what is meanging of gcc option "-fmessage-length"?

I am using CDT(eclipse for c language). I found that default gcc compiler options are -O0 -g3 -Wall -c -fmessage-length=0. what's the meaning of -fmessage-length? that should be -fflag, but what about message-length? I didnt find it in GCC Command-Line Options. Thanks for your consideration.