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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - hidden visibility with shared objects lead to subtle bugs"
href="https://bugs.llvm.org/show_bug.cgi?id=50237">50237</a>
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<th>Summary</th>
<td>hidden visibility with shared objects lead to subtle bugs
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>release blocker
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Target Description Classes
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>sguelton@redhat.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>We should not set CMAKE_CXX_VISIBILITY_PRESET to hidden for llvm Targets
Using this feature is error prone and interacts in subtle ways with the LLVM
codebase.
As an example, llvm::Any::TypeId::Id relies on the uniqueness of the address of
a
static variable defined in a template function. hidden visibility implies vague
linkage for that variable, which does not guarantee the uniqueness of the
address
across a binary and a shared library. This totally breaks the implementation of
llvm::Any.
See <a href="https://gcc.gnu.org/wiki/Visibility">https://gcc.gnu.org/wiki/Visibility</a> and
<a href="https://gcc.gnu.org/onlinedocs/gcc/Vague-Linkage.html">https://gcc.gnu.org/onlinedocs/gcc/Vague-Linkage.html</a>
for more information on that topic.
Proposed patch: <a href="https://reviews.llvm.org/D101972">https://reviews.llvm.org/D101972</a></pre>
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