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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Undefined behavior in SmallVector implementation"
href="https://bugs.llvm.org/show_bug.cgi?id=36651">36651</a>
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<th>Summary</th>
<td>Undefined behavior in SmallVector implementation
</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>
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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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Core LLVM classes
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>tstellar@redhat.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Compiling with gcc 8 gives lots of warnings like:
/builddir/build/BUILD/llvm-6.0.0rc2.src/include/llvm/ADT/SmallVector.h:299:13:
warning: 'void* memcpy(void*, const void*, size_t)' writing to an object of
type 'struct std::pair<const llvm::MCSymbol*, const llvm::MCSymbol*>' with no
trivial copy-assignment; use copy-assignment or copy-initialization instead
[-Wclass-memaccess]
memcpy(Dest, I, (E - I) * sizeof(T));
This is undefined behavior, which can be fixed by using:
std::uninitialized_copy(), or maybe more optimally by first checking if T is
trivially copy-able. However, this code is only supposed to be called on POD
types, so there may be a bug somewhere else that is causing non-POD types to go
down this path.</pre>
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