I was having some issues getting the mysql2 gem to install on my Windows 8.1 machine. I followed the instructions in this post:

Ruby MYSQL2 gem installation on windows 7

to install the mysql2 gem, and I did not get any error messages.

I followed this with the

bundle install

command, and confirmed that the following gems are installed (using bundle show), confirming that I have the following gems installed:

Using devise (3.2.2)
Using mysql2 (0.3.14)

Then I tried doing:

rails generate devise:install

and this is what I got:

C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/mysql2-0.3.14/lib/mysql2.rb:8:in `require': 126: The specified module could not be found.   
- C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/mysql2-0.3.14/lib/mysql2/mysql2.so (LoadError)
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/mysql2-0.3.14/lib/mysql2.rb:8:in `<top (required)>'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/bundler-1.5.1/lib/bundler/runtime.rb:76:in `require'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/bundler-1.5.1/lib/bundler/runtime.rb:76:in `block (2 levels) in require'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/bundler-1.5.1/lib/bundler/runtime.rb:72:in `each'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/bundler-1.5.1/lib/bundler/runtime.rb:72:in `block in require'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/bundler-1.5.1/lib/bundler/runtime.rb:61:in `each'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/bundler-1.5.1/lib/bundler/runtime.rb:61:in `require'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/bundler-1.5.1/lib/bundler.rb:131:in `require'
    from C:/Users/Joseph/googledrive/projects/rails/test_new_devise/config/application.rb:7:in `<top (required)>'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/railties-4.0.2/lib/rails/commands.rb:43:in `require'
    from C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/railties-4.0.2/lib/rails/commands.rb:43:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

Any ideas?

Solution:

The answer is a combination of two answers from stackoverflow, plus modifications. The stackoverflow references are:

Ruby MYSQL2 gem installation on windows 7 ...mysql2/mysql2.so: [BUG] Segmentation fault ruby 2.0.0p247

Bottom line: to get mysql2 working in a 64 bit environment with Ruby 2 on Windows 8.1, you need to do the following:

Clean up: the reason you're here is that you're probably been trying to install this gem, and it has failed, so you have some cleanup to do: gem uninstall mysql2
Download Ruby 2.0 64 bit for Windows:

http://dl.bintray.com/oneclick/rubyinstaller/rubyinstaller-2.0.0-p353-x64.exe?direct

Run the installer. Note the directory it installs to, and make sure it's in the User PATH. go to

Control Panel > System and Security > System - Advanced System Settings > Environment Variables

and make sure the path to the bin directory of the ruby install directory is in the PATH environment variable for the LOCAL user (it's also OK if it's in the SYSTEM Path environment variable)

Download the Ruby 2 64 bit Dev Kit:

http://cdn.rubyinstaller.org/archives/devkits/DevKit-mingw64-64-4.7.2-20130224-1432-sfx.exe

Run the installer and note the location of the install directory. The instructions say that once you're done with the install, you need to run the devkitvars.bat file to set the environment variables. This DOES NOT work for Windows 8.1. You need to repeat the instructions to set the local path described in #2 above, to set the path environment variable for the local user to add the ruby dev kit bin directory, and the ruby dev kit mingw bin directory. For example, if the dev kit was installed to c:\ruby2devkit, and you installed ruby2 to the C:\Ruby200-x64 directory, then your edit your path statement to look like this:
```
C:\Ruby200-x64\bin;C:\ruby2-devkit\bin;c:\ruby2-devkit\mingw\bin
```
Next you need to install the mysql-connector. DO NOT download and run the self-installer. Instead, download the zip file and unpack it. Note the directory you unpacked it to (for the purposes of this post, let's assume you unpacked it to c:\mysql-connector:

http://dev.mysql.com/downloads/file.php?id=450612

The libmysql.lib included in the MySQL Connector 64 bit is not compatible with the mingw64-gcc compiler. You need to generate mingw64 compatible libmysql.lib file.
Download the tools you need

https://structure-svm-map.googlecode.com/files/svm-map-win.zip
Unzip this file to a local directory, let's assume that you unzipped it to c:\svm-map

Edit the PATH environment path, as described earlier, to now look like this:

C:\Ruby200-x64\bin;C:\ruby2-devkit\bin;c:\ruby2-devkit\mingw\bin;c:\svm-map;C:\svm-map\python-mingw-lib

Generate the new mysql libraries:

(make sure you're running as administrator)

cd c:\mysql-connector\lib

gendef.exe libmysql.dll

dlltool -v --dllname libmysql.dll --def libmysql.def --output-lib libmysql.lib

copy libmysql.dll C:\Ruby200-x64\bin

copy libmysql.lib C:\Ruby200-x64\bin

Install the gem as follows (note the use of forward slashes instead of backslashes, it will fail if you use backslashes):

gem install mysql2 --platform=ruby -- '--with-mysql-dir="C:/mysql-connector/"'

Hope this helps, and hopefully someone will pay attention to the few Windows 8.1 users who want to do Ruby on Rails development.

When you installed the mysql2, did you download the lib files it needs?

I've not installed it on Windows 8, but Windows 7 needs to have this file to give mysql the dependencies requires to help it work. You can see various tutorials on how to do this, and I'll outline a simple overview here:

- Unzip the mysql connector file:

C:\mysql-connector-c-6.1.3-win32\ (or similar path WITHOUT any spaces)

- Run the mysql2 gem installer again:

gem uninstall mydsql
gem install mysql2 --platform=ruby -- '--with-mysql-lib="C:\mysql-connector\lib" --with-mysql-include="C:\mysql-connector\include" --with-mysql-dir="C:\mysql-connector"'

Bottom line is I think your mysql2 gem isn't loading the files it requires to run, and probably doesn't show an error because it's Windows 8