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<body><span class="vcard"><a class="email" href="mailto:whitequark@whitequark.org" title="whitequark <whitequark@whitequark.org>"> <span class="fn">whitequark</span></a>
</span> changed
<a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED --- - clang emits memcpy for std::swap, which can introduce undefined behavior"
href="https://llvm.org/bugs/show_bug.cgi?id=27498">bug 27498</a>
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<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>RESOLVED
</td>
<td>REOPENED
</td>
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<td style="text-align:right;">Resolution</td>
<td>DUPLICATE
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<td>---
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<b><a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED --- - clang emits memcpy for std::swap, which can introduce undefined behavior"
href="https://llvm.org/bugs/show_bug.cgi?id=27498#c2">Comment # 2</a>
on <a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED --- - clang emits memcpy for std::swap, which can introduce undefined behavior"
href="https://llvm.org/bugs/show_bug.cgi?id=27498">bug 27498</a>
from <span class="vcard"><a class="email" href="mailto:whitequark@whitequark.org" title="whitequark <whitequark@whitequark.org>"> <span class="fn">whitequark</span></a>
</span></b>
<pre>Sorry but I am reopening this. Specifically because the generated IR violates
LLVM's own invariats! To quote LangRef for @llvm.memcpy: "The ‘llvm.memcpy.*‘
intrinsics copy a block of memory from the source location to the destination
location, which are not allowed to overlap."
<a href="http://llvm.org/docs/LangRef.html#id407">http://llvm.org/docs/LangRef.html#id407</a>
It might be that the fix is adjusting the contract of @llvm.memcpy--it is not
my call. But I would say that the current self-contradictory behavior is
indefensible.</pre>
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