Properly passing -DWEBRTC_BSD in Gecko exposes NSPR includes <rpc/types.h> which (conditionally) defines TRUE/FALSE. FreeBSD had INADDR_LOOPBACK in <netinet/in.h> for ~21 years. Let's drop such necro-portability. http://searchfox.org/mozilla-central/rev/e8c36327cd8c/nsprpub/pr/include/prinet.h#66 https://svnweb.freebsd.org/changeset/base/21098 $ echo "ac_add_options --enable-warnings-as-errors # mimic MOZ_AUTOMATION" >>.mozconfig $ ./mach build [...] In file included from media/webrtc/signaling/src/media-conduit/AudioConduit.cpp:27: In file included from media/webrtc/trunk/webrtc/voice_engine/voice_engine_impl.h:18: In file included from media/webrtc/trunk/webrtc/voice_engine/voe_base_impl.h:18: In file included from media/webrtc/trunk/webrtc/voice_engine/shared_data.h:22: In file included from media/webrtc/trunk/webrtc/voice_engine/statistics.h:18: media/webrtc/trunk/webrtc/voice_engine/voice_engine_defines.h:295:9: error: 'FALSE' macro redefined [-Werror,-Wmacro-redefined] #define FALSE 0 ^ /usr/include/rpc/types.h:57:10: note: previous definition is here # define FALSE (0) ^ In file included from media/webrtc/signaling/src/media-conduit/AudioConduit.cpp:27: In file included from media/webrtc/trunk/webrtc/voice_engine/voice_engine_impl.h:18: In file included from media/webrtc/trunk/webrtc/voice_engine/voe_base_impl.h:18: In file included from media/webrtc/trunk/webrtc/voice_engine/shared_data.h:22: In file included from media/webrtc/trunk/webrtc/voice_engine/statistics.h:18: media/webrtc/trunk/webrtc/voice_engine/voice_engine_defines.h:296:9: error: 'TRUE' macro redefined [-Werror,-Wmacro-redefined] #define TRUE 1 ^ /usr/include/rpc/types.h:60:10: note: previous definition is here # define TRUE (1) ^ 2 errors generated.