C:\Users\lj\Desktop\课上\main.o main.c:(.data+0x0): first defined here

This error message indicates that there is a duplicate definition of a variable or symbol in the program. The symbol or variable is defined in the file "main.omain.c" and has already been defined somewhere else in the program. To resolve this error, you should check all the files in the program and make sure that each symbol or variable is defined only once.