One of the annoyances of the MacOS platform is that whilst there’s a nice powerful UNIX underneath, there’s a rather dumb layer of top that does silly things like preventing the app store password being saved, or as I found the other day, disabling parts of the build system if the license hasn’t been accepted.

When you first setup MacOS to be useful, you need to install xcode’s build tools and libraries either via the app store, or with:

sudo xcode-select --install

However it seems if xcode gets updated via one of the routine updates, it can require that the license is re-accepted, and until that happens, it disable various builds of the build system.

I found the issue when I suddenly lost the ability to install native ruby gems, eg:

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

 /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
checking for BIO_read() in -lcrypto... *** 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=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
 --with-puma_http11-dir
 --without-puma_http11-dir
 --with-puma_http11-include
 --without-puma_http11-include=${puma_http11-dir}/include
 --with-puma_http11-lib
 --without-puma_http11-lib=${puma_http11-dir}/
 --with-cryptolib
 --without-cryptolib
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:434:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:513:in `block in try_link0'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/tmpdir.rb:88:in `mktmpdir'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:510:in `try_link0'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:534:in `try_link'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:720:in `try_func'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:950:in `block in have_library'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:895:in `block in checking_for'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:340:in `block (2 levels) in postpone'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:310:in `open'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:340:in `block in postpone'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:310:in `open'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:336:in `postpone'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:894:in `checking_for'
 from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/mkmf.rb:945:in `have_library'
 from extconf.rb:6:in `block in <main>'
 from extconf.rb:6:in `each'
 from extconf.rb:6:in `find'
 from extconf.rb:6:in `<main>'


Gem files will remain installed in /var/folders/py/r973xbbn2g57sr4l_fmb9gtr0000gn/T/bundler20151009-29854-mszy85puma-2.14.0/gems/puma-2.14.0 for inspection.
Results logged to /var/folders/py/r973xbbn2g57sr4l_fmb9gtr0000gn/T/bundler20151009-29854-mszy85puma-2.14.0/gems/puma-2.14.0/ext/puma_http11/gem_make.out
An error occurred while installing puma (2.14.0), and Bundler cannot continue.
Make sure that `gem install puma -v '2.14.0'` succeeds before bundling.

The solution is quite simple:

sudo xcodebuild -license

Why Apple thinks their build tools are so important that they require their own license to be accepted every so often is beyond me.