Apple - How do I install GCC via Homebrew?

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.

The solution provided by @Konrad Rudolph is not entirely correct anymore as the GCC formula that he mentioned was moved from homebrew/dupes to homebrew/versions. You can choose which version of GCC to install. For example, at the time of writing this answer, version 4.5, 4.7 and 4.8 are available. You may check out what versions are available here.

In short, you can install GCC 4.8 by using

brew tap homebrew/versions
brew install [flags] gcc48

You can view available install flags by using

brew options gcc48

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).