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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - False -Wunsequenced positive when combining comma and logical or"
href="https://bugs.llvm.org/show_bug.cgi?id=40137">40137</a>
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<th>Summary</th>
<td>False -Wunsequenced positive when combining comma and logical or
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>tony.wasserka@gmx.de
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<pre>Combining the comma operator with || seems to trigger false positives for
-Wunsequenced quite easily, see <a href="https://godbolt.org/z/azvBIZ">https://godbolt.org/z/azvBIZ</a> for an example.
Both , and || should sequence their operands, so the warning is unjustified in
this case.
Example code:
int idx = 0;
bool result = ((idx++, false) || (idx++, false));
( NB: This problem in particular shows up when trying to use fold expressions
to emulate if-elseif cascades via short-circuiting of ||, e.g. "((idx++,
are_we_done_yet(idx)) || ...)". )</pre>
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