[developer@archlinux dsftp]$ make
make -C arm7
make[1]: Entering directory '/home/developer/Workspace/dsftp/arm7'
main.c
arm-none-eabi-gcc -MMD -MP -MF /home/developer/Workspace/dsftp/arm7/build/main.d -g -Wall -O2 -mcpu=arm7tdmi -mtune=arm7tdmi -fomit-frame-pointer -ffast-math -mthumb-interwork -DARM7 -I/home/developer/Workspace/dsftp/arm7/include -I/home/developer/Workspace/dsftp/arm7/build -I/home/developer/Workspace/dsftp/arm7/../common/dsgui-0.3/include -I/home/developer/Workspace/dsftp/arm7/../common/ -I/opt/devkitpro/libnds/include -I/home/developer/Workspace/dsftp/arm7/build -c /home/developer/Workspace/dsftp/arm7/source/main.c -o main.o
pm.c
arm-none-eabi-gcc -MMD -MP -MF /home/developer/Workspace/dsftp/arm7/build/pm.d -g -Wall -O2 -mcpu=arm7tdmi -mtune=arm7tdmi -fomit-frame-pointer -ffast-math -mthumb-interwork   -DARM7 -I/home/developer/Workspace/dsftp/arm7/include -I/home/developer/Workspace/dsftp/arm7/build -I/home/developer/Workspace/dsftp/arm7/../common/dsgui-0.3/include -I/home/developer/Workspace/dsftp/arm7/../common/ -I/opt/devkitpro/libnds/include -I/home/developer/Workspace/dsftp/arm7/build -c /home/developer/Workspace/dsftp/arm7/source/pm.c -o pm.o
ipc_libnds_extended.c
arm-none-eabi-gcc -MMD -MP -MF /home/developer/Workspace/dsftp/arm7/build/ipc_libnds_extended.d -g -Wall -O2 -mcpu=arm7tdmi -mtune=arm7tdmi -fomit-frame-pointer -ffast-math -mthumb-interwork  -DARM7 -I/home/developer/Workspace/dsftp/arm7/include -I/home/developer/Workspace/dsftp/arm7/build -I/home/developer/Workspace/dsftp/arm7/../common/dsgui-0.3/include -I/home/developer/Workspace/dsftp/arm7/../common/ -I/opt/devkitpro/libnds/include -I/home/developer/Workspace/dsftp/arm7/build -c /home/developer/Workspace/dsftp/arm7/../common/ipc_libnds_extended.c -o ipc_libnds_extended.o
/home/developer/Workspace/dsftp/arm7/../common/ipc_libnds_extended.c: In function 'extendedIPC':
/home/developer/Workspace/dsftp/arm7/../common/ipc_libnds_extended.c:47:40: warning: implicit declaration of function 'CheckStylus' [-Wimplicit-function-declaration]
   47 |  MyIPC->touched                  = (u8)CheckStylus();
      |                                        ^~~~~~~~~~~
linking arm7.elf
/opt/devkitpro/devkitARM/lib/gcc/arm-none-eabi/9.1.0/../../../../arm-none-eabi/bin/ld: ipc_libnds_extended.o: in function `extendedIPC':
/home/developer/Workspace/dsftp/arm7/../common/ipc_libnds_extended.c:47: undefined reference to `CheckStylus'
collect2: error: ld returned 1 exit status
make[2]: *** [/home/developer/Workspace/dsftp/arm7/Makefile:115: /home/developer/Workspace/dsftp/arm7/arm7.elf] Error 1
make[1]: *** [Makefile:97: build] Error 2
make[1]: Leaving directory '/home/developer/Workspace/dsftp/arm7'
make: *** [Makefile:27: arm7/arm7.elf] Error 2