title: 'openssl/conf.h' file not found error on MacOS Sierra
body: <p>I am working on a C++ project which uses boost asio. Trying to build the libraries that use Asia,  I am getting the following error</p>
  
  <pre><code>/usr/local/include/boost/asio/ssl/detail/openssl_types.hpp:19:10: fatal error: 'openssl/conf.h' file not found
  #include &lt;openssl/conf.h&gt;
  </code></pre>
  
  <p>Looking of solutions <a href="https://stackoverflow.com/questions/34178988/openssl-ssl-h-not-found-but-installed-with-homebrew">here</a> &amp; <a href="https://stackoverflow.com/questions/23905661/on-mac-g-clang-fails-to-search-usr-local-include-and-usr-local-lib-by-def">here</a>, I tried </p>
  
  <pre><code>brew install openssl
  brew link openssl --force
  xcode-select --install
  </code></pre>
  
  <p>But didn't help.</p>
  
  <p>Doing the following also doesn't seem to work</p>
  
  <pre><code>export C_INCLUDE_PATH=/usr/local/include
  export CPLUS_INCLUDE_PATH=/usr/local/include
  </code></pre>
  
  <p>Boost version I am using is <code>boost_1_63_0</code>. I am on <code>MacOS Sierra</code> with <code>Xcode 8.3.1</code>. I have installed boost using <a href="https://brew.sh" rel="noreferrer">Homebrew</a></p>
  
  <pre><code>brew install boost
  </code></pre>
  
  <p>As I understand from other links, Xcode is looking at the wrong place for ssl headers. 
  But <strong>how can I resolve this?</strong></p>
  
  <p>I looked into my <code>/usr/local/include</code> &amp; <code>/opt/local/include</code>. 'openssl/ssl.h' is not present in either locations. But doing a <code>brew install openssl</code> says the following </p>
  
  <pre><code>Warning: openssl is a keg-only and another version is linked to opt.
  Use `brew install --force` if you want to install this version
  </code></pre>
  
  <p>Doing a <code>brew install openssl --force</code> says</p>
  
  <pre><code>Warning: openssl-1.0.2k already installed, it's just not linked.
  </code></pre>
  
  <p>Doing <code>brew link openssl --force</code> also doesn't solve the issue. </p>
  
  <p>Doig a <code>which openssl</code> returns the following:</p>
  
  <pre><code>/usr/local/bin/openssl
  </code></pre>
  
  <p><em>Please suggest</em></p>