<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 - GCC and Clang disagree about packed record layout with non-POD fields"
href="https://bugs.llvm.org/show_bug.cgi?id=51839">51839</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>GCC and Clang disagree about packed record layout with non-POD fields
</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>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Frontend
</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>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>Consider:
<a href="https://gcc.godbolt.org/z/P4EKvYfr5">https://gcc.godbolt.org/z/P4EKvYfr5</a>
struct NonPod {
NonPod(); // matters
long long i64;
};
struct __attribute__ ((packed)) Packed {
char c;
NonPod a;
};
int theSize = sizeof(Packed);
GCC gives a size of 16, while clang gives a size of 9.
GCC also produces this warning:
warning: ignoring packed attribute because of unpacked non-POD field 'NonPod
Packed::a'
7 | NonPod a;
| ^
At this point, changing Clang's behavior would probably be a major ABI break.
Presumably this is a no-go for distributors unconcerned with GCC compatibility.
Therefore, it seems we need a LangOpt or something to control this behavior.</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>