title: Doxygen - Inherit documentation from externally documented abstract class
body: <p>I'm writing the documentation for my C++ class which inherits from an abstract class of which the documentation is already provided externally through a tag file.</p>
  
  <p>I don't want to rewrite the documentation of several inherited functions as it would just be a copy-paste of the abstract parent ones. However, after specifying my tag file in the Doxygen configuration and enabling <code>INHERIT_DOCS</code>, the inherited documentation is still not present...</p>
  
  <p>Am I missing some other parameter or could this be a limitation of Doxygen?</p>
  
  <p>Directly processing the header file of the parent abstract class with Doxygen is working as expected (the documentation is included in the child class). Also, removing the declaration of the inherited function in my child class will add the function in the "Functions inherited from <code>ParentAbstractClass</code>"-group (but obviously not compile anymore).</p>
  
  <p>Here is my working tree:</p>
  
  <pre><code>&lt;root&gt;
      +- ParentAbstractClass/
      |    +- html/
      |    |- ParentAbstractClass.tag
      |    |- ParentAbstractClass.hpp
      +- ChildClass/
      |    +- html/
      |    |- ChildClass.hpp
      |- Doxyfile_child
  </code></pre>
  
  <p>The content of <code>ParentAbstractClass.hpp</code></p>
  
  <pre class="lang-cpp prettyprint-override"><code>/**
   * @brief Parent class
   */
  class ParentAbstractClass{
  public:
      /**
       * Inherited function
       * @param[in] arg: input argument
       */
      virtual void inheritedFunction(const int arg)=0;
  };
  </code></pre>
  
  <p>The content of <code>ChildClass.hpp</code></p>
  
  <pre class="lang-cpp prettyprint-override"><code>#include "ParentAbstractClass.hpp"
  
  /**
   * @brief Child class
   */
  class ChildClass : public ParentAbstractClass
  {
  public:
      // Following function should inherit the documentation from its parent
      virtual void inheritedFunction(const int arg); 
  };
  </code></pre>
  
  <p>And some relevant (to my opinion) options in the <code>Doxyfile_child</code>:</p>
  
  <pre><code>OUTPUT_DIRECTORY       = ChildClass
  INHERIT_DOCS           = YES
  INLINE_INHERITED_MEMB  = NO
  TAGFILES               = ParentAbstractClass/ParentAbstractClass.tag=../../ParentAbstractClass/html
  </code></pre>
  
  <p>I'm running Doxygen 1.8.14.</p>