1446428 - WebRTC compiles have lots of C4005 redefinition warnings

Status: NEW

(Firefox Build System :: General, defect)

Description

[(not currently active) Ted Mielczarek]

I noticed this in my Windows build today:
 6:02.85 gain_control_impl.cc
 6:02.85 c:/build/mozilla-central/obj-x86_64-pc-linux-gnu/mozilla-config.h(130): warning C4005: 'WINVER': macro redefinition
 6:02.86 c:/build/mozilla-central/obj-x86_64-pc-linux-gnu/mozilla-config.h(130): note: command-line arguments:  see previous definition of 'WINVER'
 6:02.86 c:/build/mozilla-central/obj-x86_64-pc-linux-gnu/mozilla-config.h(139): warning C4005: '_WIN32_WINNT': macro redefinition
 6:02.86 c:/build/mozilla-central/obj-x86_64-pc-linux-gnu/mozilla-config.h(139): note: command-line arguments:  see previous definition of '_WIN32_WINNT'

I can see in the json files in the tree that are generated from the gn build files that these defines exist:
https://dxr.mozilla.org/mozilla-central/rev/6ff60a083701d08c52702daf50f28e8f46ae3a1c/media/webrtc/gn-configs/x64_False_x64_win.json#91

They seem to come from this gn file:
https://dxr.mozilla.org/mozilla-central/rev/6ff60a083701d08c52702daf50f28e8f46ae3a1c/media/webrtc/trunk/build/config/win/BUILD.gn#198

It would be nice to silence these warnings. We could do something simple, like have a list of defines that we don't want to use from the gn config, or we could do something more complicated and check the global list of DEFINES and ignore entries from the gn file that attempt to override those. I don't think we have anything in moz.build that prevents this same situation from happening there, but it's less likely because these sorts of global defines tend to get set in configure.