mysql2 gem Can't build native extensions

Question

Our intern's computer is having problems installing the mysql2 gem. We just upgraded his computer from OS X 10.6 to 10.8 (Mountain Lion). I have tried installing mysql through homebrew and through the 64 bit DMG installer. I also tried symlinking to the dev tools (as pointed out here: Not able to install some gems after mountain lion upgrade). We have Xcode (4.4) installed and the command line tools installed. We tried a reboot after installing the command line tools.

This is his PATH declaration from ~/.bashrc:

PATH=/usr/local/bin:$PATH:$HOME/.rvm/bin:/usr/local/mysql/bin # Add RVM to PATH for scripting

Symlink:

Diego-Blantons-MacBook-Pro-3:~ lmrunner07$ sudo ln -s /usr/bin/llvm-gcc-4.2 /usr/bin/gcc-4.2
Password:

Try to install gem:

Diego-Blantons-MacBook-Pro-3:~ lmrunner07$ gem install mysql2
Building native extensions.  This could take a while...
ERROR:  Error installing mysql2:
    ERROR: Failed to build gem native extension.

        /Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb
checking for rb_thread_blocking_region()... yes
checking for rb_wait_for_single_fd()... yes
checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
creating Makefile

make
compiling client.c
In file included from /Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby.h:32,
                 from ./mysql2_ext.h:8,
                 from client.c:1:
/Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby/ruby.h:105: error: size of array ‘ruby_check_sizeof_long’ is negative
/Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby/ruby.h:109: error: size of array ‘ruby_check_sizeof_voidp’ is negative
In file included from /Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby/intern.h:34,
                 from /Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby/ruby.h:1382,
                 from /Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby.h:32,
                 from ./mysql2_ext.h:8,
                 from client.c:1:
/Users/lmrunner07/.rvm/rubies/ruby-1.9.3-p194/include/ruby-1.9.1/ruby/st.h:67: error: size of array ‘st_check_for_sizeof_st_index_t’ is negative
client.c: In function ‘rb_raise_mysql2_error’:
client.c:98: warning: ISO C90 forbids mixed declarations and code
client.c: In function ‘rb_mysql_client_socket’:
client.c:590: warning: ISO C90 forbids mixed declarations and code
make: *** [client.o] Error 1


Gem files will remain installed in /Users/lmrunner07/.rvm/gems/ruby-1.9.3-p194/gems/mysql2-0.3.11 for inspection.
Results logged to /Users/lmrunner07/.rvm/gems/ruby-1.9.3-p194/gems/mysql2-0.3.11/ext/mysql2/gem_make.out

I've removed the homebrew installed mysql as well as the launch agent. Also rm -rf the gem directory (Users/lmrunner07/.rvm/gems/ruby-1.9.3-p194/gems/mysql2-0.3.11)

Answer 1

I solved this by:

1. Installing homebrew ruby <(curl -fsSk https://raw.github.com/mxcl/homebrew/go) (check out their website for useage Link)
2. Following these instructions http://robots.thoughtbot.com/post/27985816073/the-hitchhikers-guide-to-riding-a-mountain-lion
3. Reinstalling mysql with homebrew brew install mysql. (I tried installing mysql by follow these instructions http://erictarn.com/post/28269453881/how-i-installed-mysql-rvm-ruby-and-rails-on-mountain but i ran into issues later so i would recommend reinstalling mysql with homebrew.)
4. Reinstalling rvm and rails and the gems for my project (which included mysql2)

Note: When I tried to build I had a library issue, Library not loaded: libmysqlclient.18.dylib, which was fixed by running sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/lib/libmysqlclient.18.dylib (refer to Library not loaded: libmysqlclient.16.dylib error when trying to run 'rails server' on OS X 10.6 with mysql2 gem if you get the same issue.)