<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 - SEH unwinding breaks in the presence of a jump-table on Windows/AArch64"
href="https://bugs.llvm.org/show_bug.cgi?id=41581">41581</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>SEH unwinding breaks in the presence of a jump-table on Windows/AArch64
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>8.0
</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>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>gsvelto@mozilla.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>We encountered this issue when building Firefox for Windows/AArch64 using clang
8.0.0 [1]. The issue was introduced in [2].
What's happening is that we install an exception handler with
`SetUnhandledExceptionFilter()` [3] to gather crash dumps. Starting with
clang-8.0.0 this stopped working in many cases; when we encountered an
exception Windows would be unable to unwind the stack and reach the exception
handler, bailing out if it encountered a frame pointing to the JavaScript
interpreter [3] on the stack. The interpreter uses macros to generate a large
jump-table and [2] changed in which section the jump-table contents are stored.
This seems to confuse Windows' unwinding machinery which simply bails out when
encountering a frame that jumped through that table.
I've compared the code emitted w/ and w/o [2] applied and the only difference
are the section directives around the jump table. I can attach the relevant
assembly output if needed but it's very, very large.
I'm working on a reduced test-case and I'll attach it ASAP.
[1] <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1542827">https://bugzilla.mozilla.org/show_bug.cgi?id=1542827</a>
[2]
<a href="https://github.com/llvm/llvm-project/commit/502c6557aa1aa6917fe5ce0ee26cfe936d45eb98">https://github.com/llvm/llvm-project/commit/502c6557aa1aa6917fe5ce0ee26cfe936d45eb98</a>
[3]
<a href="https://searchfox.org/mozilla-central/rev/ec489aa170b6486891cf3625717d6fa12bcd11c1/js/src/vm/Interpreter.cpp#1653-4424">https://searchfox.org/mozilla-central/rev/ec489aa170b6486891cf3625717d6fa12bcd11c1/js/src/vm/Interpreter.cpp#1653-4424</a></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>