<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 - raw_fd_ostream::write_impl hang due to an infinite loop with large output"
href="https://bugs.llvm.org/show_bug.cgi?id=37926">37926</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>raw_fd_ostream::write_impl hang due to an infinite loop with large output
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Windows NT
</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>Support Libraries
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>gbreynoo@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>The Windows implementation of raw_fd_ostream::write_impl calls Windows write:
write(int _FileHandle, void const* _Buf, unsigned int _MaxCharCount)
ChunkSize is a size_t type (unsigned 64bit on x64) used for the argument
_MaxCharCount (unsigned 32bit). This means there is an integral demotion and
only the least significant bytes are retained.
In the case of ChunkSize over 2^32 the least significant bytes are used and the
write performs successfully. Ptr and buffer size are then modified to reflect
this write, meaning the next ChunkSize will be a 64bit value with the least
significant bytes equalling 0.
When _MaxCharCount equals 0 Windows write fails, but as this is a recoverable
error raw_fd_ostream::write_impl reattempts the write. The program is now
caught in an infinite loop.
This was seen on Windows 10 using Visual Studio 2015, x64 build.</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>