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Created attachment 1127526 [details]
Reproducing example.

Description of problem:
System headers define the identifier BIG_ENDIAN in a program that does not include any platform-specific headers, thus changing the meaning of a program that checks this particular symbol. Since BIG_ENDIAN is not a symbol reserved for the implementation, this is a standards violation.

Version-Release number of selected component (if applicable):
CentOS 7.2.1511

How reproducible:
Always.

Steps to Reproduce:
1. g++ -c big_endian_predefined.cpp

Actual results:
#error message

Expected results:
Successful compilation.

Additional info:
It looks like BIG_ENDIAN and other symbols like it become defined when __USE_BSD is defined.

The C++ compiler indeed predefines _GNU_SOURCE macro, because libstdc++ headers need various functions from that namespace.  This is a known bug, but is not going to be fixed at least until GCC 7, and requires some heavy coordination between glibc and gcc.
See e.g. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51749
Even after this is fixed upstream, this is not backportable to the RHEL 7 compiler and glibc.