Facing [Undifined Reference to 'Setup'

So, Hello guys. I'm sorry for asking here. first, sorry for my bad english because I'm still learning about it. So it's my problem. I have a sketch for my project and I use a arduino Mega2560 and when I compile itu, the erros appears. Can anyone give me a solution?

Arduino: 1.8.0 Hourly Build 2016/12/21 04:34 (Windows 10), Board: "Arduino/Genuino Mega or Mega 2560, ATmega2560 (Mega 2560)"

C:\Users\user\AppData\Local\Temp\ccJsh2Jw.ltrans1.ltrans.o: In function `main':

E:\MY FILE\my folder\folder tugas\arduino-nightly\hardware\arduino\avr\cores\arduino/main.cpp:43: undefined reference to `setup'

collect2.exe: error: ld returned 1 exit status

exit status 1
Error compiling for board Arduino/Genuino Mega or Mega 2560.

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Sorry for being annoying in this forum.Thanks

Every sketch must have a setup function, even if it's empty.

pert:
Every sketch must have a setup function, even if it's empty.

Thank you so much, I watch my sketch again. And there is a typo on my void setup so it make my sketch can't compile