Preparing GCC Build

Difficulty level
Beginner

Note that this article is meant to be included into the GCC Cross-Compiler and Building GCC as they share this common section.

The GNU Compiler Collection is an advanced piece of software with dependencies. You need the following in order to build GCC:

• A Unix-like environment (Windows users can use the Windows Subsystem for Linux or Cygwin)
• Enough memory and hard disk space (it depends, 256 MiB will not be enough).
• GCC (existing release you wish to replace), or another system C compiler
• G++ (if building a version of GCC >= 4.8.0), or another system C++ compiler
• Make
• Bison
• Flex
• GMP
• MPFR
• MPC
• Texinfo
• ISL (optional)

Installing Dependencies

↓ Dependency / OS →	Source Code	Debian (Ubuntu, Mint, WSL, ...)	Gentoo	Fedora	Cygwin	OpenBSD	Arch
How to install	Normally	sudo apt install foo	sudo emerge --ask foo	sudo dnf install foo	Cygwin GUI setup	doas pkg_add foo	pacman -Syu foo
Compiler	N/A	build-essential	sys-devel/gcc	gcc gcc-c++	mingw64-x86_64-gcc-g++ / mingw64-i686-gcc-g++	Preinstalled	base-devel
Make	N/A	build-essential	dev-build/make	make	make	Preinstalled	base-devel
Bison	[1]	bison	sys-devel/bison	bison	bison	?	base-devel
Flex	[2]	flex	sys-devel/flex	flex	flex	?	base-devel
GMP	[3]	libgmp3-dev	dev-libs/gmp	gmp-devel	libgmp-devel	gmp	gmp
MPC	[4]	libmpc-dev	dev-libs/mpc	libmpc-devel	libmpc-devel	libmpc	libmpc
MPFR	[5]	libmpfr-dev	dev-libs/mpfr	mpfr-devel	libmpfr-devel	mpfr	mpfr
Texinfo	[6]	texinfo	sys-apps/texinfo	texinfo	texinfo	texinfo	base-devel
ISL (Optional)	[7]	libisl-dev	dev-libs/isl	isl-devel	libisl-devel	N/A	N/A

You need to have Texinfo installed to build Binutils. You need to have GMP, MPC, and MPFR installed to build GCC. GCC optionally can make use of the ISL library.

For instance, you can install libgmp3-dev on Debian by running the shell command: sudo apt install libgmp3-dev

Note: Version 5.x (or later) of Texinfo is known to be incompatible with the current Binutils 2.23.2 release (and older). You can check your current version using makeinfo --version. If your version is too new and you encounter problems during the build, you will need to either use Binutils 2.24 release (or newer) or install an older version of Texinfo - perhaps through building from source - and add it to your PATH prior and during the Binutils build.

Note: GCC has dropped support for CLooG in the 5.x releases [8], and many distributions have dropped the CLooG package (e.g. Gentoo in December 2022).

Note: GCC requires at least ISL version 0.15.

Note: If you are using Cygwin, it is recommended to install the libintl-devel package (I couldn't build a cross-compiler without this package)

Downloading the Source Code

Download the needed source code into a suitable directory such as $HOME/src:

• You can download the desired Binutils release by visiting the Binutils website or directly accessing the GNU main mirror.

• You can download the desired GCC release by visiting the GCC website or directly accessing the GNU main mirror.

Note: The versioning scheme used is that each fullstop separates a full number, i.e. Binutils 2.20.0 is newer than 2.9.0. This may be confusing, if you have not encountered this (quite common) versioning scheme yet, when looking at an alphanumerically sorted list of tarballs: The file at the bottom of the list is not the latest version! An easy way of getting the latest version is to sort by the last modified date and scrolling to the bottom.

Linux Users building a System Compiler

Your distribution may ship its own patched GCC and Binutils that is customized to work on your particular Linux distribution. You should be able to build a working cross-compiler using the above source code, but you might not be able to build a new system compiler for your current Linux distribution. In that case, try a newer GCC release or get the patched source code.

Gentoo Users

Gentoo offers crossdev to set up a cross-development toolchain:

   emerge -av crossdev
   crossdev --help
   PORTDIR_OVERLAY="/usr/local/crossdev" crossdev --stage1 --binutils <binutils-version> --gcc <gcc-version> --target <target>

This will install a GCC cross-compiler into a "slot", i.e. alongside already-existing compiler versions. You can install several cross-compilers that way, simply by changing target designations. An unfortunate downside is that it will also pull in gentoo patches and pass additional configure options that differ from the official GCC Cross-Compiler setup, and they might behave differently.

After the compilation finishes successfully, your cross-compiler is callable via <target>-gcc. You can also use gcc-config to toggle between compiler versions should you need to do so. Don't replace your system compiler with a cross-compiler. The package manager will also suggest updates as soon as they become available.

You can uninstall the cross-compiler by calling crossdev --clean <target>. Read the cross-development document for additional information.

Note that the version numbers to binutils and gcc are Gentoo package versions, i.e. there might be a suffix to the "official" (GNU) version that addresses additional patchsets supplied by the Gentoo maintainers. (For example, --binutils 2.24-r3 --gcc 4.8.3 is the latest stable package pair at the time of this writing.) You can omit the version numbers to use the latest package available.

Portage uses overlays to store packages that are not part of the original package management. Crossdev needs one overlay where it can store its binutils and gcc packages before building them. You can configure one properly, or you can use PORTDIR_OVERLAY to point at where it should keep its package manager files. Using PORTDIR_OVERLAY is not a good idea with existing overlays, but by then you should know how you have personally set them up earlier anyway and how to do it properly. See [9].

macOS Users

macOS users need a replacement libiconv because the system libiconv is seriously out of date. macOS users can download the latest libiconv release by visiting the libiconv website or directly accessing the GNU main FTP mirror. Otherwise you may get unresolved symbol errors related to libiconv when compiling GCC 4.3 or higher on OS X 10.4 and 10.5.

Install a new version (compile it yourself or use MacPorts) and add --with-libiconv-prefix=/opt/local (or /usr/local if you compiled it yourself) to GCC's ./configure line. Alternatively you may place the libiconv source as gcc-x.y.z/libiconv and it will be compiled as part of the GCC compilation process. (This trick also works for MPFR, GMP, and MPC).

The makefiles of Binutils and GCC use the $(CC) variable to invoke the compiler. On OS X, this resolves to gcc by default, which is actually clang. Prior to OS X 10.8, the Clang that came with Xcode's Command Line Tools package was not able to build a working GCC. Users running OS X 10.7 or below may need to find and install GCC, either from Homebrew, or from somewhere on Apple's website. You can try with the old GCC that comes preinstalled on some macOS versions.

# This is only necessary for OS X users running 10.7 or below.
export CC=/usr/bin/gcc-4.2
export CXX=/usr/bin/g++-4.2
export CPP=/usr/bin/cpp-4.2
export LD=/usr/bin/gcc-4.2

You will want to unset these exports once you compiled and installed the cross compiler.

Note for Lion users: If you're on Lion (or above) chances are that you don't have the "real" GCC since Apple removed it from the Xcode package, but you can still install it. You can do it via Homebrew or by compiling from source, both are perfectly described on a StackExchange answer.

Note for Maverick users: You can build binutils-2.24 and gcc-4.8.3 (possible other version) with Xcode 5.1.1. Note that building GCC with LLVM is not officially supported and may cause interesting bugs, if you are willing to take this risk and save time building host-gcc just to compile a cross-gcc, follow this. Install GMP, MPFR, Mpc with MacPorts.

sudo port install gmp mpfr libmpc

../binutils-2.24/configure --prefix=$PREFIX \
--target=$TARGET \
--enable-interwork --enable-multilib \
--disable-nls --disable-werror

../gcc-4.8.3/configure --prefix=$PREFIX \
--target=$TARGET \
--disable-nls \
--enable-languages=c,c++ --without-headers \
--enable-interwork --enable-multilib \
--with-gmp=/usr --with-mpc=/opt/local --with-mpfr=/opt/local

Note: There is an issue with port's GMP, so the version from OS X from /usr is used instead. Note2: If you still have some errors, try making a case-sensitive APFS disk image using disk utility app and build from there

Windows Users

Windows users need to set up a Unix-like enviroment such as MinGW or Cygwin. It may well be worth looking into systems such as Linux and see if they fit your needs, as you commonly use a lot of Unix-like tools in operating systems development and this is much easier from a Unix-like operating system. If you have just installed the basic Cygwin package, you have to run the setup.exe again and install the following packages: GCC, G++, Make, Flex, Bison, Diffutils, libintl-devel, libgmp-devel, libmpfr-devel, libmpc-devel, Texinfo

MinGW + MSYS is an option, and as it addresses the native Windows API instead of a POSIX emulation layer, results in a slightly faster toolchain. Some software packages will not build properly under MSYS as they were not designed for use with Windows. As far as this tutorial is concerned, everything that applies to Cygwin also applies to MSYS unless otherwise specified. Make sure you install the C and C++ compilers, and the MSYS Basic System.

The "Windows Subsystem for Linux (Beta)", released with the Windows 10 Anniversary update is also an option for using a cross compiler. (Tested 08/08/2016 with GCC 6.1.0 and Binutils 2.27) This cross-compiler works reasonably fast, although being in beta state, it may not be ideal permanent development platform.

Cygwin note: Cygwin includes your Windows %PATH% in its bash $PATH. If you were using DJGPP before, this could result in confusion as e.g. calling GCC on the Cygwin bash command line would still call the DJGPP compiler. After uninstalling DJGPP, you should delete the DJGPP environment variable and clear the C:\djgpp entry (or wherever you installed it) from your %PATH%. Likewise, it might be a bad idea to mix build environments in your system PATH variable.

MinGW note: Some MinGW-specific information on building a cross-toolchain can be found on the hosted cross-compiler how-to page on the MinGW homepage.

Windows Subsystem for Linux (Beta) Note: You cannot have your cross compiler in the /mnt/c/ (or /mnt/"x") areas, as trying to compile your cross-compiler there will generate errors, whereas building to $HOME/opt/cross works perfectly. This is fixed with Windows Update KB3176929

OpenBSD Users

OpenBSD users might need to install "gcc" package from ports because base system's GCC is very outdated. If you want to build GCC, try to use the ports' version instead of the latest version available and apply all patches from ports to your build. Also, if the build fails during compiling lto-plugin, a temporary solution is to disable LTO altogether during configure stage of building GCC by adding --disable-lto