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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 "Value stored is never read" due to reference captured in lambda"
href="http://llvm.org/bugs/show_bug.cgi?id=22834">22834</a>
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<th>Summary</th>
<td>False "Value stored is never read" due to reference captured in lambda
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>3.5
</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>
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<th>Assignee</th>
<td>kremenek@apple.com
</td>
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<th>Reporter</th>
<td>atwyman@dropbox.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=14004" name="attach_14004" title="Runnable example">attachment 14004</a> <a href="attachment.cgi?id=14004&action=edit" title="Runnable example">[details]</a></span>
Runnable example
If a value is captured in a lambda, then modified later in the code, the
analyzer thinks the value is never used, and flags it as a dead store, even if
the lambda is run locally to use the value. Here's a simple example, where
f1() prints "0" rather than "1" as a result of the indicated line.
bool b = true;
auto f1 = [&b] () {
cout << b << endl;
};
b = false; // warning on this line
f1();
/ws/art_hack/ArtCppHack/ArtCppHack/main.cpp:12:5: warning: Value stored to 'b'
is never read
b = false;
^ ~~~~~
1 warning generated.
We're generally able to work around this by adding something like "(void)b;" to
make the variable appear to be used, but it would be nice not to have to.
I'm using the analyzer integrated in Xcode 6.1.1.</pre>
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