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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - llvm::sys::Memory not thread-safe"
href="http://llvm.org/bugs/show_bug.cgi?id=15749">15749</a>
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<th>Summary</th>
<td>llvm::sys::Memory not thread-safe
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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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>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Support Libraries
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>jim.kearney@oracle.com
</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>Memory::allocateMappedMemory() has a block-scope static that caches the size of
a page (in both Posix and Windows versions). When LLVM is built by a pre-C++11
compiler (note 1), multiple threads may race on examining and setting the
hidden boolean. In the case of MS Visual Studio this is disastrous because it
sets the flag before setting the value, which results in other threads using
the not-yet-set value.
static const size_t PageSize = Process::GetPageSize();
const size_t NumPages = (NumBytes+PageSize-1)/PageSize;
(1) C++11 says concurrent access must be serialized, previous Standards did
not.</pre>
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</p>
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