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<head>
<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - rL256003 breaks LTO with debug info"
href="https://llvm.org/bugs/show_bug.cgi?id=25915">25915</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>rL256003 breaks LTO with debug info
</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>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>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>krasin@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Consider the following program:
$ cat lala.cc
const char lala[] = { 0 };
Let's compile it with -flto and -g, and link using Gold plugin:
$ /usr/local/google/home/krasin/src/llvm.org/release-build/bin/clang++ -flto -g
-fuse-ld=gold -o lala lala.cc
clang-3.8: error: unable to execute command: Segmentation fault (core dumped)
clang-3.8: error: linker command failed due to signal (use -v to see
invocation)
Gold under gdb:
Program received signal SIGSEGV, Segmentation fault.
(anonymous namespace)::IRLinker::findNeededSubprograms
(this=this@entry=0x7fffffff6350, ValueMap=...) at
/usr/local/google/home/krasin/src/llvm.org/llvm/lib/Linker/IRMover.cpp:1196
1196 for (const Metadata *Op : CU->getSubprograms()->operands()) {
(gdb) bt
#0 (anonymous namespace)::IRLinker::findNeededSubprograms
(this=this@entry=0x7fffffff6350, ValueMap=...) at
/usr/local/google/home/krasin/src/llvm.org/llvm/lib/Linker/IRMover.cpp:1196
#1 0x00007ffff454e361 in linkNamedMDNodes (this=0x7fffffff6350) at
/usr/local/google/home/krasin/src/llvm.org/llvm/lib/Linker/IRMover.cpp:1250
#2 run (this=0x7fffffff6350) at
/usr/local/google/home/krasin/src/llvm.org/llvm/lib/Linker/IRMover.cpp:1520
#3 llvm::IRMover::move(llvm::Module&, llvm::ArrayRef<llvm::GlobalValue*>,
std::function<void (llvm::GlobalValue&, std::function<void
(llvm::GlobalValue&)>)>, llvm::DenseMap<unsigned int, llvm::MDNode*,
llvm::DenseMapInfo<unsigned int>, llvm::detail::DenseMapPair<unsigned int,
llvm::MDNode*> >*, bool) (this=this@entry=0x7fffffff6a30, Src=...,
ValuesToLink=..., AddLazyFor=..., ValIDToTempMDMap=ValIDToTempMDMap@entry=0x0,
IsMetadataLinkingPostpass=IsMetadataLinkingPostpass@entry=false) at
/usr/local/google/home/krasin/src/llvm.org/llvm/lib/Linker/IRMover.cpp:1654
#4 0x00007ffff3be433d in allSymbolsReadHook (ApiFile=ApiFile@entry=0x0) at
/usr/local/google/home/krasin/src/llvm.org/llvm/tools/gold/gold-plugin.cpp:910
#5 0x00007ffff3be66ab in all_symbols_read_hook () at
/usr/local/google/home/krasin/src/llvm.org/llvm/tools/gold/gold-plugin.cpp:955
#6 0x00000000004d5aef in ?? ()
#7 0x00000000004d5c24 in ?? ()
#8 0x0000000000516c65 in ?? ()
#9 0x0000000000516fca in ?? ()
#10 0x0000000000404f32 in ?? ()
#11 0x00007ffff7313ec5 in __libc_start_main (main=0x404a80, argc=37,
argv=0x7fffffffd708, init=<optimized out>, fini=<optimized out>,
rtld_fini=<optimized out>, stack_end=0x7fffffffd6f8) at libc-start.c:287
#12 0x0000000000405e41 in ?? ()
This is introduced in <a href="http://reviews.llvm.org/rL256003">http://reviews.llvm.org/rL256003</a> and the immediate
problem is in the line IRMover.cpp:1197 that makes an assumption that
CU->getSubprograms() will always return a non-NULL value.
This was initially discovered on one of Chromium buildbots, see
<a href="https://crbug.com/570694#c14">https://crbug.com/570694#c14</a></pre>
</div>
</p>
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