For a native build issue the command make bootstrap. This will build the entire GCC system, which includes the following steps:

• Build host tools necessary to build the compiler such as texinfo, bison, gperf.
• Build target tools for use by the compiler such as binutils (bfd, binutils, gas, gprof, ld, and opcodes) if they have been individually linked or moved into the top level GCC source tree before configuring.
• Perform a 3-stage bootstrap of the compiler.
• Perform a comparison test of the stage2 and stage3 compilers.
• Build runtime libraries using the stage3 compiler from the previous step.

If you are short on disk space you might consider make bootstrap-lean instead. This is identical to make bootstrap except that object files from the stage1 and stage2 of the 3-stage bootstrap of the compiler are deleted as soon as they are no longer needed.

If you want to save additional space during the bootstrap and in the final installation as well, you can build the compiler binaries without debugging information as in the following example. This will save roughly 40% of disk space both for the bootstrap and the final installation. (Libraries will still contain debugging information.)

     make CFLAGS='-O' LIBCFLAGS='-g -O2' \
       LIBCXXFLAGS='-g -O2 -fno-implicit-templates' bootstrap

If you wish to use non-default GCC flags when compiling the stage2 and stage3 compilers, set BOOT_CFLAGS on the command line when doing make bootstrap. Non-default optimization flags are less well tested here than the default of -g -O2, but should still work. In a few cases, you may find that you need to specify special flags such as -msoft-float here to complete the bootstrap; or, if the native compiler miscompiles the stage1 compiler, you may need to work around this, by choosing BOOT_CFLAGS to avoid the parts of the stage1 compiler that were miscompiled, or by using make bootstrap4 to increase the number of stages of bootstrap.

If you used the flag --enable-languages=... to restrict the compilers to be built, only those you've actually enabled will be built. This will of course only build those runtime libraries, for which the particular compiler has been built. Please note, that re-defining LANGUAGES when calling make bootstrap does not work anymore!

If the comparison of stage2 and stage3 fails, this normally indicates that the stage2 compiler has compiled GCC incorrectly, and is therefore a potentially serious bug which you should investigate and report. (On a few systems, meaningful comparison of object files is impossible; they always appear "different". If you encounter this problem, you will need to disable comparison in the Makefile.)

If you have a multiprocessor system you can use make bootstrap MAKE="make -j 2" -j 2 or just make -j 2 bootstrap for GNU Make 3.79 and above instead of just make bootstrap when building GCC. You can use a bigger number instead of two if you like. In most cases, it won't help to use a number bigger than the number of processors in your machine.

In order to build GNAT, the Ada compiler, you need a working GNAT compiler (GNAT version 3.13 or later, or GCC version 3.1 or later), since the Ada front end is written in Ada (with some GNAT-specific extensions), and GNU make.

However, you do not need a full installation of GNAT, just the GNAT binary gnat1, a copy of gnatbind, and a compiler driver which can deal with Ada input (by invoking the gnat1 binary). You can specify this compiler driver by setting the ADAC environment variable at the configure step. configure can detect the driver automatically if it has got a common name such as gcc or gnatgcc. Of course, you still need a working C compiler (the compiler driver can be different or not). configure does not test whether the GNAT installation works and has a sufficiently recent version; if too old a GNAT version is installed, the build will fail unless --enable-languages is used to disable building the Ada front end.

Additional build tools (such as gnatmake) or a working GNAT run-time library installation are usually not required. However, if you want to bootstrap the compiler using a minimal version of GNAT, you have to issue the following commands before invoking make bootstrap (this assumes that you start with an unmodified and consistent source distribution):

    cd srcdir/gcc/ada
    touch treeprs.ads [es]info.h nmake.ad[bs]

At the moment, the GNAT library and several tools for GNAT are not built by make bootstrap. You have to invoke make gnatlib_and_tools in the objdir/gcc subdirectory before proceeding with the next steps.

For example, you can build a native Ada compiler by issuing the following commands (assuming make is GNU make):

    cd objdir
    srcdir/configure --enable-languages=c,ada
    cd srcdir/gcc/ada
    touch treeprs.ads [es]info.h nmake.ad[bs]
    cd objdir
    make bootstrap
    cd gcc
    make gnatlib_and_tools
    cd ..

Currently, when compiling the Ada front end, you cannot use the parallel build feature described in the previous section.