hi. i am trying to build gcc 6 (since i want to try out some c++17 features) and get an error: two systems: ubuntu 14.04 LTS A: as direct system (svn Revision: 232603) B: in virtual box (svn Revision: 232581) directories: gcc - srcdir (the svn repo) - objdir - installdir running: cd objdir ../srcdir/configure --prefix=/home/qwer/gcc/installdir/ --enable-threads --enable-link-mutex --enable-languages=c++ --disable-multilib make profiledbootstrap the failing command: on A (using the contrib/download_prerequisites script): /home/SMBAD/grimm/home/gcc/objdir/./prev-gcc/xg++ -B/home/SMBAD/grimm/home/gcc/objdir/./prev-gcc/ -B/home/qwer/gcc/installdir/x86_64-pc-linux-gnu/bin/ -nostdinc++ -B/home/SMBAD/grimm/home/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs -B/home/SMBAD/grimm/home/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs -I/home/SMBAD/grimm/home/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/x86_64-pc-linux-gnu -I/home/SMBAD/grimm/home/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include -I/home/SMBAD/grimm/home/gcc/srcdir/libstdc++-v3/libsupc++ -L/home/SMBAD/grimm/home/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs -L/home/SMBAD/grimm/home/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs -fno-PIE -c -g -O2 -fprofile-use -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 -fno-common -DHAVE_CONFIG_H -I. -I. -I../../srcdir/gcc -I../../srcdir/gcc/. -I../../srcdir/gcc/../include -I../../srcdir/gcc/../libcpp/include -I/home/SMBAD/grimm/home/gcc/objdir/./gmp -I/home/SMBAD/grimm/home/gcc/srcdir/gmp -I/home/SMBAD/grimm/home/gcc/objdir/./mpfr -I/home/SMBAD/grimm/home/gcc/srcdir/mpfr -I/home/SMBAD/grimm/home/gcc/srcdir/mpc/src -I../../srcdir/gcc/../libdecnumber -I../../srcdir/gcc/../libdecnumber/bid -I../libdecnumber -I../../srcdir/gcc/../libbacktrace -I/home/SMBAD/grimm/home/gcc/objdir/./isl/include -I/home/SMBAD/grimm/home/gcc/srcdir/isl/include -o omp-low.o -MT omp-low.o -MMD -MP -MF ./.deps/omp-low.TPo ../../srcdir/gcc/omp-low.c on B (using packages from the repo): /home/qwer/gcc/objdir/./prev-gcc/xg++ -B/home/qwer/gcc/objdir/./prev-gcc/ -B/home/qwer/gcc/installdir/x86_64-pc-linux-gnu/bin/ -nostdinc++ -B/home/qwer/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs -B/home/qwer/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs -I/home/qwer/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include/x86_64-pc-linux-gnu -I/home/qwer/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/include -I/home/qwer/gcc/srcdir/libstdc++-v3/libsupc++ -L/home/qwer/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/src/.libs -L/home/qwer/gcc/objdir/prev-x86_64-pc-linux-gnu/libstdc++-v3/libsupc++/.libs -fno-PIE -c -g -O2 -fprofile-use -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 -fno-common -DHAVE_CONFIG_H -I. -I. -I../../srcdir/gcc -I../../srcdir/gcc/. -I../../srcdir/gcc/../include -I../../srcdir/gcc/../libcpp/include -I../../srcdir/gcc/../libdecnumber -I../../srcdir/gcc/../libdecnumber/bid -I../libdecnumber -I../../srcdir/gcc/../libbacktrace -o omp-low.o -MT omp-low.o -MMD -MP -MF ./.deps/omp-low.TPo ../../srcdir/gcc/omp-low.c error (same for both modulo home directory): ../../srcdir/gcc/omp-low.c: In function ‘void expand_omp_target(omp_region*)’: ../../srcdir/gcc/omp-low.c:13345:8: error: ‘i_async’ may be used uninitialized in this function [-Werror=maybe-uninitialized] args.safe_push (oacc_launch_pack ~~~~~~~~~~~~~~~~ (GOMP_LAUNCH_ASYNC, NULL_TREE, i_async)); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ cc1plus: all warnings being treated as errors make[3]: *** [omp-low.o] Error 1 make[3]: *** Waiting for unfinished jobs.... rm gcov-tool.pod gpl.pod cpp.pod gfdl.pod fsf-funding.pod gcc.pod gcov.pod make[3]: Leaving directory `/home/qwer/gcc/objdir/gcc' make[2]: *** [all-stagefeedback-gcc] Error 2 make[2]: Leaving directory `/home/qwer/gcc/objdir' make[1]: *** [stagefeedback-bubble] Error 2 make[1]: Leaving directory `/home/qwer/gcc/objdir' make: *** [profiledbootstrap] Error 2 can someone help and tell me what i am doing wrong? thanks. raphael.