Add gdb::hash_enum
The DWARF-5 .debug_names consumer patch will want to use an
std::unordered_map with an enum as key type, like:
std::unordered_map<sect_offset, dwarf2_per_cu_data*>
That doesn't work in C++11 in non-recent compilers due to a language
defect:
http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2148
~~~
In file included from /usr/include/c++/5.3.1/bits/hashtable.h:35:0,
from /usr/include/c++/5.3.1/unordered_set:47,
from src/gdb/dwarf2read.c:79:
/usr/include/c++/5.3.1/bits/hashtable_policy.h: In instantiation of ‘struct std::__detail::__is_noexcept_hash<sect_offset, std::hash<sect_offset> >’:
/usr/include/c++/5.3.1/type_traits:137:12: required from ‘struct std::__and_<std::__is_fast_hash<std::hash<sect_offset> >, std::__detail::__is_noexcept_hash<sect_offset, std::hash<sect_offset> > >’
/usr/include/c++/5.3.1/type_traits:148:38: required from ‘struct std::__not_<std::__and_<std::__is_fast_hash<std::hash<sect_offset> >, std::__detail::__is_noexcept_hash<sect_offset, std::hash<sect_offset> > > >’
/usr/include/c++/5.3.1/bits/unordered_map.h:100:66: required from ‘class std::unordered_map<sect_offset, dwarf2_per_cu_data*>’
src/gdb/dwarf2read.c:3260:30: required from here
/usr/include/c++/5.3.1/bits/hashtable_policy.h:85:34: error: no match for call to ‘(const std::hash<sect_offset>) (const sect_offset&)’
noexcept(declval<const _Hash&>()(declval<const _Key&>()))>
^
In file included from /usr/include/c++/5.3.1/bits/move.h:57:0,
from /usr/include/c++/5.3.1/bits/stl_pair.h:59,
from /usr/include/c++/5.3.1/bits/stl_algobase.h:64,
from /usr/include/c++/5.3.1/bits/char_traits.h:39,
from /usr/include/c++/5.3.1/string:40,
from /home/pedro/gdb/mygit/src/gdb/common/common-utils.h:23,
from /home/pedro/gdb/mygit/src/gdb/common/common-defs.h:78,
from /home/pedro/gdb/mygit/src/gdb/defs.h:28,
from /home/pedro/gdb/mygit/src/gdb/dwarf2read.c:31:
~~~
This commits adds a helper replacement.
gdb/ChangeLog:
2017-12-08 Pedro Alves <palves@redhat.com>
* common/hash_enum.h: New file.2 files changed
