how to use .mm extension file in the xcode compiler ?

Question

hi all

i have an application in which we have .mm extension files but when i try to compile it with the GCC 4.0 compiler it thorows some exceptions of some references that is taken by some variable from any where in the objective c ++ library than how can i set my xcode to make the compile that file

please provide the whole project setting by which i can compile the all .mm extension files to compile properly ?

thanks balraj