make -C /lib/modules/4.8.0-36-generic/build M=/home/andrei/project modules
make[1]: Entering directory '/usr/src/linux-headers-4.8.0-36-generic'
  CC [M]  /home/andrei/project/test1.o
In file included from /home/andrei/project/test1.c:4:0:
/home/andrei/project/test1.c: In function ‘__exittest’:
/home/andrei/project/test1.c:82:13: error: return from incompatible pointer type [-Werror=incompatible-pointer-types]
 module_exit(exit_point);
             ^
./include/linux/module.h:137:11: note: in definition of macro ‘module_exit’
  { return exitfn; }     \
           ^
cc1: some warnings being treated as errors
scripts/Makefile.build:295: recipe for target '/home/andrei/project/test1.o' failed
make[2]: *** [/home/andrei/project/test1.o] Error 1
Makefile:1491: recipe for target '_module_/home/andrei/project' failed
make[1]: *** [_module_/home/andrei/project] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-4.8.0-36-generic'
Makefile:4: recipe for target 'all' failed
make: *** [all] Error 2