When warning about undocumented member functions, the reported line number is that of the class, not the undocumented member function.

For example, when generating docs for the following class:
/** A small man
*/
struct miniman { // <--------- line 3
        /// Here's some documentation
        void doc();

        void undoc(); // <--------- line 7
};

I get the following warning:

/tmp/miniman.h:3: warning: Member undoc() (function) of class miniman is not documented.

The line number should be that of the undocumented member, i.e. line 7

$ doxygen --version
1.8.11