gem install rails fails on nio4r windows7 ruby 2.3

Question

Trying to install rails on a windows 7 machine:

rubygems -v 2.5.2

ruby 2.3.3p222 (2016-11-21 revision 56859) [i386-mingw32]

installed ruby

installed devkit

ruby dk.rb init
ruby dk.rb install 

Then> gem install rails (I'll get the following error)

Failed to build gem native extension windows 7

C:\>gem install rails
Temporarily enhancing PATH to include DevKit...
Building native extensions.  This could take a while...
ERROR:  Error installing rails:
        ERROR: Failed to build gem native extension.

    current directory: C:/Ruby23/lib/ruby/gems/2.3.0/gems/nio4r-1.2.1/ext/nio4r
C:/Ruby23/bin/ruby.exe -r ./siteconf20161215-7288-1jiw6zb.rb extconf.rb
checking for unistd.h... *** 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=C:/Ruby23/bin/$(RUBY_BASE_NAME)
C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:456:in `try_do': The compiler failed to generat
e an executable file. (RuntimeError)
You have to install development tools first.
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:587:in `try_cpp'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:1091:in `block in have_header'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:942:in `block in checking_for'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:350:in `block (2 levels) in postpo
ne'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:320:in `open'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:350:in `block in postpone'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:320:in `open'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:346:in `postpone'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:941:in `checking_for'
        from C:/Ruby23/lib/ruby/2.3.0/mkmf.rb:1090:in `have_header'
        from extconf.rb:3:in `<main>'

To see why this extension failed to compile, please check the mkmf.log which can
 be found here:

  C:/Ruby23/lib/ruby/gems/2.3.0/extensions/x86-mingw32/2.3.0/nio4r-1.2.1/mkmf.lo
g

extconf failed, exit code 1

Gem files will remain installed in C:/Ruby23/lib/ruby/gems/2.3.0/gems/nio4r-1.2.
1 for inspection.
Results logged to C:/Ruby23/lib/ruby/gems/2.3.0/extensions/x86-mingw32/2.3.0/nio
4r-1.2.1/gem_make.out

C:\>ruby -v
ruby 2.3.3p222 (2016-11-21 revision 56859) [i386-mingw32]

C:\>

>

Answer 1

if anyone runs into this same issue on Windows! Here's what I did to get Rails (and nio4r) finally installed:

Downgrade Ruby 2.3.3 to Ruby 2.2.6

Install the 32bit version of the DevKit (DevKit-mingw64-32-4.7.2-20130224-1151-sfx.exe)

cd devkit 

ruby dk.rb init

ruby dk.rb review 

ruby dk.rb install 

cd \

gem install rails 

WAH LAH!

Answer 2

Downgrading to 32bit version of the DevKit (DevKit-mingw64-32-4.7.2-20130224-1151-sfx.exe) for the same ruby version (2.3.3) fixed this issue for me. I didn't have to downgrade Ruby to 2.2.6.

Thanks for pointing me in the right direction!