question now: is this a bug or an inherant limit in static analysis?</pre>
</div>
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