I just upgraded my mac to OS X 10.9.8.
I got some solution when I google this problem. (Ex : install Xcode , install mysql..ect)
But that still can't fix this problem.
Try to install gem: ERROR: Error installing mysql2: ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
checking for ruby/thread.h... yes
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for rb_thread_blocking_region()... yes
checking for rb_wait_for_single_fd()... yes
checking for rb_hash_dup()... yes
checking for rb_intern3()... yes
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Using mysql_config at /usr/local/bin/mysql_config
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checking for mysql.h... yes
checking for errmsg.h... yes
checking for mysqld_error.h... yes
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Setting rpath to /usr/local/Cellar/mysql/5.6.17_1/lib
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creating Makefile
make "DESTDIR=" clean
make "DESTDIR="
compiling client.c
compiling infile.c
compiling mysql2_ext.c
compiling result.c
linking shared-object mysql2/mysql2.bundle
clang: error: unknown argument: '-multiply_definedsuppress' [-Wunused-command-line-argument-hard-error-in-future]
clang: note: this will be a hard error (cannot be downgraded to a warning) in the future
make: *** [mysql2.bundle] Error 1
make failed, exit code 2
Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/mysql2-0.3.15 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-13/2.0.0/mysql2-0.3.15/gem_make.out
The solution is sudo ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future gem install mysql2.
If anyone got same problem,you can try ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future gem install gem_name.
