title: 'configure: error: cannot compute sizeof (long long)' on scientific linux when installing ruby
body: <p>I'm trying to update my version of ruby, running on Scientific Linux, but the command:</p>
  
  <pre><code>$ rvm install ruby-2.1.6
  </code></pre>
  
  <p>fails with this error:</p>
  
  <pre><code>checking size of long long... configure: error: in `/localdisk/home/user/.rvm/src/ruby-2.1.6':
  configure: error: cannot compute sizeof (long long)
  </code></pre>
  
  <p>I also get the same error if I try to reinstall the version of ruby that was installed previously. I don't know what's changed, but I do have another machine with a very similar set up that does work. I compared the configure.log file from the working and failed installations. Here are the differences:</p>
  
  <pre><code>$ diff configure_broken.log configure_working.log 
  1c1
  &lt; [2015-09-03 14:59:13] ./configure
  ---
  &gt; [2015-09-03 14:41:20] ./configure
  3,5c3
  &lt; GEM_HOME=/localdisk/home/user/.rvm/gems/ruby-2.1.3
  &lt; PATH=/localdisk/home/user/.rvm/gems/ruby-2.1.3/bin:/localdisk/home/user/.rvm/gems/ruby-2.1.3@global/bin:/localdisk/home/user/.rvm/rubies/ruby-2.1.3/bin:/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/localdisk/home/user/.rvm/bin
  &lt; GEM_PATH=/localdisk/home/user/.rvm/gems/ruby-2.1.3:/localdisk/home/user/.rvm/gems/ruby-2.1.3@global
  ---
  &gt; PATH=/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/localdisk/home/user/.rvm/bin
  199,202c197,199
  &lt; checking gmp.h usability... yes
  &lt; checking gmp.h presence... yes
  &lt; checking for gmp.h... yes
  &lt; checking for __gmpz_init in -lgmp... yes
  ---
  &gt; checking gmp.h usability... no
  &gt; checking gmp.h presence... no
  &gt; checking for gmp.h... no
  213,218c210,525
  &lt; checking size of int... 0
  &lt; checking size of short... 0
  &lt; checking size of long... 0
  &lt; checking size of long long... configure: error: in `/localdisk/home/user/.rvm/src/ruby-2.1.6':
  &lt; configure: error: cannot compute sizeof (long long)
  &lt; See `config.log' for more details
  ---
  &gt; checking size of int... 4
  &gt; checking size of short... 2
  &gt; checking size of long... 8
  &gt; checking size of long long... 8
  &gt; checking size of __int64... 0
  </code></pre>
  
  <p>Both machines have exactly the same release info:</p>
  
  <pre><code>-bash-4.1$ cat /etc/*release
  LSB_VERSION=base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch
  Scientific Linux release 6.5 (Carbon)
  Scientific Linux release 6.5 (Carbon)
  </code></pre>
  
  <p>I have a feeling from the bit of googling I did that this might be something to do with my gcc set up. Please give me suggestions on how to debug and fix this.
  Thanks.</p>