Hi! Tom Ritter: > As part of our work with Tor, we’ve been working on getting a MinGW-based > build of Windows into TaskCluster. Tor is currently using ESR releases, and > every ESR they have to go through a large amount of work to get the build > working under MinGW again; by continually building (and testing) that build > we’ll be able to cut weeks to months of effort for them each ESR release. > (Not breaking the MinGW build is also a necessity if they were ever to move > off ESRs.) > > Unlike our normal Windows builds with msvc or clang-cl, this is a > cross-compile on Linux for Windows, as well as the first time in a long > time we’ve built for Windows with gcc. Building with gcc for Windows has > exposed a number of new warnings > <https://bugzilla.mozilla.org/show_bug.cgi?id=1394433> to clean up, as well > as some C++ spec incompatibilities that MSVC (and clang-cl) accept. All of > the breaks have been resolved; and a lot of the warnings and similar are > either resolved or in-progress. > > Effective this weekend, MinGW is on Treeherder, with the single build > target win32-mingw32 (debug). Its toolchain builds are under TMW (with a > few under TL because they are generic Linux packages.) > > The one-click loaner system works for MinGW, and we’re going to allow this > to bake at Tier 2 for a while. Your help in keeping the build green is > greatly appreciated, and if you hit a MinGW bug you can’t decipher, I’ll be > happy to help, just send me an email or a needinfo. Some of the most common > things that cause errors for MinGW: > > > - #include <Windows.h> instead of #include <windows.h> and similar > > - _uuidof() instead of IID_* ref > <https://stackoverflow.com/questions/18606546/how-to-use-uuidof-in-mingw> > > - Casting nullptr to bool or int > > - Using the (in)correct assembly code > > - Breaking --disable-webrtc, --disable-sandbox, or --disable-accessibility > > - MinGW lagging behind on defining new constants Microsoft has defined > > There are a few things left outstanding > <https://bugzilla.mozilla.org/showdependencytree.cgi?id=1330608&hide_resolved=1> > for the MinGW build, including webrtc > <https://bugzilla.mozilla.org/show_bug.cgi?id=1393901>, stylo > <https://bugzilla.mozilla.org/show_bug.cgi?id=1390583> (which may be the > most difficult in this list), the sandbox > <https://bugzilla.mozilla.org/show_bug.cgi?id=1230910>, > --enable-accessibility > <https://sourceforge.net/p/mingw-w64/bugs/648/>, cleaning > up warnings <https://bugzilla.mozilla.org/show_bug.cgi?id=1394433>, and > running > tests <https://bugzilla.mozilla.org/show_bug.cgi?id=1395047>. In the > future, there is hope (by me at least) to throw all of this work away. > Compiling on Linux for Windows with clang (or clang-cl) would probably be a > significant improvement for Tor’s builds, and would enable them to take > advantage of CFI and SEH, as well as simplifying the number of platforms > Mozilla supports. Chrome has been pushing towards this > <https://bugs.chromium.org/p/chromium/issues/detail?id=495204>, so we’re > keeping an eye on their progress. > > Finally, I want to thank everyone who brought this long process to this > point: everyone who wrote patches, explained things (sometimes over and > over again), and reviewed. That’s including but not limited to: boklm, > dmajor, froydnj, glandium, georg, jacek, jrmuizel, and ted; plus the dozen > or so more people who have reviewed my patches all over the codebase.
That's great news, Tom! Thanks for working on this project and all its numerous child bugs, greatly appreciated. I know from experience how time-consuming and tedious this is. To stress a point you made in your email above: your efforts and those of other Mozilla engineers that helped with this project does indeed save us weeks of work when preparing major Tor Browser releases based on a new ESR. We can now use this valuable time to fix more privacy issues faster which benefits both Tor Browser and Firefox users alike because we upstream those patches as we think not only Tor users should benefit from them. As to your future plans, yes, we are happy if we can help with the effort to move away from using GCC for Windows cross-builds and move to clang instead. That's not only due to the SEH and CFI support you mentioned. Rather, it would allow us to get rid of annoying GCC bugs, like https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64384, as well and would significantly simpify our cross-compile setups we need to maintain. Thanks, Georg
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