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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - unordered_map doesn't work with an enum as key in C++11 mode"
href="https://bugs.llvm.org/show_bug.cgi?id=50257">50257</a>
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<th>Summary</th>
<td>unordered_map doesn't work with an enum as key in C++11 mode
</td>
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<th>Product</th>
<td>libc++
</td>
</tr>
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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>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>ldionne@apple.com
</td>
</tr>
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<th>Reporter</th>
<td>martin@martin.st
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<p>
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<pre>A test snippet like this compiles successfully in C++14 mode but not in C++11
mode:
#include <unordered_map>
enum MyEnum { A, B, C };
std::unordered_map<MyEnum, int> myMap;
In C++11 mode, it fails like this:
In file included from libcxx-unordered-map.cpp:1:
In file included from
/home/martin/clang-nightly/x86_64-w64-mingw32/include/c++/v1/unordered_map:435:
In file included from
/home/martin/clang-nightly/x86_64-w64-mingw32/include/c++/v1/__hash_table:15:
In file included from
/home/martin/clang-nightly/x86_64-w64-mingw32/include/c++/v1/memory:668:
/home/martin/clang-nightly/x86_64-w64-mingw32/include/c++/v1/type_traits:1811:38:
error: implicit instantiation of undefined template 'std::hash<MyEnum>'
: public integral_constant<bool, __is_empty(_Tp)> {};
^
/home/martin/clang-nightly/x86_64-w64-mingw32/include/c++/v1/unordered_map:453:18:
note: in instantiation of template class 'std::is_empty<std::hash<MyEnum>>'
requested here
bool = is_empty<_Hash>::value && !__libcpp_is_final<_Hash>::value>
^
/home/martin/clang-nightly/x86_64-w64-mingw32/include/c++/v1/unordered_map:936:13:
note: in instantiation of default argument for '__unordered_map_hasher<MyEnum,
std::__hash_value_type<MyEnum, int>, std::hash<MyEnum>, std::equal_to<MyEnum>>'
required here
typedef __unordered_map_hasher<key_type, __value_type, hasher, key_equal>
__hasher;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libcxx-unordered-map.cpp:3:33: note: in instantiation of template class
'std::unordered_map<MyEnum, int>' requested here
std::unordered_map<MyEnum, int> myMap;
^
/home/martin/clang-nightly/x86_64-w64-mingw32/include/c++/v1/__memory/shared_ptr.h:1688:50:
note: template is declared here
template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
^
1 error generated.
This causes build errors when building libaom since
<a href="https://aomedia-review.googlesource.com/c/aom/+/136604">https://aomedia-review.googlesource.com/c/aom/+/136604</a>.</pre>
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