How do I install GCC via Homebrew?

I am using Homebrew exclusively (i.e. I don’t, and won’t, use MacPorts or Fink). I also want to keep manual installations to a bare minimum.¹

… But how can I install GCC?

First of all, I’ve of course installed Xcode but the current version doesn’t ship with a decently up to date GCC (I need ata least 4.5, but would prefer the most recent one) – in fact, it doesn’t ship with a proper GCC at all (it only ships Clang) and that seems to be a problem for Homebrew …

I’m aware of a list of custom GCC and cross compilers but in fact all of those installations require an already installed GCC – at least, brewing them fails with linker errors on Lion which I attribute to Clang, and -use-gcc doesn’t work for obvious reasons.

brew doctor only mentions what I already know, that there is no GCC (4.2.x) installed.

¹ I’ve previously mixed MacPorts, Homebrew and some manual installations and have ended up with a maintenance and versioning hell. I don’t want to go there again.

I saw somebody link to this old post today. The best way to install GCC in homebrew right now is just brew install gcc. If you have the XCode Command Line Tools (they are separate from XCode; you can install them with xcode-select --install) installed, a precompiled version will be installed (which is very fast).

Homebrew solution

To answer my own question, homebrew-versions now has a fairly up to date formula of GCC. It can be installed using

brew install [flags] https://raw.github.com/Homebrew/homebrew-versions/gcc48.rb

Where [flags] should include all the required languages, e.g. (--enable-cxx --enable-fortran).

This will install the executables with a suffix, i.e. gcc has to be accessed as gcc-version to avoid clashes. If necessary, one can create appropriate symlinks to make this version the default.

Manual installation

Alternatively, an up-to-date GCC (as of the time of writing) can be compiled manually using the following shell script:

VERSION=4.7.0
PREFIX=/usr/gcc-$(VERSION)
LANGUAGES=c,c++,fortran
MAKE=make
# Or
# MAKE='make -j 4' # to compile using four cores

brew-path() { brew info $1 | head -n3 | tail -n1 | cut -d' ' -f1; }

# Prerequisites

brew install gmp
brew install mpfr
brew install libmpc

# Download & install the latest GCC

mkdir -p $PREFIX
mkdir temp-gcc
cd temp-gcc
wget ftp://ftp.gnu.org/gnu/gcc/gcc-$VERSION/gcc-$VERSION.tar.gz
tar xfz gcc-$VERSION.tar.gz
rm gcc-$VERSION.tar.gz
cd gcc-$VERSION

mkdir build
cd build

../configure \
   --prefix=$PREFIX \
   --with-gmp=$(brew-path gmp) \
   --with-mpfr=$(brew-path mpfr) \
   --with-mpc=$(brew-path libmpc) \
   --program-suffix=-$VERSION \
   --enable-languages=$LANGUAGES \
   --with-system-zlib \
   --enable-stage1-checking \
   --enable-plugin \
   --enable-lto \
   --disable-multilib

$MAKE bootstrap

make install

# Uncomment for cleanup …
# cd ../../..
# rm -r temp-gcc

This will stage GCC into the path /usr/gcc-4.7.0. Now all you need to do is either create symlinks to the executables or add the bin directory to the $PATH variable.