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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - quiet_NaN returns negative NaN"
href="http://llvm.org/bugs/show_bug.cgi?id=16666">16666</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>quiet_NaN returns negative NaN
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>3.2
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Headers
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>breese@stofanet.dk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>std::numeric_limits<T>::quiet_NaN() sets the sign bit on the NaN value for
float and double. I expect it to clear the sign bit.
This sign bit can cause incompatibility problems for serialization of IEEE 754
floating-point numbers to binary streams (e.g. for network protocols.) I
currently use std::abs(std::numeric_limits<T>::quiet_NaN()) as a workaround.
The following program demostrates the problem (I have verified that the problem
is not in std::cout). The same program produces the correct results when
compiled with g++.
#include <limits>
#include <iostream>
int main()
{
std::cout << std::numeric_limits<float>::quiet_NaN() << std::endl;
std::cout << std::numeric_limits<double>::quiet_NaN() << std::endl;
return 0;
}
PS: This bug is related to 15054, which also shows the incorrectly set sign bit
in its output.</pre>
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</p>
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