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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - reading a long double from a stream is out by a factor of 10"
href="http://llvm.org/bugs/show_bug.cgi?id=15751">15751</a>
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<th>Summary</th>
<td>reading a long double from a stream is out by a factor of 10
</td>
</tr>
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<th>Product</th>
<td>libc++
</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>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>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>All Bugs
</td>
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<th>Assignee</th>
<td>hhinnant@apple.com
</td>
</tr>
<tr>
<th>Reporter</th>
<td>john@johnmaddock.co.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This issue is causing most of the Boost.Math lib tests to fail, sample code is:
int main(int argc, char** argv)
{
std::stringstream ss;
long double r3;
ss << "304888344611713860501504000000";
ss >> r3;
std::cout << std::setprecision(std::numeric_limits<long
double>::max_digits10) << r3 << std::endl;
r3 = 304888344611713860501504000000.0L;
std::cout << std::setprecision(std::numeric_limits<long
double>::max_digits10) << r3 << std::endl;
return 0;
}
Which outputs:
3.04888344611713860494e+28
3.04888344611713860494e+29
Note how the value read from the stream is 10 times too small :-(
The issue still occurs if I append a ".0" to the input string.
Platform is Ubuntu Linux, latest clang and libc++ SVN Trunk. Same issue with
last release as well. GCC/libstdc++ and MSVC both handle this fine.</pre>
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</p>
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