RubyとRailsをインストール後、gem puma -v '3.11.3'のインストール方法 RubyRails >ruby -v ruby 2.5.1p57 (2018-03-29 revision 63029) [x64-mingw32] >rails -v Rails 5.1.6 sns rails new sns To see why this extension failed to compile, please check the mkmf.log which can be found here: C:/Ruby25-x64/lib/ruby/gems/2.5.0/extensions/x64-mingw32/2.5.0/puma-3.11.3/mkmf.log extconf failed, exit code 1 Gem files will remain installed in C:/Ruby25-x64/lib/ruby/gems/2.5.0/gems/puma-3.11.3 for inspection. Results logged to C:/Ruby25-x64/lib/ruby/gems/2.5.0/extensions/x64-mingw32/2.5.0/puma-3.11.3/gem_make.out An error occurred while installing puma (3.11.3), and Bundler cannot continue. Make sure that `gem install puma -v '3.11.3'` succeeds before bundling. In Gemfile: puma puma -v '3.11.3' (?) gem install puma -v '3.11.3'

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* puma `gem install puma -v '3.11.3`
* `C:/Ruby25-x64/lib/ruby/gems/2.5.0/extensions/x64-mingw32/2.5.0/puma-3.11.3/mkmf.log`



`gem install puma -v '3.11.3'` `mkmf.log`