When a gem fails, where do I find the mkmf.log file?

Question

Can\'t find the \'libpq-fe.h header

** extconf.rb failed **

Could not create Makefile due to some reason, probably lack of necessary libraries and/or

Answer 1

find $GEM_HOME -name mkmf.log

or

$GEM_HOME/extensions/$arch/$ruby_version-static/$gem_name-$gem_version/mkmf.log

chruby, ruby-2.6.3:

GEM_HOME: /home/yuri/.gem/ruby/2.6.3
arch: x86_64-linux
ruby_version: 2.6.0
gem_name: openssl
gem_version: 2.0.0

/home/yuri/.gem/ruby/2.6.3/extensions/x86_64-linux/2.6.0-static/openssl-2.0.0/mkmf.log

rvm, ruby-2.6.3:

GEM_HOME: /home/yuri/.rvm/gems/ruby-2.6.3
arch: x86_64-linux
ruby_version: 2.6.0
gem_name: nokogiri
gem_version: 1.10.3

/home/yuri/.gem/ruby/2.6.3/extensions/x86_64-linux/2.6.0-static/nokogiri-1.10.3/mkmf.log