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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - static analyser reports null dereference when it clearly cannot happen"
href="http://llvm.org/bugs/show_bug.cgi?id=15679">15679</a>
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<th>Summary</th>
<td>static analyser reports null dereference when it clearly cannot happen
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<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>
</tr>
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<th>Assignee</th>
<td>kremenek@apple.com
</td>
</tr>
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<th>Reporter</th>
<td>gryzman@gmail.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>Created <span class=""><a href="attachment.cgi?id=10291" name="attach_10291" title="formatting.c from postgresql project">attachment 10291</a> <a href="attachment.cgi?id=10291&action=edit" title="formatting.c from postgresql project">[details]</a></span>
formatting.c from postgresql project
checker-272 on mac
fe-lobj.c from postgresql got flagged (attaching the result file and source
file).
But it clearly is visible in the same source file, that the condition could
never work out ! Clearly clang is unable to figure it out, and throws in loads
of false positives.
In short this looks like so:
void some_funct(struct f *foo)
{
if (foo==null || foo->bar==0)
{
if (initialise_f(foo) < 0)
return;
}
// this gets flagged as dereference of null pointer if foo is null
do_something(foo->bar);
}
int initialise_f(struct f* foo)
{
if (!foo)
{
return -1'
}
// ....
}
so in the example above (and attached code, look at function lo_tell64 and
lo_initialise) - this condition (dereference of null pointer) cannot happen.
Yet clang insists it does. After dozens of reports like that - and wasted time
on my pard - I decided to bug it here.</pre>
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