__cplusplus on RHEL 7.

gcc version

gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/4.8.5/lto-wrapper
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-bootstrap --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-linker-hash-style=gnu --enable-languages=c,c++,objc,obj-c++,java,fortran,ada,go,lto --enable-plugin --enable-initfini-array --disable-libgcj --with-isl=/builddir/build/BUILD/gcc-4.8.5-20150702/obj-x86_64-redhat-linux/isl-install --with-cloog=/builddir/build/BUILD/gcc-4.8.5-20150702/obj-x86_64-redhat-linux/cloog-install --enable-gnu-indirect-function --with-tune=generic --with-arch_32=x86-64 --build=x86_64-redhat-linux
Thread model: posix
gcc version 4.8.5 20150623 (Red Hat 4.8.5-11) (GCC)

result.console.log

[mockbuild@localhost ~]$ g++ test.cpp
[mockbuild@localhost ~]$ ./a.out
199711
Older
[mockbuild@localhost ~]$ g++ -g -O2 -std=c++11 -g -O2 -DRELEASE test.cpp
[mockbuild@localhost ~]$ ./a.out
201103
Newer

test.cpp

#include <iostream>
int main() {
        std::cout << __cplusplus << std::endl;
#if __cplusplus >= 201103L
        std::cout << "Newer" << std::endl;
#else
        std::cout << "Older" << std::endl;
#endif
}