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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 --- - -Wunreachable-code warning involving templated local variable can't be suppressed with extra parentheses"
href="https://llvm.org/bugs/show_bug.cgi?id=28918">28918</a>
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<th>Summary</th>
<td>-Wunreachable-code warning involving templated local variable can't be suppressed with extra parentheses
</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>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Frontend
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>cpeterson@mozilla.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16922" name="attach_16922" title="test.cpp">attachment 16922</a> <a href="attachment.cgi?id=16922&action=edit" title="test.cpp">[details]</a></span>
test.cpp
-Wunreachable-code warning involving templated local variable can't be
suppressed with extra parentheses. I suppressed a -Wunreachable-code warning in
Firefox earlier this year [1] by adding extra parentheses, as suggested by
Xcode's clang on OS X. Unfortunately, this Firefox warning is back [2] because
clang 3.9 on Linux no longer recognizes the parentheses suppression.
Attached is a standalone test case that reproduces the insuppressible warning
even with Xcode's clang (Apple LLVM version 7.3.0 (clang-703.0.31)). So there
is a latent clang bug plus a regression that caused Firefox's
previously-suppressible warning to no longer be suppressible.
The warning looks like it might only happen when the boolean condition involves
an expression with a templated type. In the test case below, a templated local
variable gets copy-constructed to form an argument to a boolean
helper-function.
$ clang++ -Wunreachable-code test.cpp
test.cpp:23:5: warning: code will never be executed [-Wunreachable-code]
printf("Does clang warn about this code being unreachable?\n");
^~~~~~
1 warning generated.
[1] <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1223265">https://bugzilla.mozilla.org/show_bug.cgi?id=1223265</a>
[2] <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1291397">https://bugzilla.mozilla.org/show_bug.cgi?id=1291397</a></pre>
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