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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Over-eager template instantiation breaks libstdc++ variant from gcc 10 trunk"
href="https://bugs.llvm.org/show_bug.cgi?id=43087">43087</a>
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<th>Summary</th>
<td>Over-eager template instantiation breaks libstdc++ variant from gcc 10 trunk
</td>
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<th>Product</th>
<td>clang
</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
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++17
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>David.Truby@arm.com
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=22414" name="attach_22414" title="Simple reproducing case">attachment 22414</a> <a href="attachment.cgi?id=22414&action=edit" title="Simple reproducing case">[details]</a></span>
Simple reproducing case
libstdc++ 10 has changes to its variant implementation that cause compilation
to fail with clang. I've attached a file that works with clang and libc++ and
also with gcc and libstdc++. It seems that clang is over-eager when
instantiating the templates and goes looking for a constructor further down the
nested stack when there's a valid one higher up.
The same problem did manifest with libc++, but was fixed by this commit:
<a href="https://github.com/llvm-mirror/libcxx/commit/301501fb78f90d65cec68f22144f3446a571e553#diff-9308c8fc46861ae969c076f9b7637013">https://github.com/llvm-mirror/libcxx/commit/301501fb78f90d65cec68f22144f3446a571e553#diff-9308c8fc46861ae969c076f9b7637013</a>
However, since clang has had the same problem with both libc++ and libstdc++,
and gcc doesn't have the same problem with libstdc++, I suspect this represents
a bug at the clang end.</pre>
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