Fix GCC10 FTBFS by using the not-default-anymore CFLAG '-fcommon'

[samueloph]

TODO: Remove '-fcommon' from CFLAGS and address issues, reference:
Reference: https://gcc.gnu.org/gcc-10/porting_to.html#common

This commits closes #51, closes #54 and closes #56

[samueloph]

This patch is being used in the current mdk4 package on Debian, versioned 4.1+git20200420-2

[PhiLosove]

I use Ubuntu 20.10 and I got still the same issue like #51 , #54 and #56 .
If I type make -j4

/usr/bin/ld: attacks/auth_dos.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/beacon_flood.o:/opt/mdk4/src/attacks/beacon_flood.c:34: multiple definition of `bssid'; attacks/auth_dos.o:/opt/mdk4/src/attacks/auth_dos.c:50: first defined here
/usr/bin/ld: attacks/beacon_flood.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/countermeasures.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/deauth.o:/opt/mdk4/src/attacks/deauth.c:19: multiple definition of `bssid'; attacks/auth_dos.o:/opt/mdk4/src/attacks/auth_dos.c:50: first defined here
/usr/bin/ld: attacks/deauth.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/dummy.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/eapol.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/fuzzer.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/ieee80211s.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/probing.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
/usr/bin/ld: attacks/wids.o:/opt/mdk4/src/attacks/attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.h:39: first defined here
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:38: mdk4] Error 1
make[1]: Leaving directory '/opt/mdk4/src'
make: *** [Makefile:10: all] Error 2

Even if I use make CC=clang -j4

1 warning generated.
/usr/bin/ld: attacks/auth_dos.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/beacon_flood.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/beacon_flood.o:/opt/mdk4/src/attacks/beacon_flood.c:34: multiple definition of `bssid'; attacks/auth_dos.o:/opt/mdk4/src/attacks/auth_dos.c:50: first defined here
/usr/bin/ld: attacks/countermeasures.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/deauth.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/deauth.o:/opt/mdk4/src/attacks/deauth.c:19: multiple definition of `bssid'; attacks/auth_dos.o:/opt/mdk4/src/attacks/auth_dos.c:50: first defined here
/usr/bin/ld: attacks/dummy.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/eapol.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/fuzzer.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/ieee80211s.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/probing.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
/usr/bin/ld: attacks/wids.o:/opt/mdk4/src/attacks/./attacks.h:39: multiple definition of `attack_count'; attacks/attacks.o:/opt/mdk4/src/attacks/attacks.c:6: first defined here
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [Makefile:38: mdk4] Error 1
make[1]: Leaving directory '/opt/mdk4/src'
make: *** [Makefile:10: all] Error 2

With Ubuntu 20.04 there were no problems like this, is it problem with Ubuntu 20.10?
I am just a novice, ready to learn.

EDIT:

Today I tried to install mdk4 on another laptop with Ubuntu 20.10 and still the same error.

[PhiLosove]

Okay, da niemand Lust hat zu antworten und ich die Lösung selber herausgefunden habe, hier alles auf Deutsch:
Der Unterschied zwischen Ubuntu 20.04 und 20.10 ist unter anderem die gcc-Kompiler-Version. 20.04 verwendet gcc-9 und 20.10 gcc-10.
Also habe ich gcc-9 installiert und unter Ubuntu 20.10 beim kompillieren make CC=gcc-9 -j4 angegeben, ebenso bei make CC=gcc-9 install.

Solved