Functions can't become inline after they have already been used. 

Either move the inline definition forward in the file or delete it entirely. 

The compiler encountered something like:

myex();
twoex() { myex(); }
inline myex() { return 2; } // error

and already used the function as an extern before it saw that it was specified as inline. This would be correct:

myex();

inline myex() { return 2; }

twoex() { myex(); }

or better:

inline myex();
inline myex() { return 2; }
twoex() { myex(); }