<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 - Invalid struct offsets generated"
href="https://bugs.llvm.org/show_bug.cgi?id=49456">49456</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Invalid struct offsets generated
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>6.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</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>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>lcampbel@akamai.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=24593" name="attach_24593" title="Small program demonstrating the bug">attachment 24593</a> <a href="attachment.cgi?id=24593&action=edit" title="Small program demonstrating the bug">[details]</a></span>
Small program demonstrating the bug
The attached Objective-C program, when built with gnustep-base 1.27.0 by clang
6.0.0 and run, demonstrates a bug: although 8 bytes should be allocated for
'id' types, only 4 bytes are allocated. I discovered this in a much larger
program when it segfaulted; I trimmed it down to a minimal test case.
If you remove any of the instance variables before the problematic one (_id),
the problem goes away.
If you change _enum to a char, the _id ivar gets enough space, but it's
allocated on an odd byte boundary, which is probably wrong.
If you change _enum to a short, _id is allocated only 6 bytes.
If you change _enum to an int, _id is again allocated only 4 bytes.
Compiler flags in all cases (sorry for the verbosity/redundancy, generated by a
build system I have to use):
-MMD -MP -DGNUSTEP -DGNUSTEP_BASE_LIBRARY=1 -DGNUSTEP_RUNTIME=1
-D_NONFRAGILE_ABI=1 -DGNUSTEP_BASE_LIBRARY=1 -fno-strict-aliasing -fexceptions
-fobjc-exceptions -D_NATIVE_OBJC_EXCEPTIONS -pthread -fPIC -Wall -DGSWARN
-DGSDIAGNOSE -Wno-import -Wall -Werror -m64 -march=opteron -mno-3dnow -fPIC
-ggdb -O2 -Wall -fobjc-runtime=gnustep-1.8 -fblocks
-fconstant-string-class=NSConstantString</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>