title: .data.rel.ro+0x8 error: undefined reference to 'typeinfo for android::MediaSource'
body: <p>I cannot solve an issue while compiling my JNI source in android using ndk-build. The class which is causing error is as below:</p>
  
  <pre><code>class MxDataSource : public MediaSource
  {
      public:
            MxdataSource();
            virtual status_t start(MetaData *params);
            virtual status_t stop();
            virtual sp&lt;MetaData&gt; getFormat();
            virtual status_t read(MediaBuffer **buffer, const MediaSource::ReadOption *options));
            virtual ~MxDataSource();
            void LinkMxData(MxData* data);
            void DelinkMxData();
  };
  </code></pre>
  
  <p>Here, all the virtual methods are defined pure in <code>MediaSource</code> class. Now, when I compile it, I got the following errors :</p>
  
  <pre><code>MxDataSource.cpp(.data.rel.ro+0x8):error: undefined reference to 'typeinfo for android::MediaSource'
  MxDataSource.cpp(.data.rel.ro+0x18):error: undefined reference to 'typeinfo for android::MediaSource'
  MxDataSource.cpp(.data.rel.ro+0x54):error: undefined reference to 'typeinfo for android::MediaSource'
  </code></pre>
  
  <p>I have gone through the stackoverflow links with the similar issue but cannot solve. 
  Any direction will be grateful.</p>
  
  <p>Thanks.</p>