I'm getting local build errors on OSX related to the element size asserts added in bug 1363375: /Users/jon/work/modules/dom/base/Element.cpp:183:1: error: static_assert failed "DOM size changed" ASSERT_ELEMENT_SIZE(Element, 120); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /Users/jon/work/modules/dom/base/Element.cpp:178:3: note: expanded from macro 'ASSERT_ELEMENT_SIZE' static_assert(sizeof(void*) != 8 || a == b, "DOM size changed"); \ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /Users/jon/work/modules/dom/base/Element.cpp:183:1: note: in instantiation of template class 'CheckElementSize<128, 120>' requested here /Users/jon/work/modules/dom/base/Element.cpp:180:69: note: expanded from macro 'ASSERT_ELEMENT_SIZE' Check##type##Size<sizeof(type), opt_size + EXTRA_DOM_ELEMENT_BYTES> g##type##CES; ^ <scratch space>:38:1: note: expanded from here gElementCES ^ OSX version: 10.12.4 $ /usr/bin/clang --version Apple LLVM version 8.1.0 (clang-802.0.42) Target: x86_64-apple-darwin16.5.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin $ cat opt-build/mozconfig . $topsrcdir/browser/config/mozconfig CC='clang' CXX='clang++' mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/opt-build mk_add_options MOZ_MAKE_FLAGS="-s -j8" ac_add_options --with-ccache=/usr/local/bin/ccache mk_add_options AUTOCONF=/usr/local/bin/autoconf213 mk_add_options AUTOCLOBBER=1 ac_add_options --disable-debug ac_add_options --enable-optimize ac_add_options --disable-profiling

This is presumably because of --disable-profiling. This should be fixed with bug 1365954.