# Installing GCC: Building

Now that GCC is configured, you are ready to build the compiler and runtime libraries.

We highly recommend that GCC be built using GNU make; other versions may work, then again they might not.

(For example, many broken versions of make will fail if you use the recommended setup where objdir is different from srcdir.)

## Building a native compiler

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 with "make CFLAGS='-O' LIBCFLAGS='-g -O2' LIBCXXFLAGS='-g -O2 -fno-implicit-templates' bootstrap". This will save roughly 40% of disk space both for the bootstrap and the final installation. (Libraries will still contain debugging information.)

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!

## Building a cross compiler

We recommend reading the crossgcc FAQ for information about building cross compilers.

When building a cross compiler, it is not generally possible to do a 3-stage bootstrap of the compiler. This makes for an interesting problem as parts of GCC can only be built with GCC.

To build a cross compiler, we first recommend building and installing a native compiler. You can then use the native GCC compiler to build the cross compiler.

Assuming you have already installed a native copy of GCC and configured your corss compiler, issue the command "make", which performs 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.
- Build the compiler (single stage only).
- Build runtime libraries using the compiler from the previous step.

Note that if an error occurs in any step the make process will exit.

## Building in parallel

If you have a multiprocessor you can use ``make bootstrap MAKE="make -j 2" -j 2`' 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.

Last modified on August 27, 1999.