https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90558
--- Comment #5 from Iain Sandoe <iains at gcc dot gnu.org> --- (In reply to Rich Townsend from comment #0) > I'm running into a bug building on OSX Mojave, which seems to be tied into > the problems with _Atomic in Apple's system headers. The error itself is: > /Users/townsend/devel/sdk2/build/gcc/configure CC= > --build=x86_64-apple-darwin18.5.0 --prefix=/Applications/mesasdk-dev > --with-gmp=/Applications/mesasdk-dev --with-mpfr=/Applications/mesasdk-dev > --with-mpc=/Applications/mesasdk-dev --enable-languages=c,c++,fortran > --disable-multilib --disable-nls --disable-libsanitizer --with-sysroot=/ > --with-build-sysroot=/Users/townsend/devel/sdk2/build/xcode > > The messing around with --with-sysroot and --with-build-sysroot is so that > the resulting compiler can be used on older OSX versions, without any > undefined symbols cropping up. My understanding of these flags is that: This part is a duplicate of https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79885 there's an experimental patch at comment #10