<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 - Don't assume we only have one CU when parsing .debug_line"
href="https://bugs.llvm.org/show_bug.cgi?id=36793">36793</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Don't assume we only have one CU when parsing .debug_line
</td>
</tr>
<tr>
<th>Product</th>
<td>lld
</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>ELF
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jh7370.2008@my.bristol.ac.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>In LLD, we currently parse the .debug_line section in an object file to emit
source information when we can for undefined symbol errors. The code currently
assumes that there is only a single CU in the object file, and therefore that
the offset of the line table corresponding to that CU is always zero. This
isn't always true. I can think of at least three different cases for this
situation:
1) Objects built by combining multiple objects in a -r link.
2) Objects made via LTO.
3) Objects built from hand-written assembly.
We can probably ignore 3), but 1) and 2) are more important, and can result in
undefined symbol errors being reported with missing line information:
// test.c
int foobar();
int _start()
{
return foobar();
}
// test2.c
int baz();
int foobar()
{
return baz();
}
C:\Work> clang.exe -target x86_64-pc-linux -c test.c test2.c -g
C:\Work> ld.lld.exe test.o test2.o -o test.ro -r
C:\Work> ld.lld.exe test2.o test.o -o test2.ro -r
C:\Work> ld.lld.exe test.ro -o test.elf
C:\Work\ld.lld.exe: error: undefined symbol: baz
<span class="quote">>>> referenced by test.ro:(foobar)</span >
C:\Work> ld.lld.exe test2.ro -o test.elf
C:\Work\ld.lld.exe: error: undefined symbol: baz
<span class="quote">>>> referenced by test2.c:5
>>> test2.ro:(foobar)</span ></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>