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
Then reinstall your Ruby with this command (I use RVM)brew updatebrew tap homebrew/dupesbrew install apple-gcc42
CC=/usr/local/Cellar/apple-gcc42/4.2.1-5666.3/bin/gcc-4.2 rvm install 1.9.3-pXXXAfter 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.