bugfix: Wrap newer construct to allow build on kernel <4.18

[Hurricos]

As per #676.

[Hurricos]

I'm not sure if this is correct per se, but it certainly builds fine.

[kimocoder]

Merged. Thanks!

[wideace99]

Hello.
Still not working with kernel <4.18
In my case I use kernel 4.9

make ARCH=x86_64 CROSS_COMPILE= -C /lib/modules/4.9.0-13-amd64/build M=/root/rtl8812au/rtl8812au modules
make[1]: Entering directory '/usr/src/linux-headers-4.9.0-13-amd64'
CC [M] /root/rtl8812au/rtl8812au/core/rtw_cmd.o
gcc-6: error: unrecognized command line option ‘-Wimplicit-fallthrough=0’; did you mean ‘-Wno-fallthrough’?
/usr/src/linux-headers-4.9.0-13-common/scripts/Makefile.build:309: recipe for target '/root/rtl8812au/rtl8812au/core/rtw_cmd.o' failed
make[4]: *** [/root/rtl8812au/rtl8812au/core/rtw_cmd.o] Error 1
/usr/src/linux-headers-4.9.0-13-common/Makefile:1560: recipe for target 'module/root/rtl8812au/rtl8812au' failed
make[3]: *** [module/root/rtl8812au/rtl8812au] Error 2
Makefile:152: recipe for target 'sub-make' failed
make[2]: *** [sub-make] Error 2
Makefile:8: recipe for target 'all' failed
make[1]: *** [all] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-4.9.0-13-amd64'
Makefile:2246: recipe for target 'modules' failed
make: *** [modules] Error 2

[Hurricos]

You're using gcc-6 is the problem.

[wideace99]

How can I change the gcc version ?

root@smtp:~/rtl8812au/rtl8812au# gcc --version
gcc (GCC) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

root@smtp:~/rtl8812au/rtl8812au# make make ARCH=x86_64 CROSS_COMPILE= -C /lib/modules/4.9.0-13-amd64/build M=/root/rtl8812au/rtl8812au modules make[1]: Entering directory '/usr/src/linux-headers-4.9.0-13-amd64' CC [M] /root/rtl8812au/rtl8812au/core/rtw_cmd.o gcc-6: error: unrecognized command line option ‘-Wimplicit-fallthrough=0’; did you mean ‘-Wno-fallthrough’? /usr/src/linux-headers-4.9.0-13-common/scripts/Makefile.build:309: recipe for target '/root/rtl8812au/rtl8812au/core/rtw_cmd.o' failed make[4]: *** [/root/rtl8812au/rtl8812au/core/rtw_cmd.o] Error 1 /usr/src/linux-headers-4.9.0-13-common/Makefile:1560: recipe for target '_module_/root/rtl8812au/rtl8812au' failed make[3]: *** [_module_/root/rtl8812au/rtl8812au] Error 2 Makefile:152: recipe for target 'sub-make' failed make[2]: *** [sub-make] Error 2 Makefile:8: recipe for target 'all' failed make[1]: *** [all] Error 2 make[1]: Leaving directory '/usr/src/linux-headers-4.9.0-13-amd64' Makefile:2246: recipe for target 'modules' failed make: *** [modules] Error 2 root@smtp:~/rtl8812au/rtl8812au