今天在10.7.4试用Xcode4.3和10.8 dp4试用4.5,发现安装完以后，没有gcc。苹果真厉害，Xcode也类似于绿色软件，原因如下
Apple announced Xcode 4.3 for OSX Lion and 4.4 for OSX Mountain Lion last week. The major difference is that Xcode no longer provide an installer which is good thing because you now could update Xcode with AppStore in the future, plus it is much easier to carry the development environment with you. However, there is a little problem with this new version of Xcode, is that all command line toolsets and compilers are not visible in terminal.也就是你下载xcode.app，一切就有了。
使用gcc方法。加入下面到.bash_profile
export PATH=/Volumes/Xcode/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin:/Volumes/Xcode/Xcode.app/Contents/Developer/usr/bin:$PATH