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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [ARM] - LLD does not deduplicate entries in .ARM.exidx"
href="https://bugs.llvm.org/show_bug.cgi?id=34501">34501</a>
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<th>Summary</th>
<td>[ARM] - LLD does not deduplicate entries in .ARM.exidx
</td>
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<th>Product</th>
<td>lld
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>ELF
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>grimar@accesssoftek.com
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>It was spotted in comments for PR34407 that
when linking sample with LLD and gnu ld (sample can be taken from following
reply: <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - lld does not seem to honour the linker script load address"
href="show_bug.cgi?id=34407#c2">https://bugs.llvm.org/show_bug.cgi?id=34407#c2</a>) the size of
.ARM.exidx produced is different.
gnu ld output is:
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf
Al
[ 3] .ARM.exidx ARM_EXIDX 0001f098 00f098 000008 00 AL 2 0
4
Unwind table index '.ARM.exidx' at offset 0xf098 contains 1 entries:
0x1f008 <main>: 0x1 [cantunwind]
and LLD's is:
Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf
Al
[ 3] .ARM.exidx ARM_EXIDX 0001f098 001098 000018 00 AL 2 0
4
Unwind table index '.ARM.exidx' at offset 0x1098 contains 3 entries:
0x1f008 <main>: 0x1 [cantunwind]
0x1f03e <putc>: 0x1 [cantunwind]
0x1f05a <putc+0x1c>: 0x1 [cantunwind]
So LLD produces 3x size of .ARM.exidx at this moment.
I know almost nothing about ARM, but after quick investigation found that gnu
ld do some proccessing for SHT_ARM_EXIDX sections.
One of stepd is deduplicating of entries. Patch implementing this was:
<a href="https://sourceware.org/ml/binutils/2009-05/msg00048.html">https://sourceware.org/ml/binutils/2009-05/msg00048.html</a>
And also looks they had to add --no-merge-exidx-entries flag to be able
to disable deduplication
(<a href="https://sourceware.org/ml/binutils/2010-04/msg00193.html">https://sourceware.org/ml/binutils/2010-04/msg00193.html</a>).
Not sure do we want to support this or not, reporting the difference just in
case.</pre>
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