I'm not sure where to report this. SDK11/examples/peripheral/timer/main.c reads:
26 #include "bsp.h"
27
28 #include "nrf_drv_timer.h"
29 #include "bsp.h"
Line 29 duplicates the #include on line 26. The program builds with gcc -Wall as-is, and also when line 29 is commented out.
I have to wonder whether that would always be true, since gcc warnings tend to get pickier and pickier with each revision. (I know, the compiler authors are helping us by being so picky. Sometimes it just doesn't feel that way.)