building with gcc 6.1 apparently fails about brial HOT 2 CLOSED

Reposting from the sage-release thread:

This seems to be the problem:
checking unordered_map usability... no
checking unordered_map presence... yes
configure: WARNING: unordered_map: present but cannot be compiled
configure: WARNING: unordered_map: check for missing prerequisite headers?
configure: WARNING: unordered_map: see the Autoconf documentation
configure: WARNING: unordered_map: section "Present But Cannot Be Compiled"
configure: WARNING: unordered_map: proceeding with the compiler's result

The configure script tests for C++11's unordered_map, which succeeds if using GCC 6. Then it tries to use it later, which of course fails because brial enforces C++98. By exporting -std=gnu++98 before running configure, the test fails so it falls back to boost's unordered_map, and the builds finishes correctly.

from brial.

There is probably two issues, it should probably use c++11 std::unordered_map. But the more pressing issue is that the std::map fallback is broken.

from brial.