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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - lld + LTO: symbol __start_($SECTION_NAME) is missing type"
href="https://llvm.org/bugs/show_bug.cgi?id=30680">30680</a>
</td>
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<tr>
<th>Summary</th>
<td>lld + LTO: symbol __start_($SECTION_NAME) is missing type
</td>
</tr>
<tr>
<th>Product</th>
<td>lld
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<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>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>Created <span class=""><a href="attachment.cgi?id=17429" name="attach_17429" title="the reproducer">attachment 17429</a> <a href="attachment.cgi?id=17429&action=edit" title="the reproducer">[details]</a></span>
the reproducer
Consider the following shared object (the full reproducer is attached):
bar.cc:
__attribute((visibility("default"))) __attribute__ ((section("play_go")))
void* get_start();
extern "C" char __start_play_go[] __attribute__((weak));
void* get_start() {
return reinterpret_cast<void*>(__start_play_go);
}
Basically, we put get_start function into play_go section and also use
__start_play_go symbol to keep it there.
Then we try to use this symbol from main.cc
#include <stdio.h>
extern "C" char __start_play_go[] __attribute__((weak));
int main(void) {
printf("__start_play_go: %p\n", __start_play_go);
}
Building:
$ clang++ -shared -o libbar.so bar.cc
$ clang++ -c main.cc -flto
$ clang++ -o sections main.o libbar.so -flto -fuse-ld=lld
symbol __start_play_go is missing type
clang-3.9: error: linker command failed with exit code 1 (use -v to see
invocation)
I observe that while building Chromium, as tcmalloc uses this dark magic of
sections for hooks.</pre>
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