Ok, after further thought, the last attempt wasn't going to work as the mac project files were not updated so we'll just put Guha's stuff in ifdefs.

rdf/base/src/nsRDFBaseDataSources.h

@@ -29,9 +29,13 @@
 class nsIRDFDataSource;
 class nsIRDFDataBase;
 
+#ifdef _WIN32
 // in nsMemoryDataSource.cpp
 nsresult NS_NewRDFInMemoryDataSource(nsIRDFDataSource** result);
-
+#else
+// in nsMemoryDataSource.cpp
+nsresult NS_NewRDFMemoryDataSource(nsIRDFDataSource** result);
+#endif
 // in nsSimpleDataBase.cpp
 nsresult NS_NewRDFSimpleDataBase(nsIRDFDataBase** result);
 

rdf/build/nsRDFFactory.cpp

@@ -117,7 +117,11 @@ RDFFactoryImpl::CreateInstance(nsISupports *aOuter,
             return rv;
     }
     else if (mClassID.Equals(kRDFMemoryDataSourceCID)) {
+#ifdef _WIN32
         if (NS_FAILED(rv = NS_NewRDFInMemoryDataSource((nsIRDFDataSource**) &inst)))
+#else
+        if (NS_FAILED(rv = NS_NewRDFMemoryDataSource((nsIRDFDataSource**) &inst)))
+#endif
             return rv;
     }
     else if (mClassID.Equals(kRDFStreamDataSourceCID)) {

rdf/datasource/src/nsRDFBuiltInDataSources.h

@@ -32,9 +32,13 @@ class nsIRDFDataBase;
 // in nsBookmarkDataSource.cpp
 nsresult NS_NewRDFBookmarkDataSource(nsIRDFDataSource** result);
 
+#ifdef _WIN32
 // in nsMemoryDataSource.cpp
 nsresult NS_NewRDFInMemoryDataSource(nsIRDFDataSource** result);
-
+#else
+// in nsMemoryDataSource.cpp
+nsresult NS_NewRDFMemoryDataSource(nsIRDFDataSource** result);
+#endif
 // in nsSimpleDataBase.cpp
 nsresult NS_NewRDFSimpleDataBase(nsIRDFDataBase** result);