Unable to install on Ruby 1.9.3

[jamlen]

Attempting to install wdm to get Guard working on Windows but get this even though I do have the Ruby DevKit installed:

Installing wdm (0.1.0)
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

    C:/Ruby193/bin/ruby.exe extconf.rb
checking for main() in -lkernel32... *** 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:/Ruby193/bin/ruby
        --with-kernel32lib
        --without-kernel32lib
C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:381:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:461:in `try_link0'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:476:in `try_link'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:619:in `try_func'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:845:in `block in have_library'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:790:in `block in checking_for'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:284:in `block (2 levels) in postpone'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:254:in `open'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:284:in `block in postpone'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:254:in `open'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:280:in `postpone'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:789:in `checking_for'
        from C:/Ruby193/lib/ruby/1.9.1/mkmf.rb:840:in `have_library'
        from extconf.rb:19:in `<main>'

Gem files will remain installed in c:/src/gems/ruby/1.9.1/gems/wdm-0.1.0 for inspection.
Results logged to c:/src/gems/ruby/1.9.1/gems/wdm-0.1.0/ext/wdm/gem_make.out
An error occurred while installing wdm (0.1.0), and Bundler cannot continue.
Make sure that `gem install wdm -v '0.1.0'` succeeds before bundling.

DevKit installation verified using instructions on the wiki:

c:\src>ruby -rubygems -e "require 'json'; puts JSON.load('[42]').inspect"
[42]

[jarmo]

I have the exact same problem on Ruby 2.0.0p247. Any ideas what might be wrong here?

[jarmo]

Deleting devkit, downloading newer (correct version) of it and reinstalling it with --force option did the trick.

[34db-eagles]

I am having the same problem with ruby 2.0.0p247 and I have the latest version of devkit, currently unable to download & install wdm. Where is the force option? Or where do I use it?

[jarmo]

Force option is for installing devkit again.