title: Absolute path to source file in Visual Studio
body: <p>I have a source code file, <code>raven_sqlite.cpp</code>, which I use in different projects. I keep one copy of this file in a folder, <code>C:\Users\James\Documents\code\ravenset</code>, pointed to by the system environment variable <code>$RAVENROOT</code>. In this way I need only maintain one copy of the code, and all my projects can be sure to be using the same version.</p>
  
  <p>Here is how it looks in the Visual Studio properties view of <a href="https://en.wikipedia.org/wiki/Microsoft_Visual_Studio#Other_tools" rel="nofollow noreferrer">Solution&nbsp;Explorer</a>:</p>
  
  <p><img src="https://i.stack.imgur.com/BST84.jpg" alt="Enter image description here"></p>
  
  <p>Note how, although the editable property is titled relative path, the full path is the absolute path specified by the environment variable, <em>not</em> the path relative to the project directory.</p>
  
  <p>This has worked perfectly for many months for several projects.</p>
  
  <p>Suddenly this has stopped working for one project (the other projects are still working just fine).</p>
  
  <p>For the failing project, it looks like this:</p>
  
  <p><img src="https://i.stack.imgur.com/YkYbI.jpg" alt="Enter image description here"></p>
  
  <p>Not how the full path is now built by adding with the project directory and adding the environment variable, etc. The environment variable is <em>not</em> being expanded (or resolved or whatever you call that :-)</p>
  
  <p>Why has Visual&nbsp;Studio&nbsp;2008 suddenly stopped expanding the environment variable for this one project?</p>