Compiling GCC-SVN on MacOS 10.14.5

Again SIP has brought along some user-visible changes (see previous issue with Apple Mail). With the update of XCode 10 the directory /usr/include is not available anymore — not even after installing XCode and xcode-select --install. Without /usr/include, one cannot compile the GNU Compiler from source anymore. The forum’s preferred solution is to install the package /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg

Prior to compiling GCC, one needs updated libraries, e.g. using brew: brew update. Then run brew install gmp mpfr libmpc isl

My configure line for GCC currently is:

../configure --prefix=$PWD/usr --enable-bootstrap --enable-languages=c,c++,fortran,jit,lto --enable-host-shared --disable-multiarch

The options mean:

• --prefix= Installation path is in the present working directory under usr/. This allows prepending this installation’s bin directory to my PATH (and equivalent for the library’s directory to LD_LIBRARY_PATH) in order to test the new compiler.
• --enable-bootstrap After compiling GCC with the system compiler (Apple uses an adapted Clang compiler), recompile GCC with itself in multiple sttages.
• --enable-languages Apart from C and C++, compile with the Fortran compiler, the Just-in-Time compilation support (which requires --enable-host-shared) and link-time-optimization frontend (to allow optimization at the final link-step, which offers more optimization opportunities).
• --enable-host-shared The GCC-internal host libraries are build as shared libraries. These are required to be dynamically loadable at runtime by applications compiling just-in-time code.
• --disable-multilib Just compile natively for x86_64-architecture, do not compile multi-library version, e.g. 32-bit i386.

Alternatively using --with-native-system-header-dir one may search for header files in the directory found above, not in the non-existent /usr/include; so here, this would be --with-native-system-header-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include.