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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.