Installing pg gem; ERROR: Failed to build gem native extension - ruby-on-rails

Question

After updating to OS X 10.9 Mavericks I tried to start a Rails 3 app, but the connection to the PG database was not working. Checking on PGAdmin III, the database is still there and it works fine.
So I tried to reinstall the pg gem:
gem uninstall pg
gem install pg
But the last command doesn't succeed, and gives the following error:
Building native extensions. This could take a while... ERROR: Error
installing pg:
ERROR: Failed to build gem native extension.
/Users/XXX/.rvm/rubies/ruby-1.9.3-p194/bin/ruby extconf.rb checking for pg_config... yes Using config values from
/usr/local/bin/pg_config
* extconf.rb failed * Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check
the mkmf.log file for more details. You may need configuration
options.
/Users/XXX/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:381:in
`try_do': The compiler failed to generate an executable file.
(RuntimeError) You have to install development tools first. from
/Users/XXX/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:461:in
try_link0' from
/Users/XXX/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/mkmf.rb:476:in
try_link' from extconf.rb:39:in `'
I guess the problem is related to the Xcode developer tools. I updated Xcode to the latest version, but that didn't solve the problem. Do you know how to fix it?

Answer 1

You're right that the problem is related to the Xcode developer tools. It's not a bad idea to make sure you have all the developer tools installed (as opposed to solely installing gcc as mentioned in the previous answer):
Open up Xcode
In the application menu item "Xcode" select Open Developer Tool > More Developer Tools...
This takes you to a site with a bunch of software. Go ahead and download and install "Command Line Tools (OS X Mavericks) for Xcode - Late October 2013".
You will now be able to properly install the gem.
For anyone else coming to this issue off of a fresh install of the Postgres 9.3.0 app on Mac OS X Mavericks (i.e. you're not using homebrew for your Postgres installation) you may notice that even though you can build the pg gem you cannot run rake because of a dylib issue:
rake aborted!
dlopen(/Users/[USERNAME]/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/pg-0.15.1/lib/pg_ext.bundle, 9): Library not loaded: #loader_path/../lib/libpq.5.dylib
Referenced from: /Users/[USERNAME]/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/pg-0.15.1/lib/pg_ext.bundle
Reason: image not found - /Users/[USERNAME]/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/pg-0.15.1/lib/pg_ext.bundle
Unfortunately this is a problem with the current release version of 9.3.0 of Postgres. Winding back to a previous version will fix it for you:
uninstall the pg gem: gem uninstall pg
delete your 9.3.0 Postgres app by dragging it to the trash and emptying the trash
install version 9.2.2.0 of the Postgres app here: http://postgres-app.s3.amazonaws.com/PostgresApp-9-2-2-0.zip
reinstall the pg gem: gem install pg
*Thanks to the comment by jhiro009 on this thread for pointing me in the right direction on this last Postgres app part of the issue although the 9.2.4.3 version that he mentioned didn't work for me.

Answer 2

Using homebrew fixed this for me:
gem uninstall pg
brew install apple-gcc42
gem install pg
EDIT: I also manually installed "devtools"
xcode-select --install

Answer 3

On OS X Mavericks
sudo ln -s /usr/bin/llvm-gcc /usr/bin/gcc-4.2
gem uninstall pg; gem install pg;
works with homebrew Postgresql (9.3.1) installation and Apple Command Line Tools installed (pg 0.17.0).

Answer 4

None of the previous solutions worked for me (I just upgraded to Mavericks and updated XCode). Instead, I installed Postgress.app. and called
gem install pg -- --with-pg-config=/Applications/Postgres.app/Contents/MacOS/bin/pg_config

Answer 5

None of the solutions worked for me, and I didn't want to use MacPorts. Try and download the Postgres App and put it into the Application directory.
Then, specify the location of newly downloaded pg_config, which resides inside the app:
gem install pg -- --with-pg-config=/Applications/Postgres.app/Contents/MacOS/bin/pg_config
If you run in to missing headers problem, try specifying the include directory of the app:
gem install pg -- --with-pg-include='/Applications/Postgres.app/Contents/MacOS/include/'

Answer 6

If you are looking for just a quick fix, add the following to your database.yml file:
host: localhost
I had the exact problem, added that line, and now all is well.

Answer 7

I had luck following this post from the guys at New-Bamboo:
3 Quick Tips for Coding with OS X 10.9 Mavericks
After installing the xcode dev tools, the third step sorted everything out:
brew tap homebrew/versions && brew install apple-gcc42
brew link --force apple-gcc42
ln -nsf $(which gcc-4.2) /usr/bin/gcc-4.2

Answer 8

I had this problem the first time I tried to install pg. Through various trials and errors I found something that worked. Thankfully, my notes also worked when Mavericks broke everything.
Hope this helps:
Do not do any brewing.
download the enterpriseDB one-click installer, mount and run.
If it doesn't work, run it through the command line (unattended mode) and it will change the memory settings. Restart, run again.
Makes a user called postgres with the password you supply. Also installs pgadmin III.
run this in app directory:
env ARCHFLAGS="-arch x86_64" gem install pg -- --with-pg-include=/Library/PostgreSQL/9.2/include/ --with-pg-lib=/Library/PostgreSQL/9.2 sudo env ARCHFLAGS='-arch i386' gem install pg/lib/
Open pgadmin3 and create a user and password for rails, then add it to config.
psql [database_name] # to check on your db. Or use pgadmin III