Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

I ran to this issue couples of week ago

Installing oj (2.0.2) with native extensions 
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /Users/viki/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb 
>>>>> Creating Makefile for ruby version 1.9.3 on x86_64-darwin11.4.0 <<<<<
creating Makefile

make
compiling cache.c
compiling cache8.c
compiling dump.c
compiling fast.c
compiling load.c
compiling oj.c
compiling saj.c
clang: error: unable to execute command: Segmentation fault: 11
clang: error: clang frontend command failed due to signal 2 (use -v to see invocation)
clang: note: diagnostic msg: Please submit a bug report to http://developer.apple.com/bugreporter/ and include command line arguments and all diagnostic information.
clang: note: diagnostic msg: Preprocessed source(s) and associated run script(s) are located at:
clang: note: diagnostic msg: /var/folders/qw/xj8ns4cn09jfv1x5qq1mhn7m0000gn/T/saj-4CFmfe.i
clang: note: diagnostic msg: /var/folders/qw/xj8ns4cn09jfv1x5qq1mhn7m0000gn/T/saj-4CFmfe.sh
make: *** [saj.o] Error 254


Gem files will remain installed in /Users/viki/.rvm/gems/ruby-1.9.3-p194@raynor/gems/oj-2.0.2 for inspection.
Results logged to /Users/viki/.rvm/gems/ruby-1.9.3-p194@raynor/gems/oj-2.0.2/ext/oj/gem_make.out

I could find the way to fix it. It was quite frustrated at that moment because the only way to get passed this error to start our web server again is to downgrade oj gem.

But eventually, I found the way to fix it. As I understand, this error causes by bug in llvm (Apple's gcc that comes with XCode). Here is the steps of how I fixed the issue.

First you need to install gcc4.2 with brew

brew update

brew tap homebrew/dupes

brew install apple-gcc42

Then reinstall your Ruby with this command (I use RVM)

CC=/usr/local/Cellar/apple-gcc42/4.2.1-5666.3/bin/gcc-4.2 rvm install 1.9.3-pXXX

After this you should be able to install oj or the other gems as usual.

I composed solution from many links but sorry I forgot to take note of those.