std::hash<T> appears to be undefined when T is an enum type, contrary to the resolution of LWG 2148 (http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2148).
Google ref: b/8985947
Mine.
Patch available: https://gcc.gnu.org/ml/gcc-patches/2015-07/msg02162.html
Author: redi Date: Wed Jul 29 12:41:23 2015 New Revision: 226347 URL: https://gcc.gnu.org/viewcvs?rev=226347&root=gcc&view=rev Log: 2015-07-29 Ville Voutilainen <ville.voutilainen@gmail.com> PR libstdc++/60970 * include/bits/functional_hash.h (__hash_enum): New. (hash): Derive from __hash_enum. * testsuite/20_util/hash/60970.cc: New. Added: trunk/libstdc++-v3/testsuite/20_util/hash/60970.cc Modified: trunk/libstdc++-v3/ChangeLog trunk/libstdc++-v3/include/bits/functional_hash.h
Fixed for 6.1