<html>
<head>
<base href="http://llvm.org/bugs/" />
</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 --- - [-cxx-abi microsoft] Trivially adjustable covariant return types should not require a thunk"
href="http://llvm.org/bugs/show_bug.cgi?id=18298">18298</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[-cxx-abi microsoft] Trivially adjustable covariant return types should not require a thunk
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>rnk@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, timurrrr@google.com
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Clang emits a no-op return adjusting thunk for this code, but more importantly,
it adds a slot to D's vtable, which is an ABI problem:
$ cat t.cpp
struct A { };
struct B : A {};
struct C { virtual A *f(); };
struct D : C { virtual B *f(); };
D d;
MSVC creates a single-entry vftable for D, while clang gives it two entries.
I realized this after committing r197836, which only scratched the surface of
the problem. We need to actually calculate the adjustment and see if it is
empty.</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>