<html>
<head>
<base href="http://llvm.org/bugs/" />
</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 --- - Noisy warnings about const-attributed functions used in decltype"
href="http://llvm.org/bugs/show_bug.cgi?id=18571">18571</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Noisy warnings about const-attributed functions used in decltype
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>All
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</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++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>akim.demaille@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>It is very handy to use "decltype" to perform a snifae dispatch, as in this
example:
__attribute__((const))
bool bar()
{
return true;
}
template <typename T>
auto foo(T t) -> decltype(bar(), bool())
{
return true;
}
template <typename T>
bool foo(...)
{
return false;
}
int main()
{
return foo(23) != true;
}
Unfortunately, clang complains that the function I'm sfinaeing on, bar, is
const, and its result is ignored. The warning in itself makes sense, but not
here. In addition, it stutters.
akim@erebus /tmp $ clang++-mp-3.4 -std=c++11 sfinae.cc -Wall
sfinae.cc:8:27: warning: ignoring return value of function declared with const
attribute
[-Wunused-value]
auto foo(T t) -> decltype(bar(), bool())
^~~
sfinae.cc:8:27: warning: ignoring return value of function declared with const
attribute
[-Wunused-value]
auto foo(T t) -> decltype(bar(), bool())
^~~
2 warnings generated.
Likewise with 3.5.
$ clang++-mp-3.4 --version
clang version 3.4 (tags/RELEASE_34/final)
Target: x86_64-apple-darwin13.0.0
Thread model: posix
$ clang++-mp-3.5 --version
clang version 3.5 (trunk 198565)
Target: x86_64-apple-darwin13.0.0
Thread model: posix
Btw, I don't know if clang has something similar to gcc's
don't_ignore_the_return_value attribute, but there's probably the same issue.</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>