https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65995
--- Comment #3 from Daniel Starke <daniel.f.starke at freenet dot de> --- I have yet to bootstrap the current trunk (r222810). It currently fails with /usr/new-gcc/bin32/./prev-gcc/xg++ -B/usr/new-gcc/bin32/./prev-gcc/ -B/mingw/mingw32/bin/ -nostdinc++ -B/usr/new-gcc/bin32/prev-mingw32/libstdc++-v3/src/.libs -B/usr/new-gcc/bin32/prev-mingw32/libstdc++-v3/libsupc++/.libs -I/usr/new-gcc/bin32/prev-mingw32/libstdc++-v3/include/mingw32 -I/usr/new-gcc/bin32/prev-mingw32/libstdc++-v3/include -I/usr/new-gcc/src/gcc-trunk/libstdc++-v3/libsupc++ -L/usr/new-gcc/bin32/prev-mingw32/libstdc++-v3/src/.libs -L/usr/new-gcc/bin32/prev-mingw32/libstdc++-v3/libsupc++/.libs -c -g -O2 -D__USE_MINGW_ACCESS -Wno-pedantic-ms-format -gtoggle -DIN_GCC -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wmissing-format-attribute -Woverloaded-virtual -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror -DHAVE_CONFIG_H -DGENERATOR_FILE -I. -Ibuild -I../../src/gcc-trunk/gcc -I../../src/gcc-trunk/gcc/build -I../../src/gcc-trunk/gcc/../include -I../../src/gcc-trunk/gcc/../libcpp/include -DPTW32_STATIC_LIB \ -o build/genmddeps.o ../../src/gcc-trunk/gcc/genmddeps.c In file included from ../../src/gcc-trunk/gcc/genmddeps.c:19:0: ../../src/gcc-trunk/gcc/system.h:1024:0: error: "CONST_CAST2" redefined [-Werror] #define CONST_CAST2(TOTYPE,FROMTYPE,X) (const_cast<TOTYPE> (X)) ^ In file included from E:/msys/new-gcc/bin32/prev-mingw32/libstdc++-v3/include/mingw32/bits/gthr.h:148:0, from E:/msys/new-gcc/bin32/prev-mingw32/libstdc++-v3/include/ext/atomicity.h:35, from E:/msys/new-gcc/bin32/prev-mingw32/libstdc++-v3/include/bits/basic_string.h:39, from E:/msys/new-gcc/bin32/prev-mingw32/libstdc++-v3/include/string:52, from ../../src/gcc-trunk/gcc/system.h:201, from ../../src/gcc-trunk/gcc/genmddeps.c:19: E:/msys/new-gcc/bin32/prev-mingw32/libstdc++-v3/include/mingw32/bits/gthr-default.h:33:0: note: this is the location of the previous definition #define CONST_CAST2(TOTYPE,FROMTYPE,X) ((__extension__(union {FROMTYPE _q; TOTYPE _nq;})(X))._nq) ^ cc1plus.exe: all warnings being treated as errors I will try to compile the trunk without bootstrap.