unable to install unf_ext from gem

[michalejoye]

I get this error when i try to install this from gem
gem_make.log

[Cyberbeni]

It worked for me on macOS 10.14 with xcode 10 but didn't work on 10.13.6 with xcode 10, only with xcode 9.3
Xcode -> Preferences -> Locations -> Command Line Tools

[ReDetection]

happens for me on macOS 10.14 with xcode 10. in the mkmf.log it's written

In file included from conftest.c:1:
In file included from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0/ruby.h:33:
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/include/ruby-2.3.0/ruby/ruby.h:24:10: fatal error: 'ruby/config.h' file not found
#include "ruby/config.h"
         ^~~~~~~~~~~~~~~

how to investigate that?

[ReDetection]

Was able to solve this in a line

open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg

credits to https://stackoverflow.com/a/53194299/2105993