https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62148
--- Comment #4 from aron at cohesity dot com --- Created attachment 33334 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33334&action=edit File demonstrating the pre-processor problem Attached is a file g++-bug.cc that demonstrates the problem better. Please install the libgflags-dev package on Ubuntu before testing this. g++ -Wall -c g++-bug.cc # This'll emit the warning g++ -Wall -E g++-bug.cc > preprocessed.cc g++ -Wall -c preprocessed.cc # This'll not emit the warning