undefined reference to 'atexit' error!

[Cliff Tsai]

Hi:
    There is a error message when link .o 

    ./libgcc.a(__main.o): IN function 
'__do_global_ctors':
    __main.o(.text+0xbc)"undfined reference to 
ar'exit'
   collect2: ld returned 1 exit status.
 
  Can you help 
me!ThankS!