问题
I've recently updated to Mountain Lion and re-installed Ruby, but when I try to run a test Rails app, I get an error message that says that "Rails is not currently installed" on my system. I do what it says, type sudo gem install rails and get:
cleared faster_require caches due to new gem install...
Successfully installed rails-3.2.7
1 gem installed
Installing ri documentation for rails-3.2.7...
Installing RDoc documentation for rails-3.2.7...
But when I check to see which rails version is install, here is what I get:
Rails is not currently installed on this system. To get the latest version, simply type:
$ sudo gem install rails
You can then rerun your "rails" command.
I've also tried gem install rails and get:
Building native extensions. This could take a while...
ERROR: Error installing rails:
ERROR: Failed to build gem native extension.
/Users/aileen/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
creating Makefile
make
compiling generator.c
make: /usr/bin/gcc-4.2: No such file or directory
make: *** [generator.o] Error 1
Gem files will remain installed in /Users/aileen/.rvm/gems/ruby-1.9.3-p194@rails327/gems/json-1.7.4 for inspection.
Results logged to /Users/aileen/.rvm/gems/ruby-1.9.3-p194@rails327/gems/json-1.7.4/ext/json/ext/generator/gem_make.out
回答1:
I see that you are using ruby 1.9.3 using rvm on OS X 10.8.2 (Mountain lion) It's possible that some gems referenced by rails need gcc-4.2 in /usr/bin to build native estension.
In Mountain Lion , even after installing Xcode 4.5 CLI tools ( opening the menu XCode - Preferences..Download -> Command Line Tools ) you get /usr/bin/gcc but not /usr/bin/gcc-4.2; unfortunately the build process of some native extension relies on /usr/bin/gcc-4.2
However I just installed rails smoothly on an environment such as your. I previously fixed the environment as discussed in the Carina C. Zona's blog post: Fix for “make: /usr/bin/gcc-4.2: No such file or directory”, that is:
make sure you have installed Homebrew
brew --version
should report 0.9.3 or greater
- if you have not brew than follow these instrunctions to install it
- if you have a older version then update it:
brew update
now you can install gcc-4.2 and create a symbolink link where is aspected by the build system
brew tap homebrew/dupes
brew install apple-gcc42
sudo ln -s /usr/local/bin/gcc-4.2 /usr/bin/gcc-4.2
now you're ready to successfully install rails
gem install rails
You should get output something like this
Fetching: i18n-0.6.1.gem (100%) Fetching: activesupport-3.2.8.gem (100%) Fetching: builder-3.0.4.gem (100%) Fetching: activemodel-3.2.8.gem (100%) Fetching: rack-cache-1.2.gem (100%) Fetching: rack-test-0.6.2.gem (100%) Fetching: journey-1.0.4.gem (100%) Fetching: hike-1.2.1.gem (100%) Fetching: sprockets-2.1.3.gem (100%) Fetching: erubis-2.7.0.gem (100%) Fetching: actionpack-3.2.8.gem (100%) Fetching: arel-3.0.2.gem (100%) Fetching: tzinfo-0.3.34.gem (100%) Fetching: activerecord-3.2.8.gem (100%) Fetching: activeresource-3.2.8.gem (100%) Fetching: polyglot-0.3.3.gem (100%) Fetching: treetop-1.4.12.gem (100%) Fetching: mail-2.4.4.gem (100%) Fetching: actionmailer-3.2.8.gem (100%) Fetching: rack-ssl-1.3.2.gem (100%) Fetching: railties-3.2.8.gem (100%) Fetching: rails-3.2.8.gem (100%) Successfully installed i18n-0.6.1 Successfully installed activesupport-3.2.8 Successfully installed builder-3.0.4 Successfully installed activemodel-3.2.8 Successfully installed rack-cache-1.2 Successfully installed rack-test-0.6.2 Successfully installed journey-1.0.4 Successfully installed hike-1.2.1 Successfully installed sprockets-2.1.3 Successfully installed erubis-2.7.0 Successfully installed actionpack-3.2.8 Successfully installed arel-3.0.2 Successfully installed tzinfo-0.3.34 Successfully installed activerecord-3.2.8 Successfully installed activeresource-3.2.8 Successfully installed polyglot-0.3.3 Successfully installed treetop-1.4.12 Successfully installed mail-2.4.4 Successfully installed actionmailer-3.2.8 Successfully installed rack-ssl-1.3.2 Successfully installed railties-3.2.8 Successfully installed rails-3.2.8 22 gems installed Installing ri documentation for i18n-0.6.1... Building YARD (yri) index for i18n-0.6.1... Installing ri documentation for activesupport-3.2.8... Building YARD (yri) index for activesupport-3.2.8... Installing ri documentation for builder-3.0.4... Building YARD (yri) index for builder-3.0.4... Installing ri documentation for activemodel-3.2.8... Building YARD (yri) index for activemodel-3.2.8... Installing ri documentation for rack-cache-1.2... Building YARD (yri) index for rack-cache-1.2... Installing ri documentation for rack-test-0.6.2... Building YARD (yri) index for rack-test-0.6.2... Installing ri documentation for journey-1.0.4... Building YARD (yri) index for journey-1.0.4... Installing ri documentation for hike-1.2.1... Building YARD (yri) index for hike-1.2.1... Installing ri documentation for sprockets-2.1.3... Building YARD (yri) index for sprockets-2.1.3... Installing ri documentation for erubis-2.7.0... Building YARD (yri) index for erubis-2.7.0... Installing ri documentation for actionpack-3.2.8... Building YARD (yri) index for actionpack-3.2.8... Installing ri documentation for arel-3.0.2... Building YARD (yri) index for arel-3.0.2... Installing ri documentation for tzinfo-0.3.34... Building YARD (yri) index for tzinfo-0.3.34... Installing ri documentation for activerecord-3.2.8... Building YARD (yri) index for activerecord-3.2.8... Installing ri documentation for activeresource-3.2.8... Building YARD (yri) index for activeresource-3.2.8... Installing ri documentation for polyglot-0.3.3... Building YARD (yri) index for polyglot-0.3.3... Installing ri documentation for treetop-1.4.12... Building YARD (yri) index for treetop-1.4.12... Installing ri documentation for mail-2.4.4... Building YARD (yri) index for mail-2.4.4... Installing ri documentation for actionmailer-3.2.8... Building YARD (yri) index for actionmailer-3.2.8... Installing ri documentation for rack-ssl-1.3.2... Building YARD (yri) index for rack-ssl-1.3.2... Installing ri documentation for railties-3.2.8... Building YARD (yri) index for railties-3.2.8... Installing ri documentation for rails-3.2.8... Building YARD (yri) index for rails-3.2.8... Installing RDoc documentation for i18n-0.6.1... Installing RDoc documentation for activesupport-3.2.8... Installing RDoc documentation for builder-3.0.4... Installing RDoc documentation for activemodel-3.2.8... Installing RDoc documentation for rack-cache-1.2... Installing RDoc documentation for rack-test-0.6.2... Installing RDoc documentation for journey-1.0.4... Installing RDoc documentation for hike-1.2.1... Installing RDoc documentation for sprockets-2.1.3... Installing RDoc documentation for erubis-2.7.0... Installing RDoc documentation for actionpack-3.2.8... Installing RDoc documentation for arel-3.0.2... Installing RDoc documentation for tzinfo-0.3.34... Installing RDoc documentation for activerecord-3.2.8... Installing RDoc documentation for activeresource-3.2.8... Installing RDoc documentation for polyglot-0.3.3... Installing RDoc documentation for treetop-1.4.12... Installing RDoc documentation for mail-2.4.4... Installing RDoc documentation for actionmailer-3.2.8... Installing RDoc documentation for rack-ssl-1.3.2... Installing RDoc documentation for railties-3.2.8... Installing RDoc documentation for rails-3.2.8...
回答2:
@Franco is correct: the "native extension" build scripts expect /usr/bin/gcc-4.2, which does not exist in OS X Mountain Lion.
- If you upgraded to Mountain Lion from a prevoius OS X version, then you may already have gcc. In that case, just create a symlink to gcc:
sudo ln -s /usr/bin/gcc /usr/bin/gcc-4.2 - If you have a fresh install of Mountain Lion, then you may not have gcc at all. In that case, you would need to install gcc as @Franco explains.
This is not specifically a "rails" gem issue. Any gem that builds "native extensions" fails:
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension. [...] You have to install development tools first.
In my case, I was trying to install octopress, which depends on something called RedCloth.
回答3:
I ran into this issue as well, with Mountain Lion. The gem that was failing installation was json. To fix it, I installed the xcode CLI tools and then just symlinked the installed gcc (i686-apple-darwin11-llvm-gcc-4.2) as /usr/bin/gcc-4.2. Once this was done, it just worked.
While trying to install another gem, I ran into a similar issue where the native build step complained about missing g++-4.2. I symlinked this exactly the same as I did with gcc-4.2 above, and it worked.
UPDATE: OSX Mavericks with latest RVM
With the latest OSX 10.9 and latest RVM, these issues seem to have gone away. So, time to upgrade.
回答4:
Try working through this first
He assumes you already have homebrew. If you don't you can get it from here
来源：https://stackoverflow.com/questions/11802918/error-failed-to-build-gem-native-extension-when-installing-rails-on-mac-mountia