[2206] Add a doc comment that getHeader() should never return NULL

src/lib/datasrc/memory/zone_table_segment.h

@@ -64,6 +64,8 @@ public:
 
     /// \brief Return the ZoneTableHeader for the zone table segment.
     ///
+    /// NOTE: This method should never return \c NULL.
+    ///
     /// \return Returns the ZoneTableHeader for this zone table segment.
     virtual ZoneTableHeader* getHeader() = 0;
 

src/lib/datasrc/tests/memory/zone_table_segment_unittest.cc

@@ -36,6 +36,7 @@ TEST(ZoneTableSegment, getHeader) {
     auto_ptr<ZoneTableSegment>
         seg(ZoneTableSegment::create((*config.get())));
 
+    // getHeader() should never return NULL.
     ZoneTableHeader* header = seg->getHeader();
     EXPECT_NE(static_cast<void*>(NULL), header);