rbenv and gems that require C extensions - ruby

Question

So I'm trying to install the audite gem, but having issues with rbenv:
$ bundle install
Fetching gem metadata from https://rubygems.org/...
Installing audite (0.3.0)
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
/opt/boxen/rbenv/versions/1.9.3-p448/bin/ruby extconf.rb
checking for mpg123.h... no
*** 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.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/opt/boxen/rbenv/versions/1.9.3-p448/bin/ruby
please install mpg123 headers
Gem files will remain installed in /opt/boxen/rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/audite-0.3.0 for inspection.
Results logged to /opt/boxen/rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/audite-0.3.0/ext/mpg123/gem_make. out
An error occurred while installing audite (0.3.0), and Bundler cannot continue.
Make sure that `gem install audite -v '0.3.0'` succeeds before bundling.
I know that these gems require c extensions, and I have them installed with homebrew. And if I go into the cellar for homebrew I can see the file it's looking for (mpg123.h)
/opt/boxen/homebrew/Cellar/mpg123/1.15.4/include/mpg123.h
So, is there a way to add this into the rbenv environment without just sim-linking or copying it directly into /opt/boxen/rbenv/versions/1.9.3-p448/

Answer 1

xcode-select --install
resolved it for me.

Answer 2

I ran into the same issues trying to install audite. Turns out that mkmf writes a file call mkmf.log to tell you more specifically what it does to find out if the headers are availbale or not:
>>> cat mkmf.log
have_header: checking for mpg123.h... -------------------- no
"xcrun cc -E -I. -I/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin12.0 -I. -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -g -Os -pipe -fno-common -DENABLE_DTRACE -fno-common -pipe -fno-common conftest.c -o conftest.i"
xcode-select: Error: No Xcode is selected. Use xcode-select -switch <path-to-xcode>, or see the xcode-select manpage (man xcode-select) for further information.
checked program was:
/* begin */
1: #include <mpg123.h>
/* end */
--------------------
Turns out that I hadn't had xcode installed yet; after installing it and running
xcode-select --print-path
I saw that the path was now set. Then I still had to run xcrun once to agree to Apple's licence agreements, but then the installed installed just fine!

Answer 3

Add the homebrew include directory to your path, rubygems will find it. This isn't really a problem with rbenv.
In a default install, homebrew symlinks all the include folders of the packages to /usr/local/include, in your case, those should be in /opt/boxen/homebrew/include. Just have a look around, there should a be a folder somewhere containing all includes.

Answer 4

So in the end one of the following things fixed it for me, I'm not sure which because I'd rebuild and changed my machine few times since I had this issue:
Switched to Ruby 2.0.0
Upgraded to Mavericks (which does change some
stuff with xcode stuff I believe)
Updated my Boxen/Brew to latest
version