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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Code for virtual function not generated"
href="https://bugs.llvm.org/show_bug.cgi?id=45953">45953</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Code for virtual function not generated
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</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>C++17
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>profclonk@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=23496" name="attach_23496" title="Test code">attachment 23496</a> <a href="attachment.cgi?id=23496&action=edit" title="Test code">[details]</a></span>
Test code
For the attached C++17 code involving Boost.Beast, clang++ gives an "undefined
symbol" error (full message below). It appears that the code for the function
"boost::beast::stable_async_base<...>::before_invoke_hook()" is not generated,
leading to the error. It works with g++.
The error occurs with the LLVM 10.0.0 prebuilt binary for Ubuntu x86_64 and
using the Boost library version 1.73.0, on Linux Mint 19.3. It happens with
both LD and LLD. The Boost libraries were compiled with clang as well, but I
think this is not really relevant as the missing function is a template and
should be generated when compiling the application.
The code is compiled with "clang++ test.cpp -fuse-ld=lld -lboost_system
-pthread -lssl -lcrypto".
This is the missing function:
<a href="https://github.com/boostorg/beast/blob/boost-1.73.0/include/boost/beast/core/async_base.hpp#L193">https://github.com/boostorg/beast/blob/boost-1.73.0/include/boost/beast/core/async_base.hpp#L193</a>
The attached code of course makes zero sense, but appears to be the minimal
amount that reproduces the problem. It is unnecessarily contrived and I have
since been pointed to a better (and working) solution, but there may still be a
bug in Clang/LLVM that could be worth fixing.
The full linker error is:
ld.lld: error: undefined symbol: boost::beast::stable_async_base<void
LoaderConnection::onResolve<int>(int&&, boost::system::error_code const&,
boost::asio::ip::basic_resolver_results<boost::asio::ip::tcp>
const&)::'lambda'(boost::system::error_code const&, unsigned long),
boost::asio::executor, std::allocator<void> >::before_invoke_hook()
<span class="quote">>>> referenced by test.cpp
>>> /tmp/test-223f2a.o:(vtable for boost::beast::http::detail::write_msg_op<void LoaderConnection::onResolve<int>(int&&, boost::system::error_code const&, boost::asio::ip::basic_resolver_results<boost::asio::ip::tcp> const&)::'lambda'(boost::system::error_code const&, unsigned long), boost::beast::ssl_stream<boost::beast::basic_stream<boost::asio::ip::tcp, boost::asio::executor, boost::beast::unlimited_rate_policy> >, true, boost::beast::http::empty_body, boost::beast::http::basic_fields<std::allocator<char> > >)
>>> referenced by test.cpp
>>> /tmp/test-223f2a.o:(vtable for boost::beast::stable_async_base<void LoaderConnection::onResolve<int>(int&&, boost::system::error_code const&, boost::asio::ip::basic_resolver_results<boost::asio::ip::tcp> const&)::'lambda'(boost::system::error_code const&, unsigned long), boost::asio::executor, std::allocator<void> >)</span >
ld.lld: error: undefined symbol:
boost::beast::detail::allocate_stable_state<boost::beast::http::serializer<true,
boost::beast::http::empty_body,
boost::beast::http::basic_fields<std::allocator<char> > >, std::allocator<void>
<span class="quote">>::~allocate_stable_state()
>>> referenced by test.cpp
>>> /tmp/test-223f2a.o:(vtable for boost::beast::detail::allocate_stable_state<boost::beast::http::serializer<true, boost::beast::http::empty_body, boost::beast::http::basic_fields<std::allocator<char> > >, std::allocator<void> >)</span >
ld.lld: error: undefined symbol:
boost::beast::detail::allocate_stable_state<boost::beast::http::serializer<true,
boost::beast::http::empty_body,
boost::beast::http::basic_fields<std::allocator<char> > >, std::allocator<void>
<span class="quote">>::~allocate_stable_state()
>>> referenced by test.cpp
>>> /tmp/test-223f2a.o:(vtable for boost::beast::detail::allocate_stable_state<boost::beast::http::serializer<true, boost::beast::http::empty_body, boost::beast::http::basic_fields<std::allocator<char> > >, std::allocator<void> >)</span >
ld.lld: error: undefined symbol:
boost::beast::detail::allocate_stable_state<boost::beast::http::serializer<true,
boost::beast::http::empty_body,
boost::beast::http::basic_fields<std::allocator<char> > >, std::allocator<void>
<span class="quote">>::destroy()
>>> referenced by test.cpp
>>> /tmp/test-223f2a.o:(vtable for boost::beast::detail::allocate_stable_state<boost::beast::http::serializer<true, boost::beast::http::empty_body, boost::beast::http::basic_fields<std::allocator<char> > >, std::allocator<void> >)</span >
clang-10: error: linker command failed with exit code 1 (use -v to see
invocation)</pre>
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