PATH_HOLD=$PATH : This command stores your current path before it's modified so that it can be restored after installation. export PATH=/opt/gnat/bin:$PATH : This command allows the build to find GNAT's Ada compiler to build Ada. touch treeprs.ads [es]info.h nmake.ad[bs] : This command creates necessary files for the Ada build. This step may be skipped if you don't want to compile the Ada frontend. CC=/usr/bin/gcc : This command works around the new PATH which puts GNAT 's gcc as the primary compiler. --enable-languages=c,c++,objc,f77,ada,java : This command builds all available languages in the GCC package. You may modify this command to remove unwanted languages. --enable-shared --enable-threads=posix --enable-__cxa_atexit : These commands are required to build the C++ libraries to published standards. --enable-clocale=gnu : This command is a failsafe for incomplete locale data. make gnatlib_and tools : This command completes the Ada build process. Skip this step if you have not enabled Ada as one of the languages.