当我尝试安装gcc49时，我收到一个错误
$ brew install https://raw.githubusercontent.com/Homebrew/homebrew-versions/master/gcc49.rb
######################################################################## 100.0%
==> Downloading http://ftpmirror.gnu.org/gcc/gcc-4.9.3/gcc-4.9.3.tar.bz2
Already downloaded: /Library/Caches/Homebrew/gcc49-4.9.3.tar.bz2
==> ../configure --build=x86_64-apple-darwin14.5.0 --prefix=/usr/local/Cellar/gcc49/4.9.3 --libdir=/usr/local/Cellar/gcc49/4.9.3/lib/gcc/4.9 --enable-languages=c,c++,objc,obj-c++ --program-suffix=-4.9 --w
checking for version 0.10 of ISL... no
checking for version 0.11 of ISL... no
checking for version 0.12 of ISL... no
checking for version 0.14 of ISL... no
configure: error: Unable to find a usable ISL. See config.log for details.
Warning: It appears you have MacPorts or Fink installed.
Software installed with other package managers causes known problems for
Homebrew. If a formula fails to build, uninstall MacPorts/Fink and try again.
READ THIS: https://git.io/brew-troubleshooting
但是，我有ISL:
$ brew info isl
isl: stable 0.14.1 (bottled), HEAD
Integer Set Library for the polyhedral model
http://freecode.com/projects/isl
/usr/local/Cellar/isl/0.14.1 (68 files, 3.2M) *
Poured from bottle
From: https://github.com/Homebrew/homebrew/blob/master/Library/Formula/isl.rb
==> Dependencies
Build: xz ✔
Required: gmp ✔
我不知道config.log在哪里
安装GCC 4.9的正确方法是使用
$ brew install homebrew/versions/gcc49
这样，Homebrew将正确解决缺失的依赖并为您安装它们。你可以使用
找到这个版本的gcc(或任何其他)$ brew search gcc49
homebrew/versions/gcc49
或
$ brew search gcc
gcc homebrew/versions/gcc47
homebrew/dupes/apple-gcc42 homebrew/versions/gcc48
homebrew/versions/gcc43 homebrew/versions/gcc49
homebrew/versions/gcc44 homebrew/versions/gcc5
homebrew/versions/gcc45 homebrew/versions/llvm-gcc28
homebrew/versions/gcc46
但是，您缺少的依赖关系不是isl，而是isl011。你可以用
$ brew install isl011
我们可以看到这是gcc49与
$ brew info gcc49
==> Dependencies
Required: gmp4 ✔, libmpc08 ✔, mpfr2 ✔, cloog018 ✔, isl011 ✔
问题是由更新的Xcode引起的。需要运行:"$ xcode-select——install"