<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Fold expression using comma gives unnecessary warning"
href="https://bugs.llvm.org/show_bug.cgi?id=45779">45779</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Fold expression using comma gives unnecessary warning
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>C++17
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>pkeir@outlook.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=23435" name="attach_23435" title="The file containing the code described.">attachment 23435</a> <a href="attachment.cgi?id=23435&action=edit" title="The file containing the code described.">[details]</a></span>
The file containing the code described.
Compiling the attached C++17 file (code also below) produces two warnings,
indicating that the result of the fold expression is unused. The result is
used.
template <typename ...Ts>
auto last(Ts ...xs) { return (xs , ...); }
int main(int argc, char *argv[])
{
int a = 0, b = 1, c = 2;
return last(a,b,c);
}
The warning messages are:
clang++ -std=c++17 comma-fold.cpp
comma-fold.cpp:2:31: warning: expression result unused [-Wunused-value]
auto last(Ts ...xs) { return (xs , ...); }
^~
comma-fold.cpp:7:10: note: in instantiation of function template specialization
'last<int, int, int>' requested here
return last(a,b,c);
^
comma-fold.cpp:2:31: warning: expression result unused [-Wunused-value]
auto last(Ts ...xs) { return (xs , ...); }
^~
2 warnings generated.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>