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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW " title="NEW --- - clang compiles invalid multiple inheritance code" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D23906&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=Jh9H5txiryxDxQg1H1CO8uZFM2_K4KAuaVcSudZTEfY&s=LTQ6vE5ijDG3mIBfk46prkvt_7myyCRXshNQ8Zb_frc&e=">23906</a>
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<th>Summary</th>
<td>clang compiles invalid multiple inheritance code
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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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
</td>
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<th>Component</th>
<td>C++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>ryan.burn@gmail.com
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<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This fails to compile with gcc and EDG but compiles with clang:
#include <type_traits>
#include <utility>
#include <cassert>
template <class Tag, class Value>
class Pack
{
public:
Pack(const Value& value) : _value(value) {}
Value value() const { return _value; }
private:
Value _value;
};
template<class Tag, class Value>
decltype(auto) unpack(Tag, Pack<Tag, Value>& pack) {
return pack.value();
}
struct tag1 {};
struct tag2 {};
struct A3 : Pack<tag1, int>, Pack<tag2, double> {
A3(int x, double y) : Pack<tag1, int>(x), Pack<tag2, double>(y) {}
};
int main() {
A3 a3(1, 2);
assert(unpack(tag1(), a3) == 1);
assert(unpack(tag2(), a3) == 2);
}
Per discussion on stackoverflow
<a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__stackoverflow.com_questions_30814981_will-2Dthis-2Dtemplate-2Dfunction-2Dcorrectly-2Dmatch-2Da-2Dclass-2Dwith-2Dmultiple-2Dbases&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=Jh9H5txiryxDxQg1H1CO8uZFM2_K4KAuaVcSudZTEfY&s=M9jWNjpch_hA4S7q5XmeyDzmfSNWl3wy-b8VC1WkAKM&e=">http://stackoverflow.com/questions/30814981/will-this-template-function-correctly-match-a-class-with-multiple-bases</a>
it looks like a compiler bug with clang</pre>
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</p>
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